Cell Types and Cell Modification

What’s In

In lesson 3, you have learned about the difference between prokaryotic and
eukaryotic cells according to their distinguishing features.
In this next topic, you will learn on the classification of different cell types and cell
modifications that lead to adaptation to carry out specialized functions.

What I Need to Know

There are certain characteristics that all living things
exhibit, the characteristics of life. Living things are made up of cells. They metabolize,
grow and develop, respond to stimulus, adapt to their environment and reproduce. Life
on Earth exhibits organization. The atom is smallest unit of matter, followed by
molecules, which are combinations of atoms. When these molecules are grouped
together, they ultimately form a cell. The cell is the basic unit of life. In multicellular,
organisms like plants and animals, cells are grouped as tissues to perform a specific
function. Different tissues can be grouped further and form organs. The organs form
organ systems that makes the function of the body more complex and efficient. Organs
system will then form the whole organisms. All living things exhibit organization, whether
they are unicellular or multicellular organisms.

What’s New

Direction: Arrange the words according to the levels of biological organization.

organ system organism tissue cell

What Is It

There are hundreds of types of cells, but the four main types are epithelial

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cells, connective tissue cells, muscle cells and nerve cells.

Epithelial Tissue—This type of tissue is commonly seen outside the body as coverings
or as linings of organs and cavities. Epithelial tissues are characterized by closely-joined
cells with tight junctions (i.e., a type of cell modification). Being tightly packed, tight
junctions serve as barriers for pathogens, mechanical injuries, and fluid loss.
Cells that make up epithelial tissues can have distinct arrangements:

• cuboidal—for secretion
• simple columnar—brick-shaped cells; for secretion and active absorption
• simple squamous—plate-like cells; for exchange of material through diffusion
• stratified squamous—multilayered and regenerates quickly; for protection
• pseudo-stratified columnar—single layer of cells; may just look stacked because of
varying height; for lining of respiratory tract; usually lined with cilia (i.e., a type of cell
modification that sweeps the mucus).

Figure 1: Epithelial Tissue (Source: Reece JB, U. L. (2010). Campbell Biology 10th.
San Francisco (CA).)
Connective Tissue—These tissues are composed of the following:

BLOOD —made up of plasma (i.e., liquid extracellular matrix); contains water, salts, and
dissolved proteins; erythrocytes that carry oxygen (RBC), leukocytes for defense (WBC),
and platelets for blood clotting.

CONNECTIVE TISSUE PROPER (CTP)—made up of loose connective tissue that is

found in the skin and fibrous connective tissue that is made up of collagenous fibers
found in tendons and ligaments. Adipose tissues are also examples of loose connective
tissues that store fats which functions to insulate the body and store energy.

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CARTILAGE —characterized by collagenous fibers embedded in chondroitin sulfate.
Chondrocytes are the cells that secrete collagen and chondroitin sulfate. Cartilage
functions as cushion between bones.

BONE —mineralized connective tissue made by bone-forming cells called osteoblasts

which deposit collagen. The matrix of collagen is combined with calcium, magnesium,
and phosphate ions to make the bone hard. Blood vessels and nerves are found at a
central canal surrounded by concentric circles of osteons.

Figure 2: Connective Tissue (Source: Reece JB, U. L. (2010). Campbell Biology 10th.
San Francisco (CA):.)

Muscle Tissue—These tissues are composed of long cells called muscle fibers that
allow the body to move voluntary or involuntary. Movement of muscles is a response to
signals coming from nerve cells. In vertebrates, these muscles can be categorized into
the following:
• skeletal—striated; voluntary movements
• cardiac—striated with intercalated disk for synchronized heart contraction; involuntary
• smooth—not striated; involuntary

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Figure 3: Muscle Tissue (Source: Reece JB, U. L. (2010). Campbell Biology 10th. San
Francisco (CA):.)

Nervous Tissue—These tissues are composed of nerve cells called neurons and glial
cells that function as support cells. These neurons sense stimuli and transmit electrical
signals throughout the animal body. Neurons connect to other neurons to send signals.
The dendrite is the part of the neuron that receives impulses from other neurons while
the axon is the part where the impulse is transmitted to other neurons.

Figure 4: Neurons and Glial Cells (Source: Reece JB, U. L. (2010). Campbell Biology
10th. San Francisco (CA):.)

What’s More

Direction: Match each general tissue category to the appropriate feature. Write the letter
of your choice before each number.
A. Connective tissue
B. Epithelium

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C. Muscular tissue
D. Nervous tissue

D _1. A type of tissue that would make up the majority of the brain and spinal cord?
B _2. Found in the epidermis and form the lining of internal organs such as the
intestines
A _3. Form the ligaments, tendons, fat and bone
C _4. A type of tissue that makes up majority of the heart

What I Have Learned

Direction: Identify which type of connective tissue (A-C), epithelial

tissue (D-F), and muscle tissue (G-I) is being described.

A ____(D-F)___________ transport oxygen, carbon dioxide,

nutrients and waste
through the body by travelling through the vessels called arteries and veins.
B ____(A-C)___________ is a type of dense connective tissue
that connects muscles to bones and connects bone to bone.
C ____(A-C)___________ is a type of connective tissue with one
of the hardest
extracellular matrixes that forms a protective structure used for muscle attachment.
D _____(A-C)__________ found in respiratory tract (trachea),
usually lined with cilia.
E _____(D-F)__________ found in air sacs/alveoli of the lungs,
capillaries.
F _____(G-I) __________ found in digestive tract for secretion
and active
absorption
G. (G-I) _ muscles of the heart; involuntary movements. H. (G-I)
_ involuntary contractions of digestive tract like esophagus,
stomach and intestines.
I ______(G-I) _________ striated; voluntary movements like biceps and
abdominal muscles.

What I Can Do
Direction: Give at least 4 examples of the four major tissue types.
Be as specific as possible in giving examples.

5
 Cell Cycle

What’s In

In lesson 4, you have learned about the classification of different cell types
and some cell modifications that lead to adaptation to carry out specialized functions.
In this next topic, you will learn on the phases of cell cycle and their control
points, stages of mitosis/meiosis, comparison and their role in the cell division cycle.

What I Need to Know

One of the distinct characteristics of living things is being
able to preserve themselves. Cells need to undergo cycles as part of their growth and to
repair or replace damaged parts. Cell cycle enables a living thing to continue its
existence by multiplying itself in controlled and systematic processes. This lesson will
enhance your understanding on cell cycle. This will provide learners with the concepts on
the different stages of cell cycle and the two types of cell division: mitosis and meiosis
and explain their significance on an organism.

What’s New

Direction: Label the diagram below with the following labels:

Anaphase Metaphase
Cell division (M Phase) Prophase
Cytokinesis Telophase
G1 –cell grows Interphase
G2- prepares for mitosis S- Mitosis
DNA replication
The Cell Cycle Coloring Worksheet
Then on the diagram, lightly color the G1 phase light GREEN, the S phase
dark BLUE, the G2 phase light BLUE, and the stages of mitosis VIOLET. Color the
arrows indicating all of the interphases in BLUE. Color the part of the arrow indicating
mitosis PURPLE and the part of the arrow indicating cytokinesis light VIOLET.

6
 What Is It

Cell Division—involves the distribution of identical genetic material or DNA to two

daughter cells. What is most remarkable is the fidelity with which the DNA is passed
along, without dilution or error, from one generation to the next. Cell Division functions in
reproduction, growth, and repair.

Core Concepts:
• All organisms consist of cells and arise from preexisting cells.
• Mitosis is the process by which new cells are generated.
• Meiosis is the process by which gametes are generated for reproduction.
• The Cell Cycle represents all phases in the life of a cell.
• DNA replication (S phase) must precede mitosis so that all daughter cells receive the
same complement of chromosomes as the parent cell.
• The gap phases separate mitosis from S phase. This is the time when molecular
signals mediate the switch in cellular activity.
• Mitosis involves the separation of copied chromosomes into separate cells.
• Unregulated cell division can lead to cancer.
• Cell cycle checkpoints normally ensure that DNA replication and mitosis occur only
when conditions are favorable and the process is working correctly.
• Mutations in genes that encode cell cycle proteins can lead to unregulated growth,
resulting in tumor formation and ultimately invasion of cancerous cells to other organs.

The Cell Cycle control system is driven by a built-in clock that can be adjusted by
external stimuli (i.e., chemical messages).

7
Checkpoint—a critical control point in the Cell Cycle where ‗stop‘ and ‗go-
ahead‘ signals can regulate the cell cycle.
• Animal cells have built-in ‗stop‘ signals that halt the cell cycles and checkpoints until
overridden by ‗go-ahead‘ signals. • Three major checkpoints are found in the G1, G2,
and M phases of the Cell Cycle.

The G1 Checkpoint—the Restriction Point

• The G1 checkpoint ensures that the cell is large enough to divide and that enough
nutrients are available to support the resulting daughter cells.
• If a cell receives a ‗go-ahead‘ signal at the G1 checkpoint, it will usually continue
with the Cell Cycle. • If the cell does not receive the ‗go-ahead‘ signal, it will exit the
Cell Cycle and switch to a non-dividing state called G0.
• Most cells in the human body are in the G0 phase.
The G2 Checkpoint—ensures that DNA replication in S phase has been successfully
completed.
The Metaphase Checkpoint—ensures that all of the chromosomes are attached to the
mitotic spindle by a kinetochore.
Kinase—a protein which activates or deactivates another protein by phosphorylating
them. Kinases give the ‗go-ahead‘ signals at the G1 and G2 checkpoints. The
kinases that drive these checkpoints must themselves be activated.
• The activating molecule is a cyclin, a protein that derives its name from its cyclically
fluctuating concentration in the cell. Because of this requirement, these kinases are
called cyclin-dependent kinases or CDKs.
• Cyclins accumulate during the G1, S, and G2 phases of the Cell Cycle.
• By the G2 checkpoint, enough cyclin is available to form MPF complexes (aggregations
of CDK and cyclin) which initiate mitosis.
• MPF functions by phosphorylating key proteins in the mitotic sequence.
• Later in mitosis, MPF switches itself off by initiating a process which leads to the
destruction of cyclin. • CDK, the non-cyclin part of MPF, persists in the cell as an
inactive form until it associates with new cyclin molecules synthesized during the
interphase of the next round of the Cell Cycle.

Discuss the stages of mitosis and meiosis.

Mitosis (apparent division)—is nuclear division; the process by which the nucleus
divides to produce two new nuclei. Mitosis results in two daughter cells that are
genetically identical to each other and to the parental cell from which they came.
Cytokinesis—is the division of the cytoplasm. Both mitosis and cytokinesis last for
around one to two hours.
Prophase—is the preparatory stage, during prophase, centrioles move toward opposite
sides of the nucleus.

• The initially indistinct chromosomes begin to condense into visible threads.

• Chromosomes first become visible during early prophase as long, thin, and intertwined
filaments but by late prophase, chromosomes are more compacted and can be clearly
discerned as much shorter and rod-like structures.
• As the chromosomes become more distinct, the nucleoli also become more distinct. By
the end of prophase, the nucleoli become less distinct, often disappearing altogether.

Metaphase—is when chromosomes become arranged so that their centromeres

become aligned in one place, halfway between the two spindle poles. The long axes of

8
the chromosomes are 90 degrees to the spindle axis. The plane of alignment is called
the metaphase plate.

Anaphase—is initiated by the separation of sister chromatids at their junction point at

the centromere. The daughter chromosomes then move toward the poles.

Telophase—is when daughter chromosomes complete their migration to the poles. The
two sets of progeny chromosomes are assembled into two-groups at opposite ends of
the cell. The chromosomes uncoil and assume their extended form during interphase. A
nuclear membrane then forms around each chromosome group and the spindle
microtubules disappear. Soon, the nucleolus reforms.
Meiosis—reduces the amount of genetic information. While mitosis in diploid cells
produces daughter cells with a full diploid complement, meiosis produces haploid
gametes or spores with only one set of chromosomes. During sexual reproduction,
gametes combine in fertilization to reconstitute the diploid complement found in parental
cells. The process involves two successive divisions of a diploid nucleus.

First Meiotic Division The first meiotic division results in reducing the number of
chromosomes (reduction division). In most cases, the division is accompanied by
cytokinesis.

Prophase I—has been subdivided into five substages: leptonema, zygonema,

pachynema, diplonema, and diakinesis.
• Leptonema—Replicated chromosomes have coiled and are already visible. The
number of chromosomes present is the same as the number in the diploid cell.
• Zygonema—Homologue chromosomes begin to pair and twist around each other in
a highly specific manner. The pairing is called synapsis. And because the pair consists
of four chromatids it is referred to as bivalent tetrad.
• Pachynema—Chromosomes become much shorter and thicker. A form of physical
exchange between homologues takes place at specific regions. The process of physical
exchange of a chromosome region is called crossing-over. Through the mechanism of
crossing-over, the parts of the homologous chromosomes are recombined (genetic
recombination).
• Diplonema—The two pairs of sister chromatids begin to separate from each other.
It is at this point where crossing-over is shown to have taken place. The area of contact
between two non-sister chromatids, called chiasma, become evident.
• Diakinesis—The four chromatids of each tetrad are even more condensed and the
chiasma often terminalize or move down the chromatids to the ends. This delays the
separation of homologous chromosomes.

In addition, the nucleoli disappear, and the nuclear membrane begins to break down.

Metaphase I—The spindle apparatus is completely formed and the microtubules are
attached to the centromere regions of the homologues. The synapsed tetrads are
found aligned at the metaphase plate (the equatorial plane of the cell) instead of only
replicated chromosomes.

Anaphase I—Chromosomes in each tetrad separate and migrate toward the opposite
poles. The sister chromatids (dyads) remain attached at their respective centromere
regions.

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Telophase I—The dyads complete their migration to the poles. New nuclear membranes
may form. In most species, cytokinesis follows, producing two daughter cells. Each has a
nucleus containing only one set of chromosomes (haploid level) in a replicated form.

Second Meiotic Division The events in the second meiotic division are quite similar to
mitotic division. The difference lies, however, in the number of chromosomes that each
daughter cell receives. While the original chromosome number is maintained in mitosis,
the number is reduced to half in meiosis.

Prophase II—The dyads contract.

Metaphase II—The centromeres are directed to the equatorial plate and then divide.
Anaphase II—The sister chromatids (monads) move away from each other and migrate
to the opposite poles of the spindle fiber.
Telophase II—The monads are at the poles, forming two groups of chromosomes. A
nuclear membrane forms around each set of chromosomes and cytokinesis follows. The
chromosomes uncoil and extend.

Cytokinesis—The telophase stage of mitosis is accompanied by cytokinesis. The two

nuclei are compartmentalized into separate daughter cells and complete the mitotic cell
division process. In animal cells, cytokinesis occurs by the formation of a constriction in
the middle of the cell until two daughter cells are formed. The constriction is often called
cleavage, or cell furrow. However, in most plant cells this constriction is not evident.
Instead, a new cell membrane and cell wall are assembled between the two nuclei to
form a cell plate. Each side of the cell plate is coated with a cell wall that eventually
forms the two progeny cells.

Table 1: Comparison of Mitosis and Meiosis

(Source:http://courses.washington.edu/bot113/spring/WebReadings/PdfReadings/TA
BLE_COMPARING_MITOSIS_AND.pdf)
Disorders and Diseases
• incorrect DNA copy (e.g., cancer)
• chromosomes are attached to string-like spindles and begin to move to the middle of
the cell (e.g., Down Syndrome, Alzheimer‘s, and Leukemia)

Other chromosome abnormalities:

• arise from errors in meiosis, usually meiosis I;
• occur more often during egg formation (90% of the time) than during sperm formation;

10
• become more frequent as a woman ages.
• Aneuploidy—is the gain or loss of whole chromosomes. It is the most common
chromosome abnormality. It is caused by non-disjunction, the failure of chromosomes
to correctly separate:
• homologues during meiosis I or
• sister chromatids during meiosis II

What’s More

Direction: Complete the chart by noting what occurs in each phase

Gap O (GO) It is also known as the resting phase. This phase in the cell
cycle is where the cells exist if they do not receive the go-
Interphase ahead signal at the G 1 checkpoint. Mot of the human cells
in their body are in the G0 phase.
Gap 1 (G1) This is the restriction point where it ensures that the cell is
large enough to divide and have enough nutrients in it to
support the resulting daughter cells.
S Phase It is responsible for the synthesis or replication of DNA.

Gap 2 (G2) It is where it ensures that the DNA replication in the

S phase has been successfully completed without
any problem.

Prophase The first stage of mitosis and it is the preparatory

Mitosis or M stage of the cell. In this stage you can still see the
Phase nucleus which will disappear later on

Metaphase The second stage and it is the stage where the chromosomes
arranged so that their centromeres become aligned in one
place at the center
Anaphase It is the third stage of mitosis and where the separation of
sister chromatids occurs and move towards the poles. The
chromatids are pulled by the spindle fibers.
Telophase The last stage of mitosis where the daughter chromosomes
complete their migration to the poles. The two set of
progeny chromosomes are assembled into two groups at the
opposite ends of the cell. A nuclear membrane then forms
around each chromosome group and the spindle
microtubules disappear and soon the nucleolus reforms.
Cytokinesis C  is the division of the cytoplasm that last for about one to
two hours.

What I Have Learned

11
 Direction: The diagram below shows cells in various phases of the cell cycle. Note the
cells are not arranged in the order in which the cell cycle occurs. Use the diagram to
answer questions 1-6. Write you answer in CAPITAL letters.

1. _D _Interphase (G2) 4 ___C______ Metaphase

2. _ A _Prophase 5. _ E Anaphase

3. _ F _Prometaphase 6 ____B_____ Telophase & Cytokinesis

What I Can Do

Direction: Gene mutations in a cell can result in uncontrolled cell division, called cancer.
Exposure of cells to certain chemicals and radiation increases mutations and thus
increases the chance of cancer. Research on the causes of cancers and
disorders/diseases that result from the malfunction of the cell during the cell cycle and
answer the following questions.

1. Define cancer
- Cancer is a collective name for many different diseases caused by a common mechanism:
uncontrolled cell division. Despite the redundancy and overlapping levels of cell-cycle control, errors
occur. One of the critical processes monitored by the cell-cycle checkpoint surveillance mechanism is
the proper replication of DNA during the S phase. Even when all of the cell-cycle controls are fully
functional, a small percentage of replication errors (mutations) will be passed on to the daughter cells. If
one of these changes to the DNA nucleotide sequence occurs within a gene, a gene mutation results. All
cancers begin when a gene mutation gives rise to a faulty protein that participates in the process of cell
reproduction. The change in the cell that results from the malformed protein may be minor. Even minor
mistakes, however, may allow subsequent mistakes to occur more readily. Over and over, small,
uncorrected errors are passed from parent cell to daughter cells and accumulate as each generation of
cells produces more non-functional proteins from uncorrected DNA damage. Eventually, the pace of the
cell cycle speeds up as the effectiveness of the control and repair mechanisms decreases. Uncontrolled
growth of the mutated cells outpaces the growth of normal cells in the area, and a tumor can result.

2. What are the causes of cancer?

- Tobacco products Tobacco products are

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 projected to cause 1 billion deaths this century,
many from cancer. Tobacco use is estimated to
cause 22% of cancers worldwide and
contributes to multiple other diseases.
Laboratory tests cannot yet determine the
potential long-term effects of novel electronic
nicotine delivery systems on cancer risk.
- Infectious agents and chronic infections are the
cause of about 13% of cancers worldwide, or
2.2 million cases per year, particularly in low-
and middle-income countries such as in sub-
Saharan Africa:
The bacterium is responsible for some stomach
cancers. Treatment by a combination of anti-
microbial drugs is potentially preventive;
Thirteen sexually transmitted mucosal human
papillomavirus (HPV) subtypes are established
human carcinogens, they are responsible for
cervical cancers as well as other anogenital and
oropharyngeal cancers. Vaccination against
human papillomaviruses occurs in more than 80
countries;
Chronic infection with hepatitis B virus and
hepatitis C virus accounts for the majority of
cases of liver cancer. Vaccines and antiviral
agents can be effective.
- Alcohol consumption
Alcohol consumption is associated to 3.0 million
deaths per year globally or 4.2% of all cancer
deaths: oral cavity, oropharynx, hypopharynx,
oesophagus ( squamous cell carcinoma ),
colon, rectum, liver and intrahepatic bile duct,
larynx, and female breast (both premenopausal
and postmenopausal. In particular, people with
an enzymatic variant that is prevalent in eastern
Asian populations have a higher risk of cancers
of the upper aero-digestive tract and of
colorectal cancer
- Despite the evidence of the causal relationship
between alcohol consumption and the
development of cancer, the majority of the
general population is unaware of it.

Summary

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 The importance of cell cycle is very evident that the growth and sustainability of
multicellular organisms depend on this process. Cells that are damaged and lost will be
replenished when cells divide. Errors in mitosis lead to an incorrect copy of the DNA
which may produce deadly functional consequences depending on the error. The
positive correlation with the malfunction of these processes to the onset of major
diseases such as cancer, stroke, atherosclerosis, inflammation, and some
neurodegenerative disorders in increasingly proven in various studies.

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 Assessment: (Post-Test)

Direction: Select the letter of your choice. Write it in CAPITAL letters. Your answers should be written
on a separate sheet of paper.

1. Which level of organization is the basic unit of life?

A. Cell
B. Tissue
C. Organ
D. System
2. Which of the following is NOT a postulate of a unified cell theory?
A. All living things are composed of cells
B. Cells are the basic unit of life
C. All cells undergo complete development
D. All new cells arise from existing cells
3. Who coined the term cell for the box like structure he observed when viewing cork tissue? A.
Matthias Schleiden
B. Theodor Schwann
C. Rudolf Virchow
D. Robert Hooke
4. In many cells, the structure that controls the cell activities is the . A. Cell Membrane
B. Organelle
C. Nucleolus D. Nucleus
5. Which part of the cell serves as venue for cellular respiration and is known as the powerhouse of
the cell?
A. Nucleolus
B. Chromosome
C. Mitochondrion D. Nucleus
6. Which type of tissue would be found in the epidermis and form the lining of internal organs such
as the intestines?
A. Nervous tissue
B. Muscular tissue
C. Connective tissue D. Epithelial tissue
7. The process by which the nucleus divides to produce two new nuclei that results in two
daughter cells that are genetically identical to each other and to the parental cell from which
they came.
A. Meiosis
B. Interphase
C. Mitosis
D. Cytokinesis
8. A type of passive transport which relies on carrier proteins in order for the substances to move
down their concentration gradient.
A. Active transport
B. Facilitated diffusion
C. Osmosis
D. Sodium-potassium pump
 44
9. Which of the following is an example of passive transport which occurs when particles move from
an area of higher concentration to an area of lower concentration?
A. Phagocytosis
B. Pinocytosis
C. Diffusion
D. Osmosis
10. This process utilizes additional metabolic energy against the concentration gradient to move
molecules across the membrane from a region of lower concentration to a region of higher
concentration.
A. Active Transport
B. Passive Transport
C. Osmosis
D. Exocytosis

Lesson
Transport Mechanisms
45
 6
What I Need to Know

• Learning Competencies:
1. Describe the structural components of the cell membrane
(STEM_BIO11/12-Ig-h-11)
2. Relate the structure and composition of the cell membrane to its function
(STEM_BIO11/12-Ig-h-12)
3. Explain transport mechanisms in cells (diffusion, osmosis, facilitated transport,
active transport) (STEM_BIO11/12-Ig-h-13)
4. Differentiate exocytosis and endocytosis (STEM_BIO11/12-Ig-h-14)

• Performance Standards:
The learners should be able to construct a cell membrane model from
indigenous or recyclable materials.

• Introduction:
With the pandemic today in the Philippines, you can just imagine our
Cagayan de Oro‘s front liners and law enforcers at the check points of a city or
security guards at the mall entrances (Fig. 7.a) as plasma membranes
(cell membranes) which have a lot of things to do such as permitting who‘ll
enter the establishment (represents the cell) or not and even exiting is checked
as well; Carrying goods in a truck or individuals on a motorcycle towards a
particular cordoned area which depicts different means or ways on how
materials are transported in and out of the cell - thus the transport
mechanisms.

In cellular biology, membrane transport refers to the collection of

mechanisms that regulate the passage of solutes such as ions and small
molecules through biological membranes, which are lipid bilayers that contain
proteins embedded in them.
Plasma membrane (Cell Membrane) plays a vital role in the transport
mechanisms and separates the living cell from its surroundings. To perform
these roles, it needs lipids, which make a semi-permeable barrier between the
cell and its environment. It also needs proteins, which are involved in cross-
membrane transport and cell communication, and carbohydrates (sugars and
sugar chains), which decorate both the proteins and lipids and help cells
recognize each other.

46
 Fig. 7.a Even in a mall or at the checkpoints, the people and objects move from one
location to another; they cross or are contained within certain boundaries. Analogously, a
cell membrane‘s functions involve movement within the cell and across the boundaries in
the process of intracellular and intercellular activities. Just like the law enforcers or security
guards, they allow some substances to pass through, but not others.

1.1 Structural Components of the Cell Membrane

What I Know

Write the letter of the best answer in the blank.

_1. Which plasma membrane component can be either found on its surface or
embedded in the membrane structure?
a. protein
b. cholesterol
c. carbohydrate
d. phospholipid

_2. What is the primary function of carbohydrates attached to the exterior of cell
membranes?
a. identification of the cell
b. flexibility of the membrane
c. strengthening the membrane
d. channels through membrane
_3. Which characteristic of a phospholipid contributes to the fluidity of the
membrane?
a. its head
b. cholesterol
c. a saturated fatty acid tail
d. double bonds in the fatty acid tail

_4. Which interacts to hydrophilic and hydrophobic environments? a.

protein
b. cholesterol
47
 c. phospholipid
d. carbohydrate

_5. Carbohydrates is found outside the surface of the cell and bounded with? a. lipid or
protein
b. phospholipid
c. glycoprotein
d. glycolipid

Provide the description of each structural components of the cell membrane regarding its
location and features inside the empty blanks.

COMPONENT LOCATION FEATURE/FUNCTION

• the most abundant lipid in the
Phospholipids Main fabric of the membrane plasma membrane
6. •are amphipathic molecules
_

Cholesterol 7. Tucked between the Dampen effects of temperature

hydrophobic
tails of the membrane
phospholipids

Integral Proteins Embedded in the 8. Such functions

phospholipid bilayer; may include channeling
or may not extend through or transporting
both layers molecules across
the membrane. 
On the inner or outer
Peripheral surface of the phospholipid 9. Peripheral
Proteins bilayer, but not embedded membrane
in its hydrophobic Core proteins are
membrane
proteins that
adhere only
temporarily to the
biological
membrane with
which they are
associated. 
• Cell recognition
Carbohydrate 10. on the outer • Effective interaction with the
Chains surface of the plasma acqueous environment
membrane

48
 What’s In

• REVIEW: The Structural Components of the Cell Membrane

The modern understanding of the cellular or plasma membrane is referred to as

the fluid mosaic model or fluid mosaics of lipids and proteins. It is composed of a bilayer
of phospholipids, with their hydrophobic, fatty acid tails in contact with each other (Fig.
7.d). The landscape of the membrane is studded with proteins, some of which span the
membrane. Some of these proteins serve to transport materials into or out of the cell.
Carbohydrates are attached to some of the proteins and lipids on the outward-facing
surface of the membrane (Fig. 7.b.), forming complexes which function is to identify the
cell to other cells. Cell membranes enclose and define the borders of cells, but rather
than being a static bag, they are dynamic and constantly in flux.

Fig. 7.b. Structural Component of Cellular Membrane

Fig. 7.c. In 1935, Davson-Danielli, the sandwich model of membrane structure stated that the
membrane was made up of a phospholipid bilayer sandwiched between two protein layers.

49
Fig. 7.d. In 1972, S. J. Singer and G. Nicolson proposed that the membrane is a mosaic of proteins
dispersed within the bilayer, with only the hydrophilic regions exposed to water.

The Fluidity of the membrane is due to temperature, the configuration of the

unsaturated fatty acid tails (some kinked or form a sharp twist by double bonds), the
presence of cholesterol embedded in the membrane, and the mosaic nature of the
proteins and protein-carbohydrate combinations, which are not firmly fixed in place.

Key Takes of the Fluid Nature of the CM:

• Phospholipids in the plasma membrane can move within the bilayer (Fig. 7.e)
• Most of the lipids, and some proteins, drift laterally
• Rarely does a molecule flip-flop transversely across the membrane
Fig. 7.e.

Lateral movement occurs 107 Flip -flopping across the membrane is

times per second. rare (~ once per month).

50
• As temperatures cool, membranes switch from a fluid state to a solid state.
• The temperature at which a membrane solidifies depends on the types of lipids.
• Membranes rich in unsaturated fatty acids are more fluid than those rich in saturated
fatty acids. (Fig. 7.f.)
• Membranes must be fluid to work properly; they are usually about as fluid as salad Oil.

Fig. 7.f. The type of hydrocarbon tails in phospholipids – Affects the fluidity of the cell membrane

Fluid Viscous

Unsaturated hydrocarbon tails Saturated hydrocarbon tails

(a) Unsaturated versus

saturated hydrocarbon tails

(b) Cholesterol within the

animal cell membrane

• The steroid cholesterol has different effects on membrane fluidity at different

temperatures.
• At warm temperatures (such as 37°C), cholesterol restrains movement of
Phospholipids.
• At cool temperatures, it maintains fluidity by preventing tight packing.
Structural Component of the Cell Membrane (Plasma Membrane)

COMPONENT LOCATION FEATURE/FUNCTION

• the most abundant lipid in
Phospholipids Main fabric of the membrane the plasma membrane
• are amphipathic
molecules

51
 Tucked between the hydrophobic
Cholesterol Dampen effects of
tails of the membrane
temperature
phospholipids

Embedded in the phospholipid

Integral Proteins Transport of substance
bilayer; may or may not extend
through membrane
through both layers
On the inner or outer surface of
Peripheral the phospholipid bilayer, but not Cell recognition
Proteins embedded in its hydrophobic
core
Attached to proteins or lipids on • Cell recognition
Carbohydrate the extracellular side of the • Effective interaction with
Chains membrane (forming glycoproteins the acqueous environment
and glycolipids

Terminology:
Amphiphilic or Amphipathic
• molecule possessing a polar or charged area and a nonpolar or uncharged area
capable of interacting with both hydrophilic and hydrophobic environments

Fluid mosaic model

• describes the structure of the plasma membrane as a mosaic of components including
phospholipids, cholesterol, proteins, glycoproteins, and glycolipids (sugar chains
attached to proteins or lipids, respectively), resulting in a fluid character (fluidity)

Glycolipid
• combination of carbohydrates and lipids

Glycoprotein
• combination of carbohydrates and proteins

Hydrophilic
• molecule with the ability to bond with water; ―water-loving‖

Hydrophobic
• molecule that does not have the ability to bond with water; ―water-hating‖
Integral protein
• protein integrated into the membrane structure that interacts extensively with the
hydrocarbon chains of membrane lipids and often spans the membrane; these proteins
can be removed only by the disruption of the membrane by detergents

Peripheral protein
• protein found at the surface of a plasma membrane either on its exterior or interior
side; these proteins can be removed (washed off of the membrane) by a high-salt wash

52
 What’s New

• Visual and Listening Activity:

1. A video link is provided ; ―Fluid mosaic model of cell membranes‖ | Biology |

by
Khan Academy (2015), https://youtu.be/cP8iQu57dQo

2. Watch and Listen carefully to the video and be able to recognize and relate to each
attributes of the structural components of the membrane.

3. Reflect on your life experiences and relate them to the lesson in the video so that you
will be able to write a story analogous to the structural components of the cell
membrane.

4. Write the story neatly on a long bond paper.

- According to this model a cell membrane is a dynamic structure rather than a

static structure. Lipid bilayer serves as a fluid ‘liquid-crystalline matrix’ in which
membrane proteins are found dispersed/embedded to give mosaic like
appearance to the membrane. In lipid bilayer, the polar phospholipid molecules
can move within the plane of the membrane. The constant movement of
phospholipid molecules gives rise to membrane fluidity and flexibility. The
membrane fluidity is highly dependent on the lipid composition of membrane
especially the proportion of saturated and unsaturated fatty acids; the unsaturated
bonds tend to increase the membrane fluidity. According to this model the
membrane proteins can also freely diffuse laterally in the plane of lipid matrix.
- Fluid mosaic model is the theorized model of certain biological membranes. One
of them is the plasma membrane. Based on this model, the plasma membrane is
a lipid bilayer of phospholipids with embedded proteins. It separates the contents
of the cell from its outside environment. It is selectively permeable, i.e. some
substances may pass through it via passive transport. Other substances would
not be able to pass through without using transport mechanisms such as carrier
proteins. The plasma membrane regulates what enters and exits the cell and the
mechanism is explained through the fluid mosaic model. Accordingly, the plasma
membrane is fluid because of its hydrophobic integral components such as lipids
and membrane proteins that move laterally or sideways throughout the
membrane. That means the membrane is not solid, but more like a ‘fluid‘.
- The membrane is depicted as mosaic because like a mosaic that is made up of
many different parts the plasma membrane is composed of different kinds of
macromolecules, such as integral proteins, peripheral proteins, glycoproteins,
phospholipids, glycolipids, and in some cases cholesterol, lipoproteins.
- According to the model, the plasma membrane is a lipid bilayer (interspersed with
proteins). It is so because of its phospholipid component that can fold in itself
creating a double layer – or bilayer – when placed in a polar surrounding, like
water. This structural feature of the membrane is essential to its functions, such
as cellular transport and cell recognition.

53
 What Is It

• Q & A Activity:

1. What happens to the plasma membrane if the weather gets cold?

- At low temperature, the fatty acid tails of the phospholipids move less and
become more rigid. This decreases the overall fluidity of the membrane, also
decreasing its permeability and potentially restricting entry of important molecules
such as oxygen and glucose into the cell.

2. Are there structural components involved in the membrane that are affected from the
rise and fall of the temperature? What are those structures?
- The principal components of a plasma membrane are lipids (phospholipids and
cholesterol), proteins, and carbohydrates attached to some of the lipids and some
of the proteins. A phospholipid is a molecule consisting of glycerol, two fatty
acids, and a phosphate-linked head group.

3. What does Fig. 7.f imply regarding the fatty acid or hydrocarbon tail‘s shape when
compared and contrasted in relation with transport mechanism? Explain your answer.
- Fatty acids consist of a carboxylic acid group and a long hydrocarbon chain,
which can either be unsaturated or saturated. A saturated fatty acid tail only
consists of carbon-carbon single bonds, and an unsaturated fatty acid has at least
one carbon-carbon double or triple bond. Fatty acids are distinguished from one
another by the lengths of their hydrocarbon tails and degrees of unsaturation. For
example, the one depicted above is palmitic acid, and it is identified by its tail
consisting of sixteen carbons and its complete lack of carbon-carbon double
bonds. Fatty acids are of utmost importance because they are our main source of
fuel and serve as primary components of membranes.

(Write your answers on a ½ crosswise intermediate paper.)

What’s More

• Drafting from Visual and Listening Activity:

1. A video link is provided ; ―Construction of the Cell Membrane‖ by Becky Polk-

Pohlman Barbara Liang; https://www.wisc-online.com/learn/natural-science/life-
science/ap1101/construction-of-the-cell-membrane

2. Watch and Listen carefully for you to be able to make a rough draft sketch of the
individual structural components of the membrane through the video clip.
54
3. Prepare your final draft sketch to me with labels of the indigenous /recyclable
materials you will utilize for each of the structural components for the next activity.

5. Write your sketch neatly on a long bond paper.

What I Have Learned

• Learning Process Activity:

Provide the best answer in the blank.

1. The modern understanding of the cellular or plasma membrane is referred to as the

fluid mosaic model

2. It is composed of a bilayer of _ phospholipids _.

3. Carbohydrates are attached to some of the proteins and lipids on the outward- facing
surface of the membrane.
4. energy, store energy, build macromolecules, and spare protein and fat for other uses
is a function of Carbohydrates.
5. The fluid nature of the membrane is due to configuration of the fatty acid tails
6. Cell membranes _ Cell membrane _ and _ plasma membrane _ the borders
of cells.

7. membrane transport refers to the collection of mechanisms that regulate the

passage of solutes.
8. Integral proteins, or integrins integrated into the membrane structure that interacts
extensively with the hydrocarbon chains of membrane lipids.

55
 What I Can Do

• Performance Activity:
Construct a cell membrane model from indigenous or recyclable materials.

1. Prepare your final draft sketch with labels of the indigenous /recyclable materials that
you will utilize for each of the structural components for this activity.

2. Prepare your indigenous /recyclable materials and tools kits to start constructing the
cell membrane model.

3. Set your output on a 2x2 sturdy and used illustration board or any platform.

4. Keep your output in a safe place and submit it on the exact date of submission to be
announced by your teacher.

1.2 The Relationship of the Structure and Composition of

the Cell Membrane to its Function

What I Know
Write the letter of the best answer in the blank.

_1. The primary function of the plasma membrane is ….

a. to protect the cell from its surroundings.
b. to provide shape and integrity to the cell.
c. to maintains the cell potential.
d. to be a fluid mosaic model.
56
 _2. What is the primary function of carbohydrates attached to the exterior of cell
membranes?
a. identification of the cell
b. flexibility of the membrane
c. strengthening the membrane
d. channels through membrane
_3. Cellular Signaling relation to the Plasma Membrane is….
a. to protect intracellular components from the extracellular environment.
b. to enclose and define the borders of the cell
c. to transmit signals via complex proteins
d. to transport materials into or out of the cell

_4. Cellular Transport Mechanism‘s relation to the Plasma Membrane is…

a. to protect intracellular components from the extracellular environment.
b. to transport materials into or out of the cell
c. to enclose and define the borders of the cell
d. to transmit signals via complex proteins

_5. Vital for cellular signalling processes that influence tissue and organ
formation
a. membrane markers
b. membrane receptors
c. glycoprotein
d. glycolipid

Provide the the Funtions related to the Structures and Compositions of the Cell Membrane
inside the empty blanks.

Structure or Component Function

6. Phospholipid bilayers are critical components
Phospholipid Bilayer of cell membranes. The lipid bilayer acts as a
barrier to the passage of molecules and ions
into and out of the cell. However, an important
function of the cell membrane is to allow
selective passage of certain substances into
and out of cells.
.7. Membrane markers allow cells to
Membrane Markers recognize one another, which is vital
for cellular signaling processes that
influence tissue and organ formation
during early development. This
marking function also plays a later
role in the “self”-versus-“non-self”
distinction of the immune response.
8. The cytoskeleton is a structure that helps cells
Cytoskeleton maintain their shape and internal organization, and

57
 it also provides mechanical support that enables
cells to carry out essential functions like division
and movement. Rather, several different
components work together to form the cytoskeleton.
9. A transmembrane protein (TP) is a type of
Transmembrane Protein integral membrane protein that spans the entirety of
the cell membrane. Many transmembrane proteins
function as gateways to permit the transport of
specific substances across the membrane.
10. Membrane receptors are specialized protein
Membrane Receptors molecules attached to or integrated into
the cell membrane. Through interaction
with specific ligands (e.g., hormones
and neurotransmitters), the receptors
facilitate communication between the
cell and the extracellular environment.

What’s In

• REVIEW: The Structure and Composition of the Cell Membrane relation to

its Function

The plasma membrane protects the cell from its external environment, mediates
cellular transport, and transmits cellular signals.

• The principal components of the plasma membrane are lipids (phospholipids

and cholesterol), proteins, and carbohydrates.
• The plasma membrane protects intracellular components from the extracellular
environment.
• The plasma membrane mediates cellular processes by regulating the materials
that enter and exit the cell.
• The plasma membrane carries markers that allow cells to recognize one
another and can transmit signals to other cells via receptors.
The plasma membrane (also known as the cell membrane or cytoplasmic
membrane) is a biological membrane that divides the interior of a cell from its outside
environment. (Figure 7.g)
The primary function of the plasma membrane is to protect the cell from its
surroundings. Composed of a phospholipid bilayer with embedded proteins, the plasma
membrane is selectively permeable to ions and organic molecules and regulates the
movement of substances in and out of cells. Plasma membranes must be very flexible in
order to allow certain cells, such as red blood cells and white blood cells, to change
shape as they pass through narrow capillaries.
The plasma membrane also plays a role in anchoring the cytoskeleton to provide
shape and integrity to the cell, and in attaching to the extracellular matrix and other cells
to help group cells together to form tissues. The membrane also maintains the cell
potential.

58
 In short, if the cell is represented today as a COVID FREE-CAGAYAN DE ORO
CITY, then the plasma membrane is the checkpoints with the frontliners and law
enforcers that provides protective and territorial structure for the city inside, depicting
separation or barrier, regulates which people leave and enter the city, and conveys
messages to and from neighbouring cities.
Just as an unguarded check point in the surrounding barrier can be a disaster for
the city in today‘s crisis, like a rupture in the plasma membrane causes the cell to lyse
and die.
Cellular Signaling/ Recognition’s relation to the Plasma Membrane
Among the most sophisticated functions of the plasma membrane is its ability to
transmit signals via complex proteins. These proteins can be receptors, which work as
receivers of extracellular inputs and as activators of intracellular processes, or markers,
which allow cells to recognize each other.

Membrane receptors provide extracellular attachment sites for effectors like

hormones and growth factors, which then trigger intracellular responses. Some viruses,
such as Human Immunodeficiency Virus (HIV), can hijack these receptors to gain entry
into the cells, causing infections.
Membrane markers allow cells to recognize one another, which is vital for cellular
signaling processes that influence tissue and organ formation during early development.
This marking function also plays a later role in the ―self‖-versus-―non- self‖
distinction of the immune response. Marker proteins on human red blood cells, for
example, determine blood type (A, B, AB, or O).

Terminology:
Receptor
• A protein on a cell wall that binds with specific molecules so that they can be
absorbed into the cell.

Cellular Transport Mechanisms’ relation to the Plasma Membrane

The movement of a substance across the selectively permeable plasma
membrane can be either ―passive‖—i.e., occurring without the input of cellular
energy —or ―active‖—i.e., its transport requires the cell to expend energy.
The cell employs a number of transport mechanisms that involve biological
membranes:
1. Passive osmosis and diffusion: transports gases (such as O 2 and CO2) and other
small molecules and ions
2. Transmembrane protein channels and transporters: transports small organic
molecules such as sugars or amino acids
3. Endocytosis: transports large molecules (or even whole cells) by engulfing them
4. Exocytosis: removes or secretes substances such as hormones or enzymes.
Fig. 7.g. Detailed Image of Cell Membrane Structure in a Cell

59
 What’s New

• Activity:

Identify the structural components of the cell membrane and provide the boxes with the
best answers

60
 1.
2.

3.
4. 7.

1. GLYCOPROTEIN:Protein with Carbohydrate attached

2. GLYCOLIPID:lipid with Carbohydrate attached
3. PERIPHERAL MEMBRANE PROTEIN
4. INTERGRAL MEMBRANE PROTEINS
5. CHOLESTEROL
6. PROTEIN CHANEL
7. PHOSPHOLIPID BILAYER
8. phospholipid bilayer

What Is It

• Q & A Activity:

1. Can you remember all the structural components of a cell membrane and be able to
list them down? If so, just list down at least 10 along with its functions.
- Phospholipid Bilayer - Phospholipid bilayers are critical components of cell membranes.
The lipid bilayer acts as a barrier to the passage of molecules and ions into and out of the
cell. However, an important function of the cell membrane is to allow selective passage of
certain substances into and out of cells
- Membrane Markers - Membrane markers allow cells to recognize one another, which is
vital for cellular signaling processes that influence tissue and organ formation during early
development. This marking function also plays a later role in the “self”-versus-“non-self”
distinction of the immune response.
- Cytoskeleton - The cytoskeleton is a structure that helps cells maintain their shape and
internal organization, and it also provides mechanical support that enables cells to carry
out essential functions like division and movement. Rather, several different components
work together to form the cytoskeleton

61
 - Transmembrane Protein - A transmembrane protein (TP) is a type of integral membrane
protein that spans the entirety of the cell membrane. Many transmembrane proteins
function as gateways to permit the transport of specific substances across the membrane
- Membrane Receptors - Membrane receptors are specialized protein molecules attached to
or integrated into the cell membrane. Through interaction with specific ligands (e.g.,
hormones and neurotransmitters), the receptors facilitate communication between the cell
and the extracellular environment
- Phospholipids are the main component of the cell membrane.
- In addition, it also contains glycolipids and sterols.
- The lipid bilayer is embedded with proteins.
- The function of the cell membrane it regulates the entry of minerals, acts as a receptor,
protects the cell, regulates the transport of substances in and out of the cell.

2. Are there structures or components related in the membrane‘s transport

mechanisms? What are those? Write at least 5 and indicate why they are related.
- One of the great wonders of the cell membrane is its ability to regulate the
concentration of substances inside the cell. These substances include ions such
as Ca++, Na+, K+, and Cl–; nutrients including sugars, fatty acids, and amino
acids; and waste products, particularly carbon dioxide (CO2), which must leave
the cell. The membrane’s lipid bilayer structure provides the first level of control.
The phospholipids are tightly packed together, and the membrane has a
hydrophobic interior. This structure causes the membrane to be selectively
permeable. A membrane that has selective permeability allows only substances
meeting certain criteria to pass through it unaided. In the case of the cell
membrane, only relatively small, nonpolar materials can move through the lipid
bilayer (remember, the lipid tails of the membrane are nonpolar). Some examples
of these are other lipids, oxygen and carbon dioxide gases, and alcohol.
However, water-soluble materials—like glucose, amino acids, and electrolytes—
need some assistance to cross the membrane because they are repelled by the
hydrophobic tails of the phospholipid bilayer.
- All substances that move through the membrane do so by one of two general
methods, which are categorized based on whether or not energy is required.
Passive transport is the movement of substances across the membrane without
the expenditure of cellular energy. In contrast, active transport is the movement of
substances across the membrane using energy from adenosine triphosphate
(ATP).
- Passive Transport In order to understand how substances move passively across
a cell membrane, it is necessary to understand concentration gradients and
diffusion. A concentration gradient is the difference in concentration of a
substance across a space. Molecules (or ions) will spread/diffuse from where they
are more concentrated to where they are less concentrated until they are equally
distributed in that space. (When molecules move in this way, they are said to
move down their concentration gradient.) Three common types of passive
transport include simple diffusion, osmosis, and facilitated diffusion.
- Simple Diffusion is the movement of particles from an area of higher
concentration to an area of lower concentration. A couple of common examples
will help to illustrate this concept. Imagine being inside a closed bathroom. If a
bottle of perfume were sprayed, the scent molecules would naturally diffuse from
the spot where they left the bottle to all corners of the bathroom, and this diffusion
would go on until no more concentration gradient remains. Another example is a
spoonful of sugar placed in a cup of tea. Eventually the sugar will diffuse
throughout the tea until no concentration gradient remains. In both cases, if the

62
 room is warmer or the tea hotter, diffusion occurs even faster as the molecules
are bumping into each other and spreading out faster than at cooler
temperatures. Having an internal body temperature around 98.6° F thus also aids
in diffusion of particles within the body.

(Write your answers on a ½ crosswise intermediate paper.)

What’s More

• Visual and Listening Activity:

1. A video link is provided ; ―Inside the Cell Membrane‖ by Amoeba Sisters (Feb 28,
2018), https://www.youtube.com/watch?v=qBCVVszQQNs

2. Watch and Listen carefully for you to be able to associate the components and
structures of the cell membrane to your household.

3. Make an analogous reflection paper of your household to the structures and

components of the cell membrane. Prioritize on the function aspect.

4. Write it on a long bond paper.

The cell membrane is important for maintaining homeostasis because it controls what
enters and leaves the cell

simple diffusion is when molecules spread from an area of high to an area of low
concentration

- a form of passive transport

- molecules travel with concentration gradient

- it is how oxygen and carbon dioxide travel across the membrane

Faciliated Diffusion - For water to travel across the cell membrane at a substantial rate,
the water molecules travel through protein channels known as aquaporins
Among the most sophisticated functions of the plasma membrane is the ability to
transmit signals by means of complex, integral proteins known as receptors. These
proteins act both as receivers of extracellular inputs and as activators of intracellular
processes. These membrane receptors provide extracellular attachment sites for
effectors like hormones and growth factors, and they activate intracellular response
cascades when their effectors are bound.

63
 What I Have Learned

• Learning Process Activity:

1. Provide insights on how the structures and components of the cell membrane is
related to its function with regards to the Celular Signalling/Recognition.

2. Give your Take Aways on Cellular Transport Mechanisms‘ relation to the Plasma
Membrane emphasizing more on its function.

3. Write it on a long bond paper.

The principal components of the plasma membrane are lipids ( phospholipids and
cholesterol), proteins, and carbohydrates.
The plasma membrane protects intracellular components from the extracellular
environment.
The plasma membrane mediates cellular processes by regulating the materials that
enter and exit the cell.
The plasma membrane carries markers that allow cells to recognize one another and
can transmit signals to other cells via receptors.
Key Terms
plasma membrane: The semipermeable barrier that surrounds the cytoplasm of a cell.
receptor: A protein on a cell wall that binds with specific molecules so that they can be
absorbed into the cell. The Plasma Membrane and Cellular Signaling Among the most
sophisticated functions of the plasma membrane is its ability to transmit signals via
complex proteins. Membrane receptors provide extracellular attachment sites for
effectors like hormones and growth factors, which then trigger intracellular responses.

What I Can Do

• Performance Activity:
1. Craft a task plan on a long bond paper regarding the tasks on what functions you can
contribute to your household during this time of crisis. Include also listing down the
house members functions contributing in your home.

2. Document this task in a week. Photos included in a separate paper or soft copy.
Template (example)
PARENT/GUARDIAN
SUN MON TUE WED THU FRI SAT Printed name,
01/21/20 _/_/20 _/_/20 _/_/20 _/_/20 _/_/20 _/_/20 Signature and Date

PortGAs D. Ace

64
 -sanitized -swept -ate Sakura -father
AM the outside mopped the Portgas
bathroom the floor with vertical
home disinfectanct planted
grounds pechay.
Sun 1/8/20

PortGAs D. Ace
-mother -kuya
Tsaunade Senku
-washed
PM sterilized bathed
the dishes -threw
the garbage Penduko
utensils our dog
Sun 1/8/20

3. Keep your output in a safe place and send it on the exact date of submission to be
announced by your teacher.

1.3 Transport Mechanisms in Cells 1.4 Endocytosis vs.

Exocytosis

What I Know

Write the letter of the best answer in the blank.

_1. Which is not a part of the transport mechanisms in cells? a.

facilitated
b. active
c. osmosis
d. excytosis

_2. What is the most direct form of transport mechanisms in cells? a.

passive
b. active
c. osmosis
d. excytosis
_3. Hydrocarbons dissolve in the lipid bilayer, except for…
a. pass the membrane
b. hydrophobic
c. non polar
d. polar

_4. Water molecules move from a region of high concentration to a region of low
concentration.
65
 a. facilitated
b. active
c. osmosis
d. diffusion

_5. Moves molecules from high to low regions of concentration with the
transmembrane protein
a. facilitated
b. active
c. osmosis
d. diffusion

Provide the right answers after the number in the boxes below for the difference between
Endocytosis and Exocytosis.

Endocytosis refers to the Exocytosis refers to….

transportation of 6. Exocytosis is the process by which cells
Definition macromolecules, move materials from within the cell into the
large particles, and polar extracellular fluid. Exocytosis occurs when a
substances into the cell from the vesicle fuses with the plasma membrane,
external environment. allowing its contents to be released outside
the cell.
Involved with …. Involved in removing waste from the cell
7. Endocytosis is the process by
Process
which cells take in substances
from outside of the cell by
engulfing them in a vesicle.
These can include things like
nutrients to support the cell or
pathogens that immune cells
engulf and destroy. The resulting
vesicle breaks off and is
transported within the cell.
Occurs by …. Occurs by constitutive and regulated secretory
8. pathway
Type
Phagocytosis;
Pinocytosis
Internal vesicles like Forms….
phagosomes are formed 9. In
Vesicle
exocytosis, membrane-
bound secretory
vesicles are carried to
the cell membrane,
where they dock and
fuse at porosomes and
their contents are
secreted into the
extracellular
environment. This
secretion is possible
because the vesicle
transiently fuses with
the plasma membrane.
66
 10. Endocytosis definition and Involved Exocytosis is the process by which
purposes. Endocytosis is the plant cells secrete polysaccharide precursors
Cell Wall
process by which cells take in for cell wall elaboration and hence cell growth.
Formation
substances from outside of the Extracellular proteins also cross the plasma
cell by engulfing them in a membrane by exocytosis, following synthesis
vesicle. Endocytosis occurs on the endoplasmic reticulum and transport
when a portion of the cell through the Golgi apparatus.
membrane folds in on itself,
encircling extracellular fluid and
various molecules or
microorganisms.
11. Pinocytosis, also known as Releasing of hormones out of the cell is an
cell drinking, is common in plant example
Example
and animal cells. During
receptor-mediated endocytosis,
macromolecules bind to
receptors along the surface of
the cell's plasma membrane.
Cholesterol uptake is an example
of receptor-mediated
endocytosis.

What’s In

• REVIEW: Transport Mechanisms in Cells (Diffusion, Osmosis,

Facilitated Transport, Active Transport) to its Function

Plasma membranes must allow certain substances to enter and leave a cell, and
prevent some harmful materials from entering and some essential materials from
leaving. In other words, plasma membranes are selectively permeable—they allow
some substances to pass through, but not others. If they were to lose this selectivity, the
cell would no longer be able to sustain itself, and it would be destroyed. Some cells
require larger amounts of specific substances. They must have a way of obtaining these
materials from extracellular fluids. This may happen passively, as certain materials move
back and forth, or the cell may have special mechanisms that facilitate transport. Some
materials are so important to a cell that it spends some of its energy, hydrolyzing
adenosine triphosphate (ATP), to obtain these materials. Red blood cells use some of
their energy doing just that. Most cells spend the majority of their energy to maintain an
imbalance of sodium and potassium ions between the cell's interior and exterior, as well
as on protein synthesis.

The most direct forms of membrane transport are passive. Passive transport is
a naturally occurring phenomenon and does not require the cell to exert any of its energy
to accomplish the movement. In passive transport, substances move from an area of
higher concentration to an area of lower concentration. A physical space in which there
is a single substance concentration range has a concentration gradient.

Selective Permeability

67
 Plasma membranes lack symmetry: the membrane's exterior is not identical to its
interior (Fig. 7.h). There is a significant difference between the arrangement of proteins
and phospholipids and between the two leaflets that form a membrane. On the
membrane's interior, some proteins serve to anchor the membrane to cytoskeleton's
fibers. There are peripheral proteins on the membrane's exterior that bind extracellular
matrix elements. Carbohydrates, attached to lipids or proteins, are also on the plasma
membrane's exterior surface (Figure 7.b). These carbohydrate complexes help the cell
bind required substances in the extracellular fluid. This adds considerably to plasma
membrane's selective nature.
Fig. 7.h. molecular view of the cell membrane. Intrinsic proteins penetrate and bind tightly to the
lipid bilayer, which is made up largely of phospholipids and cholesterol and which typically is between
4 and 10 nanometers (nm; 1 nm = 10 −9 metre) in thickness. Extrinsic proteins are loosely bound to the
hydrophilic (polar) surfaces, which face the watery medium both inside and outside the cell. Some
intrinsic proteins present sugar side chains on the cell's outer surface. 2007 Encyclopædia Britannica,
Inc.

Fig. 7.i. Structural Component of Cellular Membrane

68
 The plasma membrane's exterior surface is not identical to its interior surface.
Recall that plasma membranes are amphiphilic: They have hydrophilic and hydrophobic
regions. This characteristic helps move some materials through the membrane and
hinders the movement of others. Non-polar and lipid-soluble material with a low
molecular weight can easily slip through the membrane's hydrophobic lipid core.
Substances such as the fat-soluble vitamins A, D, E, and K readily pass through the
plasma membranes in the digestive tract and other tissues. Fat-soluble drugs and
hormones also gain easy entry into cells and readily transport themselves into the body‘s
tissues and organs. Oxygen and carbon dioxide molecules have no charge and pass
through membranes by simple diffusion.

Polar substances present problems for the membrane. While some polar
molecules connect easily with the cell's outside, they cannot readily pass through the
plasma membrane's lipid core. Additionally, while small ions could easily slip through the
spaces in the membrane's mosaic, their charge prevents them from doing so. Ions such
as sodium, potassium, calcium, and chloride must have special means of penetrating
plasma membranes. Simple sugars and amino acids also need the help of various
transmembrane proteins (channels) to transport themselves across plasma membranes.

Key Takes of the Permeability of the Lipid Bilayer:

• Hydrophobic (nonpolar) molecules, such as hydrocarbons, can dissolve in the lipid
bilayer and pass through the membrane rapidly.
• Hydrophilic (Polar) molecules, such as sugars, do not cross the membrane easily.

Fig. 7.i. Substances highly impermeable to cross membrane like large uncharged polar molecules
(glucose and fructose), charged molecules and finally ALL IONS. But, Transport proteins are used to
transport ions across membrane.

The Transport Mechanisms

69
1. DIFFUSION
Passive movement of molecules from a region of high concentration to a region of low
concentration.
(Concentration gradient is the difference in concentration between the two regions)
Small, uncharged molecules like O2, CO2 and H2O can move easily through the
membrane.
Works well over short distances. Once molecules enter the cell, the rate of diffusion
slows.
Limits cell size.

Fig. 7.j. Diffusion through a permeable membrane moves a substance from a high concentration area
(extracellular fluid, in this case) down its concentration gradient (into the cytoplasm).

2. OSMOSIS
Diffusion of the solvent across a semi-permeable membrane separating two solutions.
(Diffusion of water)
Water molecules move from a region of high concentration to a region of low
concentration.
Direction depends on the relative concentration of water molecules on either side of
the cell membrane.
Isotonic: Water inside the cell equals the water outside the cell and equal amounts of
water move in and out of the cell.
Hypotonic: Water outside the cell is greater than that inside the cell, water moves into
the cell, may cause cell to burst (lysis)
Hypertonic: Water inside the cell is greater than outside. Water moves out of the cell,
may cause the cell to shrink (plasmolysis)
Fig. 7.k. Movement of water molecules from high concentration to low concentration, through a semi-
permeable membrane.

70
3. FACILITATED TRANSPORT (ALSO KNOWN AS FACILITATED DIFFUSION OR
PASSIVE-MEDIATED TRANSPORT)
Assists with the movement of large molecules like glucose.
Passive movement of a substance into or out of the cell by means of carrier proteins
or channel proteins.
Moves molecules from high to low regions of concentration.
Carrier proteins: Transports noncharged molecules with a specific shape.
Channel proteins: Tunnel shape that transports small charged molecules.
DOES NOT REQUIRE water molecules for other molecules to transfer.

Fig. 7.l. Facilitated diffusion in cell membrane, showing ion channels and carrier proteins.

4. ACTIVE TRANSPORT
The process of moving substances against their concentration gradients Requires
Energy.
Examples:
71
 Kidney cells pump glucose and amino acids out of the urine and back
into the blood.
Intestinal cells pump in nutrients from the gut.
Root cells pump in nutrients from the soil. Gill
cells in fish pump out sodium ions.

Fig. 7.m. Active transport: Requires the use of chemical energy to move substances across a
membrane, against a concentration gradient. Active transport proteins may be uniports, symports, or
antiports.

Active Transport Pump: Sodium-potassium

pump
3 sodium ions inside the cell and 2 potassium ions outside the cell bind to the
pump.
This allows the release of energy from ATP and causes the protein complex to
change shape.
The change in shape allow the Na+ and K+ ions to move across and be
released.
Fig. 7.n. In Primary active transport, energy from the hydrolysis of ATP is used to move ions into or
out of cells against their concentration gradients. The sodium-potassium pump is an important
example.

72
Fig. 7.o. Secondary active transport couples the passive movement of one substance with its
concentration gradient to the movement of another substance against its concentration gradient.
Energy from ATP is used indirectly to establish the concentration gradient that results in the
movement of the first substance.

5. BULK TRANSPORT
1. Endocytosis: The cell membrane folds inward, traps and encloses a small amount
of matter from the extracellular fluid.

73
2. Exocytosis: The reverse of endocytosis: A vesicle from inside the cell moves to the
cell membrane. The vesicle fuses to the membrane and the contents are secreted.

Fig. 7.p. Exocytosis and Endocytosis

Difference between Endocytosis and Exocytosis

Endocytosis refers to Exocytosis refers to the

the transportation of transportation of
macromolecules, large molecules or particles
Definition particles, and polar from the cell to the
substances into the cell outside of the cell
from the external
environment

Process Involved with up taking Involved in removing

nutrients into the cell waste from the cell

Occurs by both Occurs by constitutive

Type phagocytosis and and regulated secretory
pinocytosis pathway

Vesicle Internal vesicles like Secretory vesicles are

phagosomes are formed formed

Cell Wall Not involved Involved

Formation

74
 Engulfing bacteria by Releasing of hormones
Example phagocytes is an out of the cell is an
example example

3 Types of Endocytosis:

Pinocytosis: The intake of a small droplet of extracellular fluid. This occurs in nearly
all cell types.
Phagocytosis: The intake of a large droplet of extracellular fluid. This occurs in
specialized cells.
Receptor-assisted endocytosis: The intake of specific molecules that attach to
special proteins in the cell membrane. These proteins are uniquely
shaped to fit the shape of a specific molecule.

Fig. 7.q. Secondary active transport couples the passive movement of one substance with its
concentration gradient to the movement of another substance against its concentration gradient.
Energy from ATP is used indirectly to establish the concentration gradient that results in the
movement of the first substance.

What’s New

• Visual and Listening Activity:

1. A video link is provided ; ―Cell Transport‖ by Amoeba Sisters (2016),

https://www.youtube.com/watch?v=Ptmlvtei8hw

75
2. Watch and Listen carefully for you to be able to determine and differentiate the types
of transport mechanism in a cell.

3. Make a reaction paper of the video clip.

4. Write it on a long bond paper.

What is cell transport?

It is the movement of substances across the cell membrane either into or out of the cell.
Sometimes things just move through the phospholipid bilayer. Other times, substances
need the assistance of a protein, like a channel protein or some other transmembrane
protein, to cross the cell membrane.

Cell Transport
Cell transport refers to the movement of substances across the cell membrane. Probably
the most important feature of a cell's phospholipid membranes is that they are selectively
permeable. A membrane that is selectively permeable, or semipermeable, has control
over what molecules or ions can enter or leave the cell, as shown in Figure below. This
feature allows a cell to control the transport of materials, as dictated by the cell's
function. The permeability of a membrane is dependent on the organization and
characteristics of the membrane lipids and proteins. In this way, cell membranes help
maintain a state of homeostasis within cells (and tissues, organs, and organ systems) so
that an organism can stay alive and healthy.

A selectively permeable, or semipermeable, membrane allows certain molecules

through, but not others.

Transport Across Membranes

The molecular make-up of the phospholipid bilayer limits the types of molecules that can
pass through it. For example, hydrophobic (water-hating) molecules, such as carbon
dioxide (CO2) and oxygen (O2), can easily pass through the lipid bilayer, but ions such
as calcium (Ca2+) and polar molecules such as water (H2O) cannot. The hydrophobic
interior of the phospholipid bilayer does not allow ions or polar molecules through
because they are hydrophilic, or water loving. In addition, large molecules such as
sugars and proteins are too big to pass through the phospholipid bilayer. Transport
proteins within the membrane allow these molecules to cross the membrane into or out
of the cell. This way, polar molecules avoid contact with the nonpolar interior of the
membrane, and large molecules are moved through large pores.

Every cell is contained within a membrane punctuated with transport proteins that act as
channels or pumps to let in or force out certain molecules. The purpose of the transport
proteins is to protect the cell's internal environment and to keep its balance of salts,
nutrients, and proteins within a range that keeps the cell and the organism alive.

There are four main ways that molecules can pass through a phospholipid membrane.
The first way requires no energy input by the cell and is called simple diffusion. This type
of transport includes passive diffusion and osmosis. No assistance by a transport is
necessary in simple diffusion. Facilitated diffusion, does involve the assistance of
transport proteins. The third way, called active transport, requires that the cell uses
energy to pull in or pump out certain molecules and ions. Active transport involves
proteins known as pumps. The fourth way is through vesicle transport, in which large
molecules are moved across the membrane in bubble-like sacks that are made from
pieces of the membrane. Vesicular transport includes exocytosis and endocytosis.
76
 Homeostasis and Cell Transport
Homeostasis refers to the balance, or equilibrium, within the cell or a body. It is an
organism's ability to keep a constant internal environment. Keeping a stable internal
environment requires constant adjustments as conditions change inside and outside the
cell. The adjusting of systems within a cell is referred to as homeostatic regulation.
Because the internal and external environments of a cell are constantly changing,
adjustments must be made continuously to stay at or near the normal proportions of all
internal substances. This involves continual adjustments in transport of substances
across the cell membrane. Homeostasis is a dynamic equilibrium rather than an
unchanging state. The cellular processes discussed in the cell transport (passive and
active transport) concepts all play an important role in homeostatic regulation.

What Is It

•
Q & A Activity:

1. Why is the transport mechanism vital in a cell?

- Membrane transport is essential for cellular life. As cells proceed through their life
cycle, a vast amount of exchange is necessary to maintain function. Transport
may involve the incorporation of biological molecules and the discharge of waste
products that are necessary for normal function.

2. How are things transported through the membrane?

- Materials move within the cell 's cytosol by diffusion, and certain materials move
through the plasma membrane by diffusion. Diffusion: Diffusion through a
permeable membrane moves a substance from an area of high concentration
(extracellular fluid, in this case) down its concentration gradient (into the
cytoplasm).

3. How will a person know if the transport mechanism in the cell throughout our body is
starting not to work not working?
- when he/she has no longer strenght to release when he/she/'s riding a bike or
when he wants to carry something like things or groceries.

4. What will you compare to the transport mechanism to what we have today?
- Transport mechanisms occurred in shale reservoir include non-Darcy flow,
adsorption/desorption, microscale flow, molecular diffusion, stress-dependent
deformation, and confinement effects.The transport mechanism will determine
how the performance (flux and rejection) of membranes are being modeled in the
water treatment process.

5. If you are to choose what transport mechanism you prefer, what will it be and why?
- Passive because it requires no energy, I won't be tired but I am moving.
convenient.less Hassel.

77
 What’s More

• Crafting Activity:

1. Choose one (1) Transport Mechanism in a cell and make a relatable analogy based
on your experience recently.

2. Illustrate and explain your work on a long bond paper .

3. Write your sketch neatly on a long bond paper.

4. Keep your output in a safe place and submit it on the exact date of submission to be
announced by your teacher.

Passive Transport
Plasma membranes must allow certain substances to enter and leave a cell, and prevent some harmful materials from
entering and some essential materials from leaving. In other words, plasma membranes are selectively permeable—they
allow some substances to pass through, but not others. If they were to lose this selectivity, the cell would no longer be able
to sustain itself, and it would be destroyed. Some cells require larger amounts of specific substances than do other cells;
they must have a way of obtaining these materials from extracellular fluids. This may happen passively, as certain materials
move back and forth, or the cell may have special mechanisms that facilitate transport. Some materials are so important to a
cell that it spends some of its energy, hydrolyzing adenosine triphosphate (ATP), to obtain these materials. Red blood cells
use some of their energy doing just that. All cells spend the majority of their energy to maintain an imbalance of sodium and
potassium ions between the interior and exterior of the cell.

What I Have Learned

• Q & A Activity:

1. Provide the different Transport Mechanisms in a cell with at least 2-3 attributes.
- Simple Diffusion.
- Facilitated Diffusion.
- Osmosis
- Active Transport.
- Endocytosis.
- Exocytosis.

2. How are things transported through the membrane?

- The cell membrane is selectively permeable. It lets some substances pass through
rapidly and some substances pass through more slowly, but prevents other substances
passing through it at all. Some small molecules such as water, oxygen and carbon
dioxide can pass directly through the phospholipids in the cell membrane. Larger
molecules such as glucose require a specific transport protein to facilitate their
movement across the cell membrane. Very large molecules such as proteins are too
big to move through the cell membrane which is said to be impermeable to them. The
78
 type of transport proteins present in a cell membrane determines which substances the
membrane is permeable to.

3. How will a person know if the transport mechanism in the cell throughout our body is
starting not to work not working?
- when he/she has no longer strenght to release when he/she/'s riding a bike or
when he wants to carry something like things or groceries.

4. What will you compare to the transport mechanism to what we have today?
- Transport mechanisms occurred in shale reservoir include non-Darcy flow,
adsorption/desorption, microscale flow, molecular diffusion, stress-dependent
deformation, and confinement effects.The transport mechanism will determine
how the performance (flux and rejection) of membranes are being modeled in the
water treatment process

5. If you are to choose what transport mechanism you prefer, what will it be and why?
- Passive because it requires no energy, I won't be tired but I am moving.
convenient.less Hassel

What I Can Do

• Performance Activity:
1. Choose what you think will be the Transport Mechanism you need to create a story
that reflects what our country is experiencing now.

2. Write your draft on a piece of paper and after you‘re done, transfer it in a long bond
paper .

3. Keep your output in a safe place and submit it on the exact date of submission to be
announced by your teacher.
Assesment

Write the letter of the best answer in the blank.

_1. What is the primary function of carbohydrates attached to the exterior of cell
membranes?
a. identification of the cell
b. flexibility of the membrane
c. strengthening the membrane
d. channels through membrane

79
 _2. Which plasma membrane component can be either found on its surface or
embedded in the membrane structure?
a. protein
b. cholesterol
c. carbohydrate
d. phospholipid

_3. Carbohydrates is found outside the surface of the cell and bounded with? a. lipid or
protein
b. phospholipid
c. glycoprotein
d. glycolipid

_4. Which interacts to hydrophilic and hydrophobic environments? a.

protein
b. cholesterol
c. phospholipid
d. carbohydrate

_5. Which characteristic of a phospholipid contributes to the fluidity of the

membrane?
a. its head
b. cholesterol
c. a saturated fatty acid tail
d. double bonds in the fatty acid tail

_6. What is the primary function of carbohydrates attached to the exterior of cell
membranes?
a. identification of the cell
b. flexibility of the membrane
c. strengthening the membrane
d. channels through membrane
_7. The primary function of the plasma membrane is ….
a. to protect the cell from its surroundings.
b. to provide shape and integrity to the cell.
c. to maintains the cell potential.
d. to be a fluid mosaic model.

_8. Vital for cellular signalling processes that influence tissue and organ
formation
a. membrane markers
b. membrane receptors
c. glycoprotein
d. glycolipid

_9. Cellular Transport Mechanism‘s relation to the Plasma Membrane is…

a. to protect intracellular components from the extracellular environment.
b. to transport materials into or out of the cell
c. to enclose and define the borders of the cell
80
 d. to transmit signals via complex proteins

_10. Cellular Signaling relation to the Plasma Membrane is….

a. to protect intracellular components from the extracellular environment.
b. to enclose and define the borders of the cell
c. to transmit signals via complex proteins
d. to transport materials into or out of the cell

_11. Hydrocarbons dissolve in the lipid bilayer, except for…

a. pass the membrane
b. hydrophobic
c. non polar
d. polar

_12. Which is not a part of the transport mechanisms in cells? a.

facilitated
b. active
c. osmosis
d. excytosis

_13. What is the most direct form of transport mechanisms in cells? a.

passive
b. active
c. osmosis
d. excytosis

_14. Water molecules move from a region of high concentration to a region of low
concentration.
a. facilitated
b. active
c. osmosis
d. diffusion
_15. Moves molecules from high to low regions of concentration with the
transmembrane protein
a. facilitated
b. active
c. osmosis
d. diffusion

_16. All are attributes of exocytosis except for…

a. Involved with up taking nutrients into the cell
b. Secretory vesicles are formed
c. Involved in removing waste from the cell
d. Uninvolved in cell Wall Formation

_17. Water inside the cell equals the water outside the cell and equal
amounts of water move in and out of the cell. a. Osmotic
b. Hypertonic
c. Hypotonic
81
d. Isotonic

_18. Mechanism using ATP

a. facilitated
b. active
c. osmosis
d. excytosis

_19. Engulfment involves…

a. passive
b. active
c. endocytosis
d. excytosis

_20. Waste removal involves….

a. passive
b. active
c. endocytosis
d. excytosis

Structures and Functions of

Lesson
Biological Molecules
- Enzymes

7
What I Need to Know

• Learning Competencies:

1. Describe the components of an enzyme (STEM_BIO11/12-Ii-j-17)

2. Explain oxidation/reduction reactions (STEM_BIO11/12-Ii-j-18)

3. Determine how factors such as pH, temperature, and substrate affect enzyme
activity (STEM_BIO11/12-Ii-j-19)

82
 • Performance Standards:

The learners should be able to construct a cell membrane model from

indigenous or recyclable materials.

• Introduction:

When you were very young and played under the heat of the sun, were
you able to experience sweat dripping in your neck, head and then like some
acid that went in your eyes, it feels burning and stingy right? But don‘t you
worry. Now, we all know that the burning and stingy sensation in our eyes was
due to dust and oils that came in contact with the sweat and to an antimicrobial
enzyme fighting off germs called Lysozyme.

So enzymes are vital for life and serve a wide range of important functions
in the body, such as aiding in fighting germs, digestion, and metabolism.
Some enzymes help break large molecules into smaller pieces that are
more easily absorbed by the body. Other enzymes help bind two molecules
together to produce a new molecule. Enzymes are highly selective catalysts,
meaning that each enzyme only speeds up a specific reaction.

Peeling, bruising, or cutting fruits cause them to release enzymes like

polyphenol oxidase (PPO, phenolase) that, with the presence of oxygen
(oxidation) in the surrounding air, goes into chemical reactions of plant
compounds. These chemical reactions produce brown pigments through the
process of enzymatic browning (Fig. 8.a.)

Oxidation and reduction occur in tandem and it occurred when peeling or

cutting fruits resulting to an enzymatic browning. Because oxidation and
reduction usually occur together, these pairs of reactions are called oxidation
reduction reactions, or redox reactions.

Think of people passing balls back and forth, and the balls are balls of
negativity. So if I'm holding the ball, I'm reduced. If I pass you the ball, you get
reduced, and I become oxidized. The passing of the ball was the reduction-
oxidation reaction.

An oxidation-reduction (redox) reaction is a type of chemical reaction that

involves a transfer of electrons between two species. An oxidation- reduction
reaction is any chemical reaction in which the oxidation number of a molecule,
atom, or ion changes by gaining or losing an electron. A classic example of a
redox reaction is rusting. When rusting happens, oxygen steals electrons
from iron. Oxygen gets reduced while iron gets oxidized.

Fig. 8.a. Enzymatic browning of a sliced apple.

83
 7.1 Transport Mechanisms in Enzymes

What I Know

Write the letter of the best answer in the blank.

_1. Where the reaction is catalysed in an enzyme?

a. Facilitated site
b. Active site
c. Passive site
d. Direct site

_2. Catalyze group transfer reactions; often require coenzymes.

a. Transferases
b. Hydrolases
c. Lyases
d. Isomerases

_3. Lysis of substrate; produce contains double bond.

a. Transferases
b. Hydrolases
c. Lyases
d. Isomerases

_4. Enzymes are described as all of the above except

a. micromolecule
b. macromolecule
c. stereospecific
d. having a defined amino acid sequence

_5. Active forms from one of the inactive enzyme .

84
 a. Apoenzyme
b. Holoenzyme
c. Cofactor
d. Coenzyme

_6. Enzymes described having a typically long amino acid sequence about? a. 100-
400
b. 100-500
c. 100-600
d. 100-700

PRIOR KNOWLEDGE: Definition of Terms

7. Catalyst - a substance that increases the rate of a chemical reaction without itself
undergoing any permanent chemical change.
8. Active Side - In biology, the active site is the region of an enzyme where substrate
molecules bind and undergo a chemical reaction.
9. Enzyme - An enzyme is a substance that acts as a catalyst in living organisms,
regulating the rate at which chemical reactions proceed without itself being altered in
the process.
10. Substrate - the surface or material on or from which an organism lives, grows, or
obtains its nourishment.

What’s In

• REVIEW: Description of the Components of Enzyme

What is an enzyme?

• Enzymes are protein macromolecules.

o They have a defined amino acid sequence, and are typically 100-500
amino acids long.
o They have a defined three-dimensional structure.
• Enzymes are catalysts.
o They act as a catalyst to a chemical or biochemical reaction, with a
defined mechanism.
o They increase the speed of that reaction, typically by 10 6-1014 times faster
than the rate of the uncatalysed reaction.
o They are selective for a single substrate. o They speed up rate of reaction
by lowering the activation energy (Ea).
o They are stereospecific, meaning the reaction produces a single product.

Common mistakes and misconceptions

• Enzymes are "specific." Each type of enzyme typically only reacts with one
(Fig 8.b.), or a couple, of substrates. Some enzymes are more specific than

85
 others and will only accept one particular substrate. Other enzymes can act
on a range of molecules, as long as they contain the type of bond or chemical
group that the enzyme targets.

Fig. 8.b. A substrate entering the active site of the enzyme.

Image modified from "Enzymes: Figure 2," by OpenStax College, Biology, CC BY 3.0.
.

• Enzymes are reusable. Enzymes are not reactants and are not used up
during the reaction. Once an enzyme binds to a substrate and catalyzes the
reaction, the enzyme is released, unchanged, and can be used for another
reaction. This means that for each reaction, there does not need to be a 1:1
ratio between enzyme and substrate molecules.

Nomenclature

Typically add “-ase” to name of substrate

e.g. lactase breaks down lactose (dissacharide of glucose and galactose) Enzymes

based upon the class of organic chemical reaction catalyzed:

1. Oxidoreductase - catalyze redox reactions; dehydrogenases, oxidases,

peroxidases, reductases.
2. Transferases - catalyze group transfer reactions; often require coenzymes.
3. Hydrolases - catalyze hydrolysis reactions.
4. Lyases - lysis of substrate; produce contains double bond.
5. Isomerases - catalyze structural changes; isomerization.
6. Ligases - ligation or joining of two substrates with input of energy, usually from ATP
hydrolysis; often called synthetases or synthases.

ENZYME COMPONENTS (Fig. 8.c.) •

Apoenzyme:
• is an inactive enzyme, activation of the enzyme occurs upon binding of an
organic or inorganic cofactor.
• are enzymes that lack their necessary cofactor(s) for proper functioning
• a Protein

• Holoenzyme: (Fig. 8.d.)

• are the active forms of apoenzymes. (Apoenzyme plus cofactor)
86
 • DNA polymerase and RNA polymerase are examples.

• Cofactor:
• mostly metal ions or small organic molecules, are inorganic and organic
chemicals that assist enzymes during the catalysis of reactions.
• Nonprotein component (e.g. magnesium, zinc)

• Coenzyme:
• are non-protein organic molecules that are mostly derivatives of vitamins
soluble in water by phosphorylation
• Organic cofactor (Eg: NADH, FADH)

Many enzymes can catalyze a reaction only if coenzymes, or cofactors are present.
Fig. 8.c. Parts of an Enzyme

Fig. 8.d. Component of a Holoenzyme

Terminology:
Catalyst
• A substance that speeds up a chemical reaction without being changed

Enzyme
• A biological catalyst (usually a protein)

87
Substrate
• The reactant molecule that an enzyme works on

Active Site
• The part of the enzyme where the substrate binds

Enzyme-substrate complex
• formed when the substrate molecule collides with the active site of its enzyme

Endoenzymes(intracellular) / Exoenzymes (extracellular)

Activation energy
• the minimum energy required to start a chemical reaction

Transition state
• the intermediate stage in a reaction in which the old bonds break and new
bonds are formed

What’s New

• Visual and Listening Activity:

1. A video link is provided ; ―Cofactors | Coenzymes | Holoenzyme | Apoenzyme,

QuickBiochemistry Basics (2020),
https://www.youtube.com/watch?v=LK5HzcAOmyA

2. Watch and Listen carefully to the video and be able to recognize the components of
enzyme.

3. Make a descriptive reaction paper emphasizing the components of the enzyme.

4. Write it neatly on a long bond paper.

cofactor, a component, other than the protein portion, of many enzymes. If the cofactor is
removed from a complete enzyme (holoenzyme), the protein component (apoenzyme)
no longer has catalytic activity. A cofactor that is firmly bound to the apoenzyme and
cannot be removed without denaturing the latter is termed a prosthetic group; most such
groups contain an atom of metal such as copper or iron. A cofactor that is bound loosely
to the apoenzyme and can be readily separated from it is called a coenzyme.
Coenzymes take part in the catalyzed reaction, are modified during the reaction, and
may require another enzyme-catalyzed reaction for restoration to their original state.

What Is It

88
 • Q & A Activity:

1. What are the components of the enzyme that makes it important or vital?
- A large protein enzyme molecule is composed of one or more amino acid chains
called polypeptide chains. The amino acid sequence determines the characteristic
folding patterns of the protein's structure, which is essential to enzyme specificity.

2. How does the component or part of the enzyme contribute to its function?
- Most enzymes are proteins and therefore their function is specific to their
structure. The enzyme binds with the appropriate substrate only in the correct
alignment and orientation to connect the molecules. The resulting enzyme-
substrate complex enables the reaction to occur.

3. What are each of the components attributes? Describe them.

-

(Write your answers on a ½ crosswise intermediate paper.)

What’s More

• Visual and Listening Activity:

1. Watch the video clip ―How Enzymes Work‖, RicochetScience (2015),

https://www.youtube.com/watch?v=UVeoXYJlBtI .

2. The video is explaining the mechanism of an enzymatic activity. But with the image
below, relate what you have learned and try to explain what is happening from #1 -
#5.

3. Draw and label with your best answer on a long coupon bond.

89
 What I Have Learned

• Learning Process Activity:

Write T if the statement is true and F if the statement is false.

1. Substrate binds in the active site. T

2. An enzyme is usually lipid biological catalyst. F
3. The reactant molecule that an enzyme works on is the Substrate. T
4. A Catalyst retards the chemical reaction without being changed F
5. Coenzymes are non-protein organic molecules that are mostly derivatives of vitamins
T
6. Cofactors are small protein organic molecules that assist enzymes during the
catalysis of reactions. T
7. DNA and RNA polymerases are examples of Holoenzyme. F
8. Apoenzyme activation occurs upon binding of an organic or inorganic coenzyme. T
9. Enzymes are reactants and are used up during the reaction. F
10. Once an enzyme binds to a substrate and catalyzes the reaction, the enzyme is
released, unchanged, and can be used for another reaction. T
11. Some enzymes are more specific than others and will only accept one particular
substrate T
12. Enzymes have a defined two-dimensional structure. F
13. Enzyme‘s amino acid sequence are typically 10-500 amino acids long. F
14. Transition state is the intermediate stage in the enzymatic mechanism. F
15. Substrate molecule collides with the active site of its enzyme forms the Enzyme
Substrate complex. F

What I Can Do

• Performance Activity:
1. Life is hard nowadays; you‘re supposed to be able to know how to cook since you‘re
already a Senior High student. You can ask your guardian or parents to help you with
your dish. Choose a recipe that you can easily cook. Only do this at home if you‘re
permitted to do so.

2. Prepare your ingredients and materials for the activity and document everything
using the camera of your phone or just list them down.

3. Write and determine your ingredients that will represent most likely the component of
an enzyme. Describe the process of your activity like what would be the catalyst in your

90
ingredients that sped up the reaction to make the finished product or what your salt
would be represent in the components.

4. After you‘re done baking or cooking with the assistance of your parent or guardian
(photos required if possible), reflect on all of the resources that you‘re able to utilize and
appreciate them by serving your dish (output) first to your family and consume them
together taken with a groufie pic.

5. Document everything from preparing to cooking and serving on a long bond and
secure it until the date of submission that will be announced by the teacher.

7.2 Oxidation/Reduction Reactions What I Know

PRIOR KNOWLEDGE: Definition of Terms

1. Oxidation - The terms oxidation and reduction can be defined in terms of the adding or
removing oxygen to a compound. Oxidation is the gain of oxygen. Reduction is the
loss of oxygen.
2. Reduction - the act of making something smaller or less
3. Oxidants - Any substance that has the ability to oxidize other substance.
4. Reductants - a substance capable of bringing about the reduction of another
substance as it itself is oxidized
5. Reagent - a substance or mixture for use in chemical analysis or other reactions.

What’s In

• REVIEW: Oxidation-Reduction Reactions

An oxidation-reduction (redox) reaction is a type of chemical reaction that involves a

transfer of electrons between two species. An oxidation-reduction reaction is any
chemical reaction in which the oxidation number of a molecule, atom, or ion changes by
gaining or losing an electron. Redox reactions are common and vital to some of the basic
functions of life, including photosynthesis, respiration, combustion, and corrosion or
rusting.

• oxidation-reduction reactions are also called REDOX reactions

• all redox reactions involve the transfer of electrons from one atom to another •
spontaneous redox reactions are generally exothermic, and we can use their
released energy as a source of energy for other applications.

Redox reactions are comprised of two parts, a reduced half and an oxidized half, that
always occur together. The reduced half gains electrons and the oxidation number
decreases, while the oxidized half loses electrons and the oxidation number increases.
Simple ways to remember this include the mnemonic devices OIL RIG, meaning
"oxidation is loss" and "reduction is gain," and LEO says GER, meaning "loss of
e- = oxidation" and "gain of e- = reduced." There is no net change in the number of

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electrons in a redox reaction. Those given off in the oxidation half reaction are taken up
by another species in the reduction half reaction.

A good example of a redox reaction is the thermite reaction, in which iron atoms in
ferric oxide lose (or give up) O atoms to Al atoms, producing Al 2O3.

Fe2O3(s)+2Al(s)→Al2O3(s)+2Fe(l)
What do you mean by oxidation and reduction?

• OXIDATION can be defined as addition of oxygen/electronegative element to a

substance or removal of hydrogen/ electropositive element from a substance.

• REDUCTION can be defined as removal of oxygen/electronegative element from a

substance or addition of hydrogen/ electropositive element to a substance.
*oxidation occurs when an atom’s oxidation
state increases during a reaction

*reduction occurs when an atom’s oxidation

state decreases during a reaction

Development of oxidation and reduction reaction concept _ ___

Reaction of reduction oxidation based on releasing (losing) and gaining of oxygen (capturing).

a. Oxidation reaction is a reaction of gaining (capturing) of oxygen by a substance Ex.

CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)

P4(s) + 5O2(g) → 2P2O5(s)
b. Reduction reaction is a reaction of releasing (losing) of oxygen from an oxide
compound
Ex.

CuO(s) + H2(g) → Cu(s) + H2O(g)

Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g)
What is an oxidizing and reducing agent?
• Oxidizing agent: a reagent which increases the oxidation number of an element of a
given substance. These reagents are called oxidants. It contains the element that is
reduced.
• Reducing agent: a reagent that lowers the oxidation number of a given element.
These reagents are also called reductants. It contains the element that is oxidized.

2 Na(s) + Cl2(g) → 2 Na+Cl–(s)

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Na is oxidized, Cl is reduced
Na is the reducing agent, Cl2 is the oxidizing agent
Terminology:
Reactant
• is a substance or compound added to a system to cause a chemical reaction, or
added to test if a reaction occurs. The terms reactant and reagent are often used
interchangeably—however, a reactant….
Reagent
• is more specifically a substance consumed in the course of a chemical reaction.

What’s New

• Visual and Listening Activity:

1. A video link is provided ; ―Introduction to Oxidation Reduction (Redox) Reactions‖,

Tyler DeWitt (2015), https://www.youtube.com/watch?v=5rtJdjas -mY

2. Watch and Listen carefully to the video and be able to understand REDOX reaction.

3. Make a detailed reaction paper explaining the REDOX reaction. Provide 3 examples.

4. Write it neatly on a long bond paper.

Oxidation‐reduction reactions are some of the most important chemical reactions. Redox
reactions, as they are called, are the energy‐producing reactions in industry as well as in
the body. The core of a redox reaction is the passing of one or more electrons from one
species to another. The species that loses electrons is said to be oxidized, and the
species gaining electrons is reduced. These are old terms, but they are still used today.
Oxidation and reduction occur simultaneously.

Oxidation numbers are assigned to each element in a chemical reaction to help us learn
which element is oxidized and which is reduced. If, in a reaction, the oxidation number of
an element increases (becomes more positive), the element is being oxidized. On the
other hand, if the oxidation number of an element decreases, the element is being
reduced. The changes in oxidation numbers are also used to balance redox equations.
The goal is to keep the total number of electrons lost in the oxidation equal to the total
number gained in the reduction. Clearly, the study of oxidation‐reduction reactions
should begin by learning about oxidation numbers.

What Is It

• Q & A Activity:
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1. What are the components that make up REDOX reaction?
- Redox reactions are comprised of two parts, a reduced half and an oxidized half,
that always occur together. The reduced half gains electrons and the oxidation
number decreases, while the oxidized half loses electrons and the oxidation
number increases. Simple ways to remember this include the mnemonic devices
OIL RIG, meaning "oxidation is loss" and "reduction is gain," and LEO says GER,
meaning "loss of e- = oxidation" and "gain of e- = reduced." There is no net
change in the number of electrons in a redox reaction. Those given off in the
oxidation half reaction are taken up by another species in the reduction half
reaction.

2. Who gains and losses electrons?

- Atoms and chemical species lose or gain electrons when they react in order to gain
stability. Thus, typically, metals (with nearly empty outer shells) lose electrons to non-
metals, thereby forming positive ions. The number of electrons depends on their position
on the Periodic table (in simple terms)
3. When does REDOX reaction happens?
- An oxidation-reduction (redox) reaction is a type of chemical reaction that involves a
transfer of electrons between two species. An oxidation-reduction reaction is any chemical
reaction in which the oxidation number of a molecule, atom, or ion changes by gaining or
losing an electron.
4. Why is REDOX significant to learn?
- Oxidation-reduction (redox) reactions are important because they are the principal
sources of energy on this planet, both natural or biological and artificial. Oxidation
of molecules by removal of hydrogen or combination with oxygen normally
liberates large quantities of energy.

(Write your answers on a ½ crosswise intermediate paper.)

What I Have Learned

• Learning Process Activity:

Write the letter of the best answer in the blank.

_1. A substance consumed in the course of a chemical reaction.

a. Reactant
b. Reagent
c. Reductant
d. Oxidant

_2. Substance added to test if a reaction occurs.

a. Reactant
b. Reagent
c. Reductant
d. Oxidant

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 _3. Contains the element that is oxidized..
a. Reactant
b. Reagent
c. Reductant
d. Oxidant

_4. Contains the element that is reduced.

a. Reactant
b. Reagent
c. Reductant
d. Oxidant

_5. Occurs when an atom‘s oxidation state decreases during a reaction. a.

Oxidation
b. Reduction
c. Reduction-Oxidation Reaction
d. All are correct.

_6. Occurs when an atom‘s oxidation state increases during a reaction. a.

Oxidation
b. Reduction
c. Reduction-Oxidation Reaction
d. All are correct.

_7. Oxidizing agent lowers the oxidation number of a given element. a. True
b. False
_8. True to oxidation-reduction (redox) reaction. Except…
a. OXIDATION can be removal of hydrogen/ electropositive element from a
substance.
b. REDUCTION can be removal of oxygen/electronegative element from a
substance.
c. Spontaneous redox reactions are generally endothermic.
d. All redox reactions involve the transfer of electrons from one atom to another.

7.3 Determining the Factors Affecting Enzyme Activity

What I Know
Place the letters of the best answer inside the box of the factor icon which influences the
activity of the enzyme.

A. Changing this factor outside the enzyme‘s optimum

1. D D range will slow enzyme activity.

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B. Decreasing this factor slows down a reaction

C. This factor at an optimum pH, near neutral causes 2. enzymes to catalyze a reaction most
rapidly. C

D. Increasing this factor will speed up the reaction, as

long as there is substrate available to bind to.
3. B
E. At the saturation point, the reaction will not speed up, no

matter how much of this factor is added.

F. Increasing this factor can cause an enzyme to lose its 4. shape (denature) and
stop working. A

G. Increasing this factor, the greater should be the initial reaction rate
and will last as long as substrate present.

H. This factor‘s graph of the reaction rate will plateau.

What’s In

• REVIEW: Factors Affecting Enzyme Activity

Enzyme activity can be affected by a variety of factors, such as temperature, pH,

concentrations and inhibitors.

Enzymes work best within specific temperature and pH ranges, and sub-optimal
conditions can cause an enzyme to lose its ability to bind to a substrate.

Determnants of the Factors Affecting Enzyme Activites

A. Temperature: Raising temperature generally speeds up a reaction, and lowering

temperature slows down a reaction. However, extreme high temperatures can
cause an enzyme to lose its shape (denature) and stop working. Most enzymes
have an optimum temperature, near normal body temperature at which they
catalyze a reaction most rapidly.

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B. pH (abbr. power of hydrogen or potential for hydrogen ): Each enzyme has an
optimum pH range. Changing the pH outside of this range will slow enzyme
activity. Extreme pH values can cause enzymes to denature. Even small pH
changes can alter the electrical charges on various chemical groups in enzyme
molecules, thereby altering the enzyme‘s ability to bind its substrate and catalyze
a reaction.
Enzymes catalyze a reaction most rapidly at an optimum pH, near neutral.

C. Substrate concentration: Increasing substrate concentration also increases the

rate of reaction to a certain point. Once all of the enzymes have bound, any
substrate increase will have no effect on the rate of reaction, as the available
enzymes will be saturated and working at their maximum rate. At the saturation
point, the reaction will not speed up, no matter how much additional substrate is
added. The graph of the reaction rate will plateau.

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D. Enzyme concentration: Increasing enzyme concentration will speed up the
reaction, as long as there is substrate available to bind to. Once all of the
substrate is bound, the reaction will no longer speed up, since there will be
nothing for additional enzymes to bind to.
The higher the concentration of an enzyme the greater should be the initial
reaction rate. This will last as long as substrate present

E. Enzyme Inhibitors (Inhibition):

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o Competitive inhibitor: A molecule similar in structure to a substrate can
bind to an enzyme‘s active site and compete with substrate

o Noncompetitive inhibitors: attach to the enzyme at an allosteric site,

which is a site other than the active site distort the tertiary protein structure
and alter the shape of the active site.

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o Feedback inhibition: regulates the rate of many metabolic pathways
when an end product of a pathway accumulates and binds to and
inactivates the first enzyme in the metabolic pathway. Product (usually
ultimate product) of a pathway controls the rate of synthesis through
inhibition of an early step (usually the first step). Conserves material and
energy by preventing accumulation of intermediates.

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 What’s New

• Visual and Listening Activity:

1. 2 video links are provided ; “GCSE Biology - How Enzymes Work #11‖ and
―GCSE Biology - Factors that Affect Enzymes #12‖ by Cognito (2018),
Part 1: https://www.youtube.com/watch?v=VNX9UQ08fZ4 Part 2:
https://www.youtube.com/watch?v=qq1foXnvJao

2. Watch and Listen carefully to the video and be able to recognize and relate to each
factors affecting the enzymatic activities.

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 3. Make a detailed reaction paper regarding the video clip yousaw.

4. Write your reaction on a long bond paper.

Enzymes work fastest at their ‘optimum temperature’

In the human body, this optimum temperature is about 37⁰C
Heating to high temperatures (beyond the optimum) will break the bonds that hold the enzyme together and
the active site will lose its shape
The enzyme has been denatured
Effect of temperature on enzyme activity, IGCSE & GCSE Chemistry revision notes

The effect of temperature on enzyme activity

As temperature increases (towards the optimum) the activity of enzymes increases

This is because the molecules have more kinetic energy, move faster and have more successful collisions
with the substrate molecules. This leads to a faster rate of reaction
This means that low temperatures do not denature enzymes, they just make them work more slowly due to
a lack of kinetic energy
Graph showing the effect of temperature on rate of enzyme activity, IGCSE & GCSE Biology revision notes

Graph showing the effect of temperature on the rate of enzyme activity

Factors Affecting Enzyme Action: pH

The optimum pH for most human enzymes is pH 7
Some enzymes that are produced in acidic conditions, such as the stomach, have a lower optimum pH (pH
2)
Some that are produced in alkaline conditions, such as the duodenum, have a higher optimum pH (pH 8 or
9)
If the pH is too far above or too far below the optimum, the bonds that hold the amino acid chain together to
make up the protein can be disrupted or broken
This will change the shape of the active site, so the substrate can no longer fit into it, reducing the rate of
activity
Moving too far away from the optimum pH will cause the enzyme to denature and the reaction it is
catalysing will stop
Effect of pH on enzyme activity, IGCSE & GCSE Biology revision notes

Effect of pH on enzyme activity

Graph showing effect of pH on rate of activity for an enzyme from duodenum, IGCSE & GCSE Biology
revision notes

Graph showing the effect of pH on the rate of activity for an enzyme from the duodenum

Factors Affecting Enzyme Action: Substrate Concentration

The greater the substrate concentration, the greater the enzyme activity and the higher the rate of reaction:
As the number of substrate molecules increases, the likelihood of enzyme-substrate complex formation
increases
If the enzyme concentration remains fixed but the amount of substrate is increased past a certain point,
however, all available active sites eventually become saturated and any further increase in substrate
concentration will not increase the reaction rate
When the active sites of the enzymes are all full, any substrate molecules that are added have nowhere to
bind in order to form an enzyme-substrate complex
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For this reason, in the graph below there is a linear increase in reaction rate as substrate is added, which
then plateaus when all active sites become occupied
At this point (known as the saturation point), the substrate molecules are effectively ‘queuing up’ for an
active site to become available
The effect of substrate concentration on an enzyme-catalysed reaction, downloadable AS & A Level Biology
revision notes

The effect of substrate concentration on the rate of an enzyme-catalysed reaction

What Is It

• Q & A Activity:

1. What are factors involved in the enzymatic activity?

- Enzyme activity can be affected by a variety of factors, such as temperature, pH, and
concentration. Enzymes work best within specific temperature and pH ranges, and sub-
optimal conditions can cause an enzyme to lose its ability to bind to a substrate.
2. How can you determine the effects of each factor of the enzymatic activity?
- Temperature: Raising temperature generally speeds up a reaction, and lowering
temperature slows down a reaction.
- pH: Each enzyme has an optimum pH range.
- Enzyme concentration: Increasing enzyme concentration will speed up the reaction, as
long as there is substrate available to bind to.
3. Select 1 factor that most likely reflects your life as a Senior High student.
- As a senior, you can exercise more freedom. Since most people take easy
classes during their senior year, they have time to hang out with friends after
school and go places. As a senior you will also be able to have an earlier
schedule and come out of school earlier than you ever have.

(Write your answers on a 1 whole intermediate paper.)

What I Have Learned

• Learning Process Activity:

Provide the best answer in the blank.

1. Metabolic pathways_ _ regulates the rate of many metabolic pathways.

2. Allosteric regulation attach to the enzyme at an allosteric site.
3. An Inhibitor can bind to an enzyme‘s active site and compete with
substrate.
4. allosteric siteis a place on an enzyme where a molecule that is not a
substrate may bind.
Enzyme activity can be affected by a variety of factors, such as 5. temperature ,

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 6. pH, 7. enzyme concentration , 8. substrate concentration __ , and 9 . the presence of any
inhibitors or activators.
10. Evidently the graph on a substrate concentration will present a __ A substrate .

What I Can Do

• Performance Activity:
Grow a plant.

A plant can represent an enzyme while your water, soil and sunlight can represent the
substrates. Guess what the inhibitors can represent? Maybe anything that will negatively
affect the plant like not watering it on schedule, not getting enough sunlight and so much
more. We know the byproducts of the plants that are well taken care of, right? Food and
oxygen, or something beneficial to us.

1. Gather a recyclable container like cola bottles, loam soil, fertilizer, etc. Use tools
needed like a small shovel or trowel for transferring the soil inside the container.

3. Decide on a plant you want to easily take care and be beneficial for your household.
Then, secure the seeds or graft of the plant you decided on. Plant it.

4. Document everything for a month (photos included if possible), starting from the first
day of listing down the materials and recording the plant‘s growth in centimeters. Keep a
record notebook for the schedule of submission.

..
Assesment

Write the letter of the best answer in the blank.

_1. Catalyze group transfer reactions; often require coenzymes.

a. Transferases
b. Hydrolases
c. Lyases
d. Isomerases

_2. Where the reaction is catalysed in an enzyme?

a. Facilitated site
b. Active site
c. Passive site
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 d. Direct site

_3. Lysis of substrate; produce contains double bond.

a. Transferases
b. Hydrolases
c. Lyases
d. Isomerases

_4. True to temperature as a factor of enzymatic reaction.

a. This factor at an optimum level, near neutral, causes enzymes to catalyze a
reaction most rapidly.
b. Changing this factor outside the enzyme‘s optimum range will slow enzyme
activity.
c. At the saturation point, the reaction will not speed up, no matter how much of this
factor is added.
d. Increasing this factor can cause an enzyme to lose its shape (denature) and stop
working.

_5. Enzymes are described as all of the above except

a. micromolecule
b. macromolecule
c. stereospecific
d. having a defined amino acid sequence

_6. Active forms from one of the inactive enzyme .

a. Apoenzyme
b. Holoenzyme
c. Cofactor
d. Coenzyme

_7. Enzymes described having a typically long amino acid sequence about? a. 100-
400
b. 100-500
c. 100-600
d. 100-700

_8. Occurs when an atom‘s oxidation state decreases during a reaction. a.

Oxidation
b. Reduction
c. Reduction-Oxidation Reaction
d. All are correct.

_9. Contains the element that is oxidized..

a. Reactant
b. Reagent
c. Reductant
d. Oxidant
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 _10. All the statements are not true to the substrate concentration, except for...
a. This factor at an optimum level, near neutral, causes enzymes to catalyze a
reaction most rapidly.
b. Changing this factor outside the enzyme‘s optimum range will slow enzyme
activity.
c. At the saturation point, the reaction will not speed up, no matter how much of this
factor is added.
d. Increasing this factor can cause an enzyme to lose its shape (denature) and stop
working.

_11. Substance added to test if a reaction occurs.

a. Reactant
b. Reagent
c. Reductant
d. Oxidant

_12. Occurs when an atom‘s oxidation state increases during a reaction. a.

Oxidation
b. Reduction
c. Reduction-Oxidation Reaction
d. All are correct.

_13. Oxidizing agent lowers the oxidation number of a given element. a. True
b. False

_14. True to oxidation-reduction (redox) reaction. Except…

a. OXIDATION can be removal of hydrogen/ electropositive element from a
substance.
b. REDUCTION can be removal of oxygen/electronegative element from a
substance.
c. Spontaneous redox reactions are generally endothermic.
d. All redox reactions involve the transfer of electrons from one atom to another.

_15. A substance consumed in the course of a chemical reaction. a.

Reactant
b. Reagent
c. Reductant
d. Oxidant

_16. Regulates the rate of many metabolic pathways.

a. Feedback inhibition
b. Noncompetitive inhibitors.
c. Competitive inhibitor.
d. Substrate Concentration

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 _17. Can bind to an enzyme‘s active site and compete with substrate.
a. Feedback inhibition
b. Noncompetitive inhibitors.
c. Competitive inhibitor
d. Substrate Concentration

_18. Contains the element that is reduced.

a. Reactant
b. Reagent
c. Reductant
d. Oxidant

_19. Attach to the enzyme at an allosteric site

a. Feedback inhibition
b. Noncompetitive inhibitors
c. Competitive inhibitor
d. Substrate Concentration

_20. True to pH, except for...

a. This factor at an optimum level, near neutral, causes enzymes to catalyze a
reaction most rapidly.
b. Changing this factor outside the enzyme‘s optimum range will slow enzyme
activity.
c. At the saturation point, the reaction will not speed up, no matter how much of this
factor is added.
d. Increasing this factor can cause an enzyme to lose its shape (denature) and stop
working.

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