ANSWERS Worksheets Cell Structure Functions
ANSWERS Worksheets Cell Structure Functions
ANSWERS Worksheets Cell Structure Functions
(Opening image copyright by Sebastian Kaulitzki, 2010. Used under license from Shutterstock.com.)
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3.1 Introduction to Cells
Lesson 3.1: True or False
Name Class Date
Write true if the statement is true or false if the statement is false.
FALSE 1. All organisms are made of more than one cell.
FALSE 2. Early microscopes created by Leeuwenhoek were almost as strong as modern light microscopes.
TRUE 3. Proteins are made on ribosomes.
FALSE 4. Prokaryotic cells have a nucleus.
TRUE 5. The plasma membrane forms the physical boundary between the cell and its environment.
TRUE 6. For cells, a smaller size is more efficient.
FALSE 7. Compared to eukaryotic cells, prokaryotic cells are very complex.
TRUE 8. Organelles are located within the cytoplasm.
FALSE 9. Viruses are similar to prokaryotic cells.
TRUE 10. All cells have a plasma membrane, cytoplasm, and ribosomes.
FALSE 11. DNA is located in the nucleus of prokaryotic cells.
TRUE 12. Organelles allow eukaryotic cells to carry out more functions than prokaryotic cells.
TRUE 13. Viruses are considered living organisms.
TRUE 14. Most cells are about the size of the period at the end of this sentence.
TRUE 15. Observation of cork helped in the discovery of cells.
Lesson 3.1: Critical Reading
Name Class Date
Read these passages from the text and answer the questions that follow.
Two Types of Cells
There is another basic cell structure that is present in many but not all living cells: the nucleus. The nucleus of a
cell is a structure in the cytoplasm that is surrounded by a membrane (the nuclear membrane) and contains DNA.
Based on whether they have a nucleus, there are two basic types of cells: prokaryotic cells and eukaryotic cells.
Prokaryotic Cells
Prokaryotic cells are cells without a nucleus. The DNA in prokaryotic cells is in the cytoplasm rather than
enclosed within a nuclear membrane. Prokaryotic cells are found in single-celled organisms, such as bacteria.
Organisms with prokaryotic cells are called prokaryotes. They were the first type of organisms to evolve and are
still the most common organisms today.
Eukaryotic Cells
Eukaryotic cells are cells that contain a nucleus. Eukaryotic cells are usually larger than prokaryotic cells, and
they are found mainly in multicellular organisms. Organisms with eukaryotic cells are called eukaryotes, and they
range from fungi to people. Eukaryotic cells also contain other organelles besides the nucleus. An organelle is a
structure within the cytoplasm that performs a specific job in the cell. Organelles called mitochondria, for
example, provide energy to the cell, and organelles called vacuoles store substances in the cell. Organelles allow
eukaryotic cells to carry out more functions than prokaryotic cells can.
Viruses: Prokaryotes or Eukaryotes?
Viruses are tiny particles that may cause disease. Human diseases caused by viruses include the common cold
and flu. Do you think viruses are prokaryotes or eukaryotes? The answer may surprise you. Viruses are not cells at
all, so they are neither prokaryotes nor eukaryotes.
Viruses contain DNA but not much else. They lack the other parts shared by all cells, including a plasma
membrane, cytoplasm, and ribosomes. Therefore, viruses are not cells, but are they alive? All living things not
only have cells; they are also capable of reproduction. Viruses cannot reproduce by themselves. Instead, they
infect living hosts, and use the hosts’ cells to make copies of their own DNA. For these reasons, most scientists do
not consider viruses to be living things.
Questions
1. What is one main difference between prokaryotic and eukaryotic cells?
The main difference between prokaryotic and eukaryotic cell is that prokaryotic cell are cells that does not have
nucleus and thery are found in single-celled organisms such as bacteria while in the eukaryotic cells contains
nucleus and organisms with eukaryotic cells are called eukaryotes and they range from fungi to people.
3. What is an organelle? Give three examples. (Hint: See the Eukaryotic Cell figure in the FlexBook.)
An organelle is a tiny cellular structure that performs specific functions within a cell. Organelles are embedded
within the cytoplasm of eukaryotic and prokaryotic cells. Organelles are structures within a cell that perform specific
functions like controlling cell growth and producing energy. Examples of organelles found in eukaryotic cells
include: the endoplasmic reticulum (smooth and rough ER), the Golgi complex, lysosomes, mitochondria,
peroxisomes, and ribosomes.
4. Describe the nucleus. What can be found inside the nucleus?
The nucleus is a highly specialized organelle that serves as the information processing and administrative center
of the cell. The nucleus is a membrane-bound organelle that contains genetic material or the DNA of eukaryotic
organisms. It also serves to maintain the integrity of the cell by facilitating transcription and replication
processes. It's the largest organelle inside the cell taking up about a tenth of the entire cell volume. The nucleus
houses the cell's genetic material, or DNA and is also the site of synthesis for ribosomes, the cellular machines
that assemble proteins. Inside the nucleus, chromatin which is the DNA wrapped around proteins is stored in a
gel-like substance called nucleoplasm.
Viruses are not living things. Viruses are complicated assemblies of molecules, including proteins, nucleic acids,
lipids, and carbohydrates, but on their own they can do nothing until they enter a living cell. Without cells, viruses
would not be able to multiply. Therefore, viruses are not living things. Viruses are not living things. They lack the
other parts shared by all cells. They are not cells and cannot reproduce by themeselves instead, they infect living
hosts and use the hosts' cells to make copies of their own DNA.
Lesson 3.1: Multiple Choice
Name Class Date
Circle the letter of the correct choice.
The phospholipid bilayer consists of two layers of phospholipids (left), with a hydrophobic, or water-hating,
interior and a hydrophilic, or water-loving, exterior. A single phospholipid molecule is depicted on the right.
(Image courtesy of CK-12 Foundation and under the Creative Commons license CC-BY-NC-SA 3.0.)
Other Molecules in the Plasma Membrane
The plasma membrane also contains other molecules, primarily other lipids and proteins. The green molecules in
the figure above, for example, are the lipid cholesterol. Molecules of cholesterol help the plasma membrane keep
its shape. Many of the proteins in the plasma membrane assist other substances in crossing the membrane.
Extensions of the Plasma Membrane
The plasma membrane may have extensions, such as whip-like flagella or brush-like cilia. In single-celled
organisms, the membrane extensions may help the organisms move. In multicellular organisms, the exten- sions
have other functions. For example, the cilia on human lung cells sweep foreign particles and mucus toward the
mouth and nose.
Questions
1. What is the plasma membrane?
Stated from the given handouts about plasma membrane, it forms a barrier between the cytoplasm inside the cell and
the environment outside the cell. It protects and supports the cell and also controls everything that enters and leaves
the cell. It allows only certain substances to pass through, while keeping others in or out. The ability to allow only
certain molecules in or out of the cell is referred to as selective permeability or semipermeability.
2. What is the meaning of semipermeability?
Allowing passage of certain, especially small, molecules or ions but acting as a barrier to others. Used of
biological and synthetic membranes. Semipermeability means partially permeable which gives the plasma
membrane the ability to let good molecules in and bad ones out of the cytoplasm.
4. What are some of the “other” molecules in the plasma membrane? Describe their function.
The plasma membrane also contains other molecules, primarily other lipids and proteins. For example, are the
lipid cholesterol. Molecules of cholesterol help the plasma membrane keep its shape. Many of the proteins in the
plasma membrane assist other substances in crossing the membrane.
Cilia and flagella are tube-like appendages which allow for motion in eukaryotic cells. The motion of the cilia or
flagellum moves the liquid outside the cell and if the cell is not anchored, it can swim. A commonly recognized
example is the "tail" on a sperm cell, which is actually a flagellum. Cilia and flagella are motile cellular appendages
found in most microorganisms and animals, but not in higher plants. In multicellular organisms, cilia function to
move a cell or group of cells or to help transport fluid or materials past them.
Lesson 3.2: Multiple Choice
Name Class Date
Circle the letter of the correct choice.
• Channel proteins form pores, or tiny holes, in the membrane. This allows water molecules and small ions to
pass through the membrane without coming into contact with the hydrophobic tails of the lipid molecules in
the interior of the membrane.
• Carrier proteins bind with specific ions or molecules, and in doing so, they change shape. As carrier
proteins change shape, they carry the ions or molecules across the membrane.
Questions
1. Explain why passive transport does not require energy.
No energy is needed because the substances are moving from an area where they have a higher concentration to
an area where they have a lower concentration.
Diffusion is the driving force behind the movement of many substances across the cell membrane. Facilitated
diffusion is where molecules cannot directly diffuse across the membrane pass through special protein channels.
Diffusion is the movement of a substance across a membrane, due to a difference in concentration, without any help
from other molecules. The substance simply moves from the side of the membrane where it is more concentrated to
the side where it is less concentrated. The help comes from special proteins in the membrane known as transport
proteins. Diffusion with the help of transport proteins is called facilitated diffusion.
3. Describe how simple diffusion proceeds. What kind of molecules can move across the membrane by simple
diffusion?
Substances that can squeeze between the lipid molecules in the plasma membrane by simple diffusion are
generally very small, hydrophobic molecules,such as molecules of oxygen and carbon dioxide.
5. What are the two types of transport proteins? Describe how they function.
There are several types of transport proteins, including channel proteins and carrier proteins.
Channel proteins form pores, or tiny holes, in the membrane. This allows water molecules and small ions to pass
through the membrane without coming into contact with the hydrophobic tails of the lipid molecules in the interior
of the membrane.
Carrier proteins bind with specific ions or molecules, and in doing so, they change shape. As carrier proteins change
shape, they carry the ions or molecules across the membrane.
Lesson 3.3: Multiple Choice
Name Class Date
Circle the letter of the correct choice.
1. Controlling what enters and leaves the cell in an important function of the
(a) nucleus.
(b) vesicle.
(c) plasma membrane.
(d) Golgi apparatus.
2. During diffusion, substances move from an area of concentration to an area of
concentration.
(a) higher, lower
(b) lower, higher
(c) higher, equal
(d) lower, equal
3. A channel protein does which of the following?
(a) Carries ions or molecules across the membrane.
(b) Forms tiny holes in the membrane.
(c) Changes shape as it transports molecules.
(d) all of the above
4. The sodium-potassium pump
(a) uses energy to move sodium ions out of the cell and potassium ions into the cell.
(b) uses energy to move potassium ions out of the cell and sodium ions into the cell.
(c) moves sodium ions out of the cell and potassium ions into the cell without using energy.
(d) moves potassium ions out of the cell and sodium ions into the cell without using energy.
5. Osmosis
(a) is the diffusion of water.
(b) is the diffusion of water and other small molecules.
(c) is the diffusion of water and small ions.
(d) is the diffusion of small molecules and ions.
6. Types of passive transport include which of the following? (1) simple diffusion, (2) osmosis, (3) facilitated
diffusion, (4) active transport, and (5) vesicle transport.
(a) 1 and 2
(b) 1, 2, and 3
(c) 4 and 5
(d) 1, 2, 3, 4, and 5
7. Endocytosis and exocytosis
(a) are both a type of vesicle transport.
(b) move very large molecules either in or out of the cell.
(c) are both a form of active transport.
(d) all of the above
8. Which of the following needs energy? (1) passive transport, (2) active transport, (3) exocytosis, and
(4) osmosis.
(a) 1 only
(b) 2 only
(c) 2 and 3
(d) 2, 3, and 4
Lesson 3.3: Vocabulary I
Name Class Date
Match the vocabulary word with the proper definition.
Definitions
H 1. transport across a membrane without any additional energy requirement
G 2. the diffusion of water
D 3. type of vesicle transport that moves a substance into the cell
E 4. type of vesicle transport that moves a substance out of the cell
J 5. special proteins in the membrane that aid diffusion
B 6. membrane protein that forms a small hole that allows ions to pass through
I 7. an active transport protein
F 8. diffusion with the help of transport proteins
C 9. the movement of a substance across a membrane without any help from other molecules
K 10. the transport of very large molecules, such as proteins
A 11. transport across a membrane in which energy is required
Terms
a. active transport
b. channel protein
c. diffusion
d. endocytosis
e. exocytosis
f. facilitated diffusion
g. osmosis
h. passive transport
i. sodium-potassium pump
j. transport protein
k. vesicle transport
Lesson 3.3: Vocabulary II
Name Class Date
Fill in the blank with the appropriate term.
1. By moving substances into and out of cells, HOMEOSTASIS , the process of keeping stable conditions
inside a cell, is maintained.
2. A CARRIER protein changes shape as it carries ions or molecules across the membrane.
3. Exocytosis is the type of VESICLE transport that moves a substance out of the cell.
4. PASSIVE transport is movement across the plasma membrane that does not require an input of
energy.
5. The sodium-potassium PUMP is involved in the active-transport of ions.
6. Facilitated diffusion needs the help of TRANSPORT proteins
7. CONCENTRATION refers to the number of particles of a substance per unit of volume.
8. ENDOCYTOSIS is the type of vesicle transport that moves a substance into the cell.
9. Energy for active transport is supplied by molecules of ATP .
10. OSMOSIS is the diffusion of water.
11. During active transport, a substance is moving from an area of LOW concentration to
an area of HIGH concentration.
12. Moving molecules in and out of the cell is an important role of the PLASMA MEMBRANE .
Lesson 3.3: Critical Writing
Name Class Date
Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete
sentences.
Discuss passive and active transport. Describe the main differences between these two types of transport, and
provide examples of each type.