As-Level Biology Notes: By: Bianca Himawan
As-Level Biology Notes: By: Bianca Himawan
As-Level Biology Notes: By: Bianca Himawan
TABLE OF CONTENTS:
CHAPTER 1 Cell Structure Page 1
CHAPTER 2 Biological Molecules Page 5
CHAPTER 3 Enzymes Page 13
CHAPTER 4 Cell Membrane and Transport Page 17
CHAPTER 5 The Mitotic Cell Cycle Page 22
CHAPTER 6 Nucleic Acids and Protein Synthesis Page 27
CHAPTER 7 Transport in Plants Page 31
CHAPTER 8 Transport in Mammals Page 40
CHAPTER 9 Gas Exchange and Smoking Page 49
CHAPTER 10 Infectious Diseases Page 53
CHAPTER 11 Immunity Page 59
AS-LEVEL BIOLOGY NOTES BIANCA HIMAWAN
PRESENCE OF ORGANELLES
animals both plants
magnification the number of times an image is greater than the actual size of
the object
resolution the ability to distinguish between two objects very close together;
the higher the resolution, the greater the detail
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prokaryotes eukaryotes
DNA circular and free in cytoplasm DNA not circular, inside nucleus
no ER ER present
VIRUSES
1. parasitic, needs a host
2. do not have cell structures, consists of:
– self replicating molecule of DNA/RNA acting as genetic code
– protective capsid (protein coat) called capsomere
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CARBOHYDRATES
monosaccharides
1. (CH2O)n
disaccharides
1. made up of two monosaccharides with glycosidic bonds
2. types:
– maltose = glucose + glucose
– sucrose = glucose + fructose
– lactose = glucose + galactose
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polysaccharides
1. polymers of monosaccharides
2. uses for converting glucose to polysaccharides:
– to store as appropriate form for main energy source
– glucose accumulation in cells will dissolve and make cell contents too
concentrated, affecting osmosis
– glucose is reactive and will interfere with normal cell chemistry
3. starch in plants
4. glycogen in animals
5. glucose made available by enzyme-controlled action
cellulose
– has structural role
– mechanically strong
– polymer of ß-glucose
– why cellulose is strong:
1. one ß-glucose turned upside down for glycosidic bond
2. that arrangement results in strong molecules, since H atoms are weakly
attached to oxygen molecules
3. abundance in hydrogen bonds
4. cellulose molecules become tightly cross-linked to form microfibrils
5. microfibrils held together in bundles to form fibers by hydrogen bonds
6. cell wall has several fiber layers running in different directions
7. other molecules help cross-link the cellulose fibers and form glue-like
matrix
8. very high tensile strength, can withstand pressure
starch
– amylose + amylopectin mixture
amylose = α-glucose, 1,4-glycosidic bonds
amylopectin = 1,4 α-glucose, shorter than amylose, with 1,6 branches
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glycogen
– 1,4 α-glucose
– 1,6 branches
– more branches than amylopectin
LIPIDS
– fats are solid, oils are liquid (at room temperature)
– lipids are esters of fatty acids and alcohol
fatty acids
1. contain acidic group -COOH
2. have long hydrocarbon tails attached to the head
3. tails with C=C are unsaturated with a ‘kink’, melts more easily
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triglycerides
1. most common lipids
2. 3 fatty acids + 1 glycerol
3. insoluble in water, soluble in ether, chloroform
4. hydrophobic tails
5. roles of triglycerides:
– energy reserves, richer in carbon-hydrogen bonds
– insulator against heat loss
– provides buoyancy in blubber
– metabolic source of water
phospholipids
1. hydrophobic tail, hydrophilic head
2. the 3 fatty acids replaced by polar phosphate group
3. has 2 tails
4. hydrophobic tails form a layer that is impermeable to hydrophilic substances
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PROTEINS
1. all enzymes are proteins
2. act as receptor/signaling proteins in cell membrane
3. hormones (insulin, glucagon)
4. haemoglobin/myoglobin
5. antibodies
6. collagen
7. keratin
8. actin/myosin for muscle contractions
9. storage products (casein in milk; ovalbumin in egg)
amino acids
1. all have central carbon atom bonded to amine group (-NH2), and -COOH, and hydrogen,
and R group
2. R groups differ with each type of amino acid
peptide bond
condensation
O=C–NH <—————————- amino acids
primary structure
1. peptide bond
2. sequence of amino acids is a polypeptide
3. amino acids linked into a long chain
secondary structure
1. hydrogen bonds
2. structure of a protein molecule resulting from the regular coiling/folding of amino acid
chain (α-helix, ß-pleated sheet)
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tertiary structure
1. disulfide bonds
2. compact structure of a protein molecule resulting from the three-dimensional coiling of
already-folded chain of amino acids
quaternary structure
1. hydrogen bonds
2. e.g. haemoglobin
3. three-dimensional arrangement of two or more polypeptides, or of a polypeptide and a
non-protein component such as a haem in a protein molecule
globular fibrous
haemoglobin
1. oxygen-carrying pigment found in RBC
2. globular protein
3. 4 polypeptide chains, 4 haem groups
4. α and ß globin
5. spherical
6. hydrophobic inwards, hydrophilic outwards, to maintain solubility
7. 4 O2 molecules, 8 O atoms
8. oxyhemoglobin is red, deoxyhaemoglobin is purple
9. sickle cell anaemia:
– one amino acid, glu, is replaced with val, results in less soluble haemoglobin
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collagen
1. fibrous protein
2. insoluble
3. structural protein
4. why it is strong:
– each molecule consists of 3 polypeptide chains, each in helix shape, wound around
each other to form 3-stranded rope called triple helix
– it is held together by hydrogen bonds and covalent bonds
– glycine is found in the strand, small size allows strands to lie closer together to form
tight coil
– each 3-stranded molecule interacts with other molecules running parallel to it
– there are covalent bonds between R groups of amino acids lying next to each other
– cross-links hold many molecules side by side to form fibrils
– the ends of parallel molecules are staggered
– many fibrils lie alongside each other to form strong bundles called fibers
– flexible with great tensile strength
– fibers line up according to forces they must withstand
– in tendons, they line up in parallel bundles in direction of tension
– in skin, they form layers with fibers running in different directions in different layers
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WATER
1. major component of cells
2. provides environment for water organisms
3. liquid because of hydrogen bonds
4. liquidity provides medium for molecules/ions
5. causes non-polar molecules to group together
6. high cohesion and surface tension, allows organisms to live on its surface
7. acts as a reagent inside cells (hydrolysis; photosynthesis as source of hydrogen)
8. hydrogen bonding makes molecules more difficult to separate
9. excellent solvent for ions/polar molecules
10. as a transport medium:
– in blood
– lymph
– digestive system
– vascular tissue
11. high specific heat capacity
– amount of heat needed to raise the temperature of 1kg by 1ºC
12. high latent heat of vaporization
– measure of heat energy needed to vaporize a liquid (change from liquid to gas)
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CHAPTER 3 ENZYMES
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EFFECT OF ENZYMES
– reduce activation energy
COURSE OF REACTION
vol O2
time
1. when enzyme and substrate are first mixed, there is still an abundance of substrates
2. as more substrate turns to product, there are fewer substrate left to bind with enzyme
3. the graph steepest at start (initial rate of reaction) because action fastest at beginning
4. no more substrate is left after some time, only product, curve flattens
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INHIBITORS
– affect the tertiary structure of an enzyme
competitive inhibitor
– affects active site, binds to it and prevents proper substrate from doing so
– similar in shape to substrate, complementary to active site
incompetitve inhibitor
– affects parts of enzyme other than active site
– deforms active site
– enzyme cannot bind to substrate without specific active site shape
MICHAELIS-MENTEN CONSTANT
– Km = 1/2 Vmax
– significance:
1. helps how reaction in proposed pathway proceeds
2. compare quantitatively enzyme preference for different substrates
3. design better catalysts
4. compare performance of enzymes from other organisms
5. calculation can be used in other fields (e.g. antibody-antigen binding)
6. proportion of active sites occupied can be calculated for any substrate
concentration
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IMMOBILIZING ENZYMES
1. for commercial applications
2. keeps low cost
3. can be immobilized by alginate beads (for lactose)
4. produce lactose-free milk
5. keep/reuse enzymes
6. more tolerant to temperature/pH changes (held firmly in shape)
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PHOSPHOLIPID
unsaturated double bonds form ‘kink’, keeps membrane fluid in low temperatures
ROLES OF COMPONENTS
name function
phospholipid forms the bilayer; tails non-polar and makes the entrances of
polar molecules/ions difficult; can become signaling molecules to
activate other molecules like enzyme; can be hydrolyzed to form
aqueous glycerol-related molecules that diffuse through
cytoplasm and bind to receptors
cholesterol small, with hydrophobic/hydrophilic parts to fit between
phospholipids; absent in prokaryotes; increases fluidity at low
temperatures; prevents rigidity/close packing of phospholipids;
interaction with phospholipids helps stabilize cells at higher
temperatures; important for mechanical stability of the membrane
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glycolipid/glycoprotein project like antennae into watery fluid outside; receptor molecules
that bind with particular substances at cell surface; unique for
each substance; signaling receptors; endocytosis; act as antigens
for cell recognition
protein medium for transport in and out of cell by facilitated diffusion;
channel protein, carrier protein; enzyme
CELL SIGNALING
– control and coordinate the bodies of living organisms
– to respond appropriately to their environments
– signaling pathway:
1. receive stimulus
2. transmission of message to receptor
3. conversion of message (transduction)
4. transmission to target (effector)
5. response formed
– includes both electrical and chemical events and interactions (hormones/neurotransmitter)
– signaling molecules mostly water-soluble
– hydrophilic signaling molecules can diffuse directly across membrane and bind to
receptors in cytoplasm/nucleus
– receptor has specific shape with its signaling molecule
– signaling pathway (with second messenger):
1. signal arrives at protein receptor
2. transduction to inside cell, or G protein
3. G protein activates enzyme
4. enzyme makes second messenger (small, soluble, amplifies signal)
5. second messenger activates an enzyme, which further activates others, increasing
amplification (this is called signaling cascade)
6. response formed
– ways in which receptor can alter cell activity:
1. opening ion channel, changes membrane potential
2. acting as membrane-bound enzyme
3. acting as intracellular receptor inside cell
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MOVEMENT OF SUBSTANCES
diffusion
– the net movement of molecules or ions from a region of higher concentration to a region of
lower concentration down a gradient, as the result of random particle movement
– factors affecting the rate of diffusion
1. steepness of concentration gradient
2. temperature
3. surface area
4. size/polarity of molecules (nature of molecule)
facilitated diffusion
– the diffusion of a substance through transport proteins in a cell membrane; the proteins
provide hydrophilic areas that allow the molecules or ions to pass through the membrane
that would otherwise be permeable
– channel proteins
1. water-filled pores
2. allow charged substances (ions) to diffuse
3. ‘gated’; inner part can open/close for control
4. repolarization in nerve cell surface membranes, one type of channel allows
entrance of sodium ions, another the exit of potassium ions during recovery phase
5. fixed shape
– carrier proteins
1. can flip between two shapes; binding cute can be open to one side of membrane
to another
2. direction depends on concentration in/out of membrane
3. cystic fibrosis caused by defect in carrier proteins of lungs, prevents movement of
chloride ions
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osmosis
– diffusion involving water only, through partially-permeable membrane
– solute + solvent = solution
– water potential (tendency of water to move out of solution)
1. how much water in solution compared to solutes
2. how much pressure applied
– solute and pressure potential
1. (solute) contribution of concentration of solution to water potential; the
more solute, the lower the tendency of water moving out
2. (pressure) contribution of pressure to water potential; the higher the
pressure, the greater the tendency of water moving out
– in animal cells
1. water potential too high, cell bursts
2. too low, it shrinks
– in plant cells
1. too high, cell wall pushes against expanding protoplast, builds rapid
pressure; turns turgid
2. too low, protoplast shrinks away from cell wall; plasmolysis
active transport
– against concentration gradient, high to low regions of concentration
– movement of molecules/ions
– requires ATP, to change shape of carrier protein
– through transport protein
1. Na+ — K+ pump
2. 3 Na+ ions out, 2 K+ ions in per ATP molecule
– significance:
1. important in kidney reabsorption
2. absorption of digestion products in gut
3. load sugar from photosynthesizing leaf cells to phloem tissue for transport
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bulk transport
– transport of large quantities of products
– endocytosis into cells; exocytosis out of cells
– requires ATP, as it is a form of active transport
– endocytosis (engulfing material by cell membrane to form small sac ‘endocytic vacuole’)
1. phagocytosis: ‘cell eating’; bulk uptake of solid material; by phagocytes; forms
phagocytic vacuole
2. pinocytosis: ‘cell drinking’; bulk uptake of liquid material; vacuoles formed often
small, called micropinocytosis
– exocytosis: removal of materials from cells; reverse of endocytosis; secretion
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CHROMOSOMES
structure
1. made of two identical structures called chromatids
2. chromatids joined together by a centromere
3. each chromatid contains one DNA molecule
4. DNA made up of a series of genes
5. genes are coding for one polypeptide that is involved in a specific function of organism
6. also made of chromatin
– euchromatin: loosely coiled
– heterochromatin: tightly coiled
7. chromatin is a combination of DNA and protein
MITOSIS
the cell cycle
G2 M
S cytokinesis
G1
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phase description
G1 cells make RNA, enzymes, other proteins needed for growth; at the end of
G1, cell becomes committed to dividing or not dividing
S a signal may be received if the cell has to divide again; DNA replicates so
that each chromosome consists of two identical chromatids
G2 cell continues to grow and new DNA is checked and any errors are repaired;
preparations are made to begin process of division
M nuclear division; prophase, metaphase, anaphase, telophase
cytokinesis animal cell division involves constriction of the cytoplasm between the two
new nuclei; plant cell involves the formation of a new cell wall between two
new nuclei
mitosis
– prophase
(early prophase)
1. centrosomes replicate just before prophase
2. chromosomes start to appear as the chromatin coils up, becoming shorter and thicker
3. there are centromeres with attached kinetochore
4. nuclear envelope still intact, nucleolus still visible
(late prophase)
1. centrosomes move to opposite ends of nucleus
2. chromosomes are seen to consist of two identical chromatids
3. nucleolus and envelope disappears (becomes small vesicles invisible to light microscope)
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– metaphase
– anaphase
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– telophase
1. nucleus reforms
2. remains of spindle breaks down
3. centrosome will replicate during interphase
4. nuclear envelope reforming
5. chromatids have reached the poles of the spindle; they then uncoil again
6. cytokinesis will occur to split the cell by constriction from edges of cell
significance of mitosis
1. growth
2. replacement of cells and repair of tissues
3. asexual reproduction
4. immune response (reproduction of B/T lymphocytes)
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TELOMERES
– the ends of chromosomes are ‘sealed’ by telomeres
– significance
1. permit continued replication
2. prevent loss of genes
3. protect ends of chromosomes from being degraded
4. prevent ends of chromosomes from attaching to each other
STEM CELLS
– cell that can divide an unlimited number of times by mitosis
– each new cell has the potential to remain a stem cell or develop into a specialized cell
– potency: extent of power that a stem cell has to produce different cell types
1. totipotent: can develop to any type of cell (e.g. zygote)
2. pluripotent: lose ability to produce placenta cells but can produce all cells to
develop into embryo
3. multipotent: can only produce few types of cells; in bone marrow (in adults)
– for growth and repair
– stem cell therapy
1. introduction of new adult stem cells into damaged tissue to treat disease/injury
2. bone marrow transplantation
CANCER
– result of uncontrolled mitosis; cancerous cells divide repeatedly to form tumor
– tumor: irregular mass of cells; shows abnormal changes in shape
– mutation: when changes occur to genes that control cell division
– oncogene: mutated gene that causes cancer
– carcinogen: any agent that causes cancer
– benign tumors: do not cause cancer
– malignant tumor: causes cancer
1. interfere with the normal functioning area where they grow
2. cells can break off to blood/lymphatic system to other parts of body to form
secondary growth; metasis
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nucleotides
– nucleotides make up DNA/RNA; polynucleotides
– made up of 3 smaller components:
1. nitrogen-containing base
2. pentose sugar
3. phosphate group
– 5 types:
1. adenine
2. thymine (DNA only)
3. guanine
4. cytosine
5. uracil (RNA only)
– purine vs. pyrimidine
1. purine (PURE As Gold): adenine and guanine
– has 2 rings
2. pyrimidine: thymine, cytosine, uracil
– has only 1 ring
P
BASE
SUGAR
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ATP
– structure similar to nucleotide
– adenosine triphosphate (3 phosphate groups); diphosphate; monophosphate
– adenine + ribose = adenosine
polynucleotides
– DNA/RNA
– made up of many nucleotides linked together in long chain
– takes place inside nucleus, during interphase of cell cycle
– formed of alternating sugars and phosphates linked together with bases to one side
– covalent sugar-phosphate bonds link 5-carbon of one sugar to 3-carbon of the next
– have 3’ and 5’ ends
– DNA molecules
1. made of 2 polynucleotide strands lying side by side, running opposite ways
2. antiparallel
3. two strands held together by hydrogen bonds between bases
4. must be purine + pyrimidine
5. complementary base pairing (AT 2 bonds; GC 3 bonds)
6. double helix structure
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DNA REPLICATION
semi-conservative replication
– half of original molecule is kept (conserved) in each of the new molecules
– original DNA made up of heavy isotope of nitrogen called 15N; after replication it contains
both 15N and a lighter nitrogen isotope, called 14N; after further replication, some DNA
contains 14N only
– mechanism:
1. the DNA double helix unwinds as the hydrogen bonds between bases break
2. in the nucleus, there are nucleotides to which two extra phosphates have been
added
3. the extra phosphates activate the nucleotides, enabling them to take part in
the following reactions
4. each of the bases of the activated nucleotides pairs up with its complementary
base on each of the old DNA strands
5. DNA polymerase links the sugar and innermost phosphate groups of next-door
nucleotides together
6. the two extra phosphates are broken off and released into the nucleus
7. DNA polymerase will only link an incoming nucleotide to the growing new chain if it
is complementary to the base on the old strand
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triplet code
– a sequence of three bases
– makes one amino acid
– complementary strand called anti-sense strand
– read in direction of lower strand
transcription
1. in nucleus, part of DNA unwinds as the hydrogen bonds between bases break
2. free activated RNA nucleotides pair up with the exposed bases of one strand only
3. as RNA nucleotides pair up with complementary ones, their sugar-phosphate groups are
bonded together by RNA polymerase to form sugar-phosphate backbone
4. the new single-stranded molecule formed is called messenger RNA (mRNA)
5. mRNA leaves nucleus by nuclear pore in nuclear envelope
6. in cytoplasm, there are free amino acids and transfer RNA (tRNA) molecules
7. at one end of each tRNA is a site to which an amino acid can bind
8. at the other end are three unpaired bases called anticodon
9. each tRNA bonds with particular amino acid, controlled by enzyme and ATP
translation
1. in cytoplasm, mRNA attaches to ribosome
2. ribosome made up of ribosomal RNA (rRNA) and protein; contain small/large subunit
3. mRNA binds to small subunit
4. six bases at a time exposed to large subunit
5. first codon always AUG
6. tRNA with the complementary anticodon forms hydrogen bonds with AUG
7. this tRNA has amino acid methionine attached to it
8. second tRNA bonds with the next 3 bases, brings different amino acid
9. two amino acids held close together and peptide bond forms between them
10. this reaction catalyzed by the enzyme peptidyl transferase (found in small subunit)
11. ribosome moves along mRNA to read next 3 bases
12. third tRNA molecule brings third amino acid, joining to second one, first leaves
13. polypeptide chain continues to grow until stop codon exposed (UAA, UAC, UGA)
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phloem
– carries products of photosynthesis
– transports from leaves to rest of plant
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vascular tissue made up of xylem and phloem; sclerenchyma fibers provide extra
both contain more than one type support for stem
of cell; in stems, xylem and
phloem found as vascular
bundles; the outside of bundles
has caps made of sclerenchyma
fibers
TRANSPORT OF WATER
1. water uptake near root tips
2. water enters xylem
3. water moves up xylem
4. water moves from xylem to leaf cells
5. evaporation of water into leaf air spaces
6. transpiration of water vapor through open stomata into air (mainly underside leaf)
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TRANSPIRATION
the loss of water vapor from a plant to its environment by diffusion down a water potential
gradient; most transpiration takes place through stomata in leaves
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xerophytes
plants that live in places where water is in short supply; keep water loss minimal
1. curled leaf
2. sunken stomata
3. cuticle contains cutin, a waterproof substance
4. hairs
5. leaves are needles (reduced surface area)
6. swollen succulent stems (to store water)
7. stomata only at underside of leaf
xylem tissue
1. made from cells joined end to end to form tubes
2. cells are dead
3. walls of cells are thickened with hard strong material called lignin
4. functions: support and transport
5. in flowering plants, xylem tissue contains:
– vessel elements and tracheids: cells that are involved with the transport of ware
– sclerenchyma fibers: elongated, dead, empty cells with lignified walls to support
plant
– parenchyma cells
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root pressure
– increase pressure difference by raising water pressure at the base of vessels
– pressure raised by active secretion of solutes into the water in xylem vessels in roots
– cells surrounding xylem vessels use energy to pump solutes across membranes and into
xylem by active transport
– presence of solutes lowers water potential of the solution in xylem, draws water from
surrounding root cells
– water transport is passive process, driven by transpiration
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TRANSLOCATION
– can be applied to transport in both xylem and phloem
– moving from one place to another
– transport assimilates (sugars from photosynthesis) to sink for storage through sieve
elements and companion cells
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companion cells
– each sieve element has one companion cell beside it
– have ‘normal’ plant cell structure
– very closely associated with sieve element; single functional unit
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movement by mass flow down pressure movement by mass flow down pressure
gradient; through tubes stacked end to end gradient; through tubes stacked end to end
living cells dead cells
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CARDIOVASCULAR SYSTEM
made up of heart and blood vessels
type description
double circulation blood travels twice through the heart on one complete circuit;
has deoxygenated and oxygenated flows; systemic +
pulmonary
systemic circulation blood pumped out of left ventricle into aorta, travels to all
parts of body except lungs, returns to right side of heart in
vena cava; higher blood pressure than pulmonary circ.
pulmonary circulation blood pumped out of right ventricle into pulmonary arteries,
carried to the lungs, return to left side of heart through
pulmonary veins
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BLOOD VESSELS
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veins capillaries join one another to form carries blood toward heart;
venules, which join to form veins;
lower pressure than arteries; has
same three layers of arteries (but
tunica media much thinner, fewer
elastic/muscle fibers); large lumen;
run very close to leg muscle; tensing muscles temporarily raise
pressure;
semilunar valves prevent back flow of blood
capillaries very small; forms network (capillary linking arteries and veins; take blood to
beds); 7µm diameter, about same almost every cell in the body; take
size as RBC; single layer of blood as close to cell as possible to
endothelial cells; has small gaps in reduce distance for substance
endothelium diffusion; gaps for exchange of blood
components
tissue fluid
– leaked plasma that resides in spaces between cells
– identical in composition to blood plasma, but less proteins
– less proteins because they’re too large to fit through gaps of cap. walls
– contains white blood cells
– when blood pressure too high, too much fluid pushed into tissue; build up of tissue fluid
called oedema
– helps with homeostasis (later in A-Level content)
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LYMPH
– lymph: fluid inside lymphatics
– tissue fluid that does not seep back into capillaries (10%)
– returns to blood through lymph vessels or lymphatics
1.lymphatics: tiny blind-ending vessels; found in almost all tissues of the body;
contain tiny valves which allow tissue fluid to flow but not escape; work
like vessels, can contract to put pressure on fluid
2. lymph vessel: many lymphatics joined together; brings blood back to veins
beneath collarbone (subclavian veins)
– valves wide enough to allow large protein molecules to pass, since capillaries too small
– lymph nodes: at intervals along lymph vessels; for protection against disease; remove
bacteria and secrete antibodies
BLOOD
red blood cells (erythrocytes)
– contain haemoglobin: red pigment; 4 haem groups; carries 8 oxygen molecules
– transport oxygen to respiring tissues
– (fetus) RBC formed in liver; (after birth) RBC formed in bone marrow
– structure:
1. biconcave disc: increases surface area; oxygen diffuses faster
2. small: 7µm; can fit in capillaries; haemoglobin close to membrane; quick exchange
3. flexible: can deform to pass through narrower capillaries
4. no nucleus, ER, mitochondria: more room for haemoglobin
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lymphocytes
– secrete antibodies
– smaller than other phagocytes
– large nucleus; small amount of cytoplasm
HAEMOGLOBIN
– transport oxygen (can combine with 8 O molecules)
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s shaped curve
1. when first oxygen molecule combine with a haem group, haemoglobin molecule is slightly
distorted
2. distortion makes it easier for rest of oxygen molecules to combine with second haem
group
3. shape of dissociation curve reflects the binding of oxygen with haemoglobin
Bohr shift
– amount of oxygen haemoglobin carries also affected by partial pressure of CO2
– reactions of CO2 and haemoglobin
carbonic anhydrase
1. CO2 + H 2O ⇌ H2CO3 (carbonic acid)
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high altitude
– lower partial pressure of oxygen the higher the altitude
– haemoglobin becomes less saturated with oxygen
– less oxygen carried around the body
– results in altitude sickness; symptoms:
1. increase in rate and depth of breathing
2. dizziness and weakness
3. arterioles in brain dilate; fluid leaks out of capillaries; cause disorientation
4. fluid also leaks into lungs, prevent them from functioning properly
– altitude sickness can be prevented by adaptation:
1. RBC increases
2. broader chests; greater lung capacity
3. larger heart, especially at right side
THE HEART
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CARDIAC CYCLE
– remember by: A V1 V2
1. atrial systole:
– heart is filled with blood and muscle in atrial walls contract
– blood forced down through atrioventricular valves and enter ventricles
2. ventricular systole:
– 0.1 seconds after atria contract
– ventricles contract
– blood forced into pulmonary artery or aorta (semilunar valves open)
– lasts 0.3 seconds
3. ventricular diastole:
– heart muscle relaxes, pressure in ventricles drops
– semilunar valves close, prevent back flow of blood
– blood from veins flow into atria
4. cycle repeats
name description
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fibrillation
chaotic excitation waves; passes through ventricular muscle in all directions, re-stimulate
areas that have already been stimulated
ELECTROCARDIOGRAM (ECG)
P – atria contracts
QRS – ventricles contract
T – atria and ventricles contract
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GAS EXCHANGE
1. to clean and warm air that enters during breathing
2. maximize surface area for diffusion of oxygen and CO2 between blood and atmosphere
3. minimize distance for diffusion
4. maintain adequate gradients for diffusion
in structure function
COMPONENTS
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ciliated cells
– continual beating of cilia carries mucus upwards toward larynx
– when mucus reaches top of trachea, it gets swallowed and destroyed by stomach acid
macrophages
– patrol surface of airways, scavenging for small particles like bacteria/dust
– during infection, macrophages are joined by phagocytic cells that leave capillaries to help
remove pathogens
ALEVEOLI
– alveolar walls contain elastic fibers that stretch/recoil during in/expiration of air
– elasticity allows expansion according to volume of air breathed in
– expansion increases surface area available for diffusion
– recoil forces out air
– extremely thin walls, pressed closely to capillaries, distance of diffusion small
– steep concentration gradient maintained by breathing and flow of blood
TOBACCO SMOKE
tar
– a carcinogen
– mixture of compounds that settle on lining of airways in lungs and stimulate a series of
changes that leads to obstructive lung disease and lung cancer
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nicotine
– the drug in tobacco; addictive
– absorbed very readily by blood, travels to brain within seconds
– stimulates nervous system to reduce diameter of arterioles and to release adrenaline from
adrenal glands
– heart rate and blood pressure increase, with decrease in blood supply to the extremities,
reducing oxygen supply
– increases risk of blood clotting
carbon monoxide
– forms irreversible carboxyhaemoglobin; reduces chances of oxygen to bind with
haemoglobin
– CO damages lining of arteries, leads to build up of fatty tissue and reduction of blood flow;
result to CHD/stroke
LUNG DISEASES
1. chronic obstructive pulmonary disease (COPD; chronic bronchitis and emphysema)
2. lung cancer
chronic bronchitis
1. tar stimulates goblet cells/mucous glands to enlarge and secrete more mucus
2. tar inhibits cleaning motion of cilia, destroys many of them and weakens remaining ones
3. mucus accumulates in bronchioles
4. dirt/bacteria accumulation stimulates ‘smoker’s cough’
5. damaged epithelia replaced by scar tissue, narrows airways, difficult to breath
6. infections easily develop, lining of lungs become inflamed, further narrows airways
7. damage and obstruction called chronic bronchitis
8. symptoms: severe cough, difficulty breathing
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emphysema
1. inflammation of constantly-infected lungs cause phagocytes to line airways
2. phagocytes release elastase (digests elastin in alveoli) to make pathway for phagocytes
3. alveoli cannot stretch/recoil without elastin
4. bronchioles collapse during expiration, traps air in alveoli, which can burst
5. bursting decreases surface area for diffusion, less oxygen absorbed
6. air cannot be refreshed during ventilation
7. blood vessels in lungs become more resistant to blood flow, pressure in pulmonary artery
increase, right side of heart enlarges
8. symptoms: wheezing, breathlessness
lung cancer
1. tar contains carcinogens that react with DNA in epithelial cells to cause mutation
2. mutations lead to build up of tumor
3. spreads through bronchial epithelium and enters lymphatic tissues
4. cells can break away for secondary growths
5. symptoms: coughing up blood; chest pain; difficulty breathing
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disease illness or disorder of the body or mind that leads to poor health;
each disease is associated with a set of signs and symptoms
pathogen disease-causing organisms
transmission cycle way in which pathogen passes from one host to another
CHOLERA
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MALARIA
control measures:
1. stocking ponds; irrigation; drainage ditches with fish that feed on
mosquitoes
2. spraying a preparation containing bacteria (Bacillus thuringienis)
that kills mosquito larvae but not other forms of life
problems:
1. Plasmodium resistant to drugs
2. mosquitoes resistant to DDT/insecticides
3. expensive
4. difficulties in developing vaccine
5. severe forms of malaria
6. migration of people
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TUBERCULOSIS
methods of prevention:
1. contact tracing
2. vaccine
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MEASLES
pathogen Morbillivirus
ANTIBIOTICS
1. drug that kills/stops growth of bacteria without harming cells of infected organism
2. how they work:
– interfere with growth or metabolism of target bacterium such as:
1. synthesis of bacterial cell walls
2. activity of proteins in the cell surface membrane
3. enzyme action
4. DNA synthesis
5. protein synthesis
3. how penicillin works:
– prevents synthesis of cross-links between peptidoglycan polymers in cell walls of
bacteria by inhibiting enzymes that build the cross-links
– only active against bacteria that are growing
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antibiotic resistance
– vertical transmission:
1. bacterial chromosome and plasmid replicate in resistant parent cell
2. cell division occurs
3. daughter cells each receive a copy of the plasmid and are resistant
– horizontal transmission
1. single DNA strand of plasmid from resistant cell transferred to non-resistant cell by
conjugation
2. conjugation: tube forms between two bacteria to allow DNA movement
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CHAPTER 11 IMMUNITY
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PHAGOCYTES
– produced in bone marrow (myeloid stem cells), stored there before being distributed
through blood
– neutrophils (lobed nuclei)
1. travel throughout body
2. can leave blood by squeezing through capillary walls to patrol tissues
3. short-lived
– macrophages
1. larger than neutrophils
2. found in organs such as lungs, liver, spleen, kidney, lymph nodes
3. made in bone marrow; travel in blood as monocytes
5. long-lived
6. cut up pathogens to display antigens to be recognized by lymphocytes
phagocytosis
1. cells under attack release chemical called histamine, attracting passing neutrophils (called
chemotaxis)
2. neutrophil moves toward pathogen, which may be clustered together and covered with
antibodies
3. antibodies further stimulate the neutrophil to attack pathogens
4. this is because neutrophils have receptor proteins on surfaces that recognize antibody
molecules and attach to them
5. when neutrophil attaches to pathogen, neutrophil’s membrane engulfs pathogen, and
traps it in a phagocytic vacuole (endocytosis)
6. digestive enzymes secreted into phagocytic vacuole to destroy pathogen
7. after killing and digesting pathogens, neutrophil dies
8. dead neutrophil often collect at infection site to form pus
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LYMPHOCYTES
– smaller than phagocytes, large nucleus
– produced in bone marrow (lymphoid stem cells)
B-lymphocytes
– spread throughout body, concentrating in lymph nodes and spleen
– become plasma and memory cells
– maturation:
1. in bone marrow, immature cells divide by mitosis
2. still in bone marrow, each B cell matures
3. mature B cells produce antibody receptors in surface membrane
4. mature B cells circulate and concentrate in liver and spleen
– mode of action:
1. a B cell has specific antibodies to antigen
2. B cell divides by mitosis, daughter cells become plasma/memory cells
3. plasma cells secrete antibodies that bind to antigen
4. when antigen re-enters body, memory cells produced earlier respond by dividing
into plasma cells and more memory cells; second response faster than first due to
memory cells
antibodies
– globular glycoproteins with quaternary structure
– form groups of plasma proteins called immunoglobulins
– consist of four polypeptide chains (two long/heavy chains; two short/light chains)
– disulfide bonds hold chains together
– variable region of one light and one heavy chain make antigen-binding sites
– hinge region between two heavy chains give flexibility in binding to antigen
– heavy chains have chain of sugar molecules attached to them
– functions:
1. combine with virus/toxins
2. attach to bacteria flagella
3. cause agglutination of bacteria
4. coat bacteria, makes it easier for phagocytes ingest them
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T-lymphocytes
– created in bone marrow, and collect in thymus when mature
– helper and killer T cells
– maturation:
1. in bone marrow, immature T cells divide by mitosis
2. in thymus, each T cell matures
3. T cells produce receptors in cell surface membrane
4. mature T cells circulate as helpers/killers
– mode of action:
1. helper/killer T cells binds to antigens of infected body cell
2. helper/killer cells divide by mitosis
3. helper T cells either:
– divide into memory cells
– secrete cytokines that stimulate B cells to divide and form plasma/memory
cells
4. killer T cells either:
– divide into memory cells
– punch holes in cell surface membrane of infected body cell and secrete
toxic substances to kill body cell and pathogen inside
type description
active immunity gained when antigen enters body; immune response occurs
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VACCINES
– preparation containing antigens
– used to stimulate immune response
– artificial active
– given by injection; or taken orally
– problems with vaccines:
1. poor response (do not develop B/T cells)
2. live virus and herd immunity (vaccinate large amounts of people at same time;
herd immunity interrupts transmission in population)
3. antigenic variation (regular mutation)
4. antigenic concealment (pathogen hides in body cells/host proteins)
ERADICATION OF SMALLPOX
– success caused by:
1. variola virus stable
2. vaccine made of harmless strain of similar virus
3. vaccine was freeze-dried and could be kept at high temperatures
4. infected people were easy to identify
5. vaccine easy to administer
6. virus did not linger in body
7. virus did not infect animals
8. teens were enthusiastic vaccinators/suppliers of information
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AUTOIMMUNE DISEASES
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