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Year 13 Biology > A2 Key Mechansims > Flashcards

A2 Key Mechansims Flashcards

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1
Q

4 stages of respiration

A
  • Glycolysis
  • Link reaction/oxidative decarboxylation
  • Krebs cycle
  • Oxidative phosphorylation
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2
Q

Glycolysis mechanism

A

Phosphorylation:

  • One molecule of ATP is hydrolysed and the released phosphoryl group is added to glucose to make hexose Monophosphate
  • Another molecule of ATP is hydrolysed and the phosphoryl group is added to the hexose phosphate to form a molecule of hexose biphosphate
  • The energy from the hydrolysed ATP molecules activated the hexose sugar and prevents it from being transported out of the cell

Splitting the hexose biphosphate:

-Each molecule of hexose biphosphate is split into two three-carbon molecules, triose phosphate, each with a phosphate group attached

Oxidation of triose phosphate to pyruvate:

  • Dehydrogenase enzymes, aided by coenzyme NAD, remove hydrogens from triose phosphate
  • The two molecules of NAD accept the hydrogen atoms(protons and electrons) and become reduced
  • At this stage, two molecules of NAD are reduced for every molecule of glucose undergoing glycolysis
  • Also at this stage, four molecules of ATP are made for every two triose phosphate molecules undergoing oxidation by substrate level phosphorylation

OVERALL:
2 ATP produced
2NADH produced
2 pyruvate produced

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3
Q

Link reaction mechanism

A
  • Pyruvate is decarboxylated and dehydrogenated, catalysed by pyruvate dehydrogenase, which catalysed the sequence of reactions that occur during the link reaction
  • No ATP is produced during this reaction
  • The carboxyl group is removed and is the origin of some of the CO2 produced during respiration
  • Decarboxylation and dehydrogenation of pyruvate produces and acetyl group (dehydrogenation and then decarboxylation)
  • The acetyl group combines with coenzyme A(CoA) to become acetyl CoA
  • The coenzyme NAD becomes reduced (==> 3ATP)
  • Coenzyme A accepts the acetyl group and forms CoA acetyl
  • CoA acetyl carries the acetyl group on to the Krebs cycle
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4
Q

HIV replication mechanism

A
  1. HIV virus consists of RNA genome and two enzymes with a protein capsid
  2. The virus also pinches off some of the lipid membrane from the host cell (which will kill it)
  3. In the lipid membrane it will contain a glycoprotein called GP120
  4. The virus uses GP120 to attach to CD4 receptors on host cells
  5. This tricks white blood cells (phagocytes) into endocytosis
  6. The virus then unwraps its capsid
  7. The RNA is released and the viral enzyme Reverse Transcriptase converts the RNA into duplex DNA
  8. The Duplex DNA penetrates the nucleus
  9. The viral enzyme Integrase will then splice the Duplex DNA into the host genome
  10. The host cell will transcribe the gene and viral proteins will be assembled into new viruses
  11. HIV causes AIDS because the T-helper cell population eventually collapses
  12. This impairs the process of T and B lymphocyte clonal expansion
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5
Q

Synoptic Question - liver and fat metabolism mechanism

A
  • Triglycerides are insoluble in watery blood
  • so the liver packages them into a lipid core with a protein cage called a lipoprotein
  • lipoprotein is soluble in the blood
  • lipoproteins also contain cholesterol
  • if the diet contains a very high amount of fat,
  • the liver is forced to make proteins which have higher proportion of lipid and are less dense than LDL
  • these are less stable and can deposit in arterial walls causing atherosclerosis
  • both LDLs and HDLs are taken up by cells by binding to receptors then being taken in by endocytosis
  • the liver can also both break down lipids and also synthesise them
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6
Q

Atherosclerosis mechanism

A
  1. Endothelial wall is damaged
  2. Risk factors include: smoking, high blood pressure, diabetes, drugs, blood borne diseases, age
  3. The endothelium becomes leaky to cholesterol from the lumen
  4. Cholesterol builds up in the capillary middle layer (tunica intima)
  5. This triggers an immune response
  6. Phagocytes migrate into the area and engulf the cholesterol
  7. This causes the buildup of pus, cholesterol to produce a plaque
  8. The endothelium can tear and the plaque empties into the lumen
  9. This stimulates the production of a blood clot (thrombosis) in the arteries
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7
Q

Light Dependent Reaction/Cyclical Photophosphorylation Mechanism

A
  1. Occurs upon the thylakoid membrane
  2. Light of the correct wavelength strikes the chlorophyll in Photosystem 1
  3. The chlorophyll is photo-ionised and the electron is passed along a chain of membrane-bound carrier proteins
  4. Through a series of redox reactions
  5. Travels to the final electron acceptor NADP+
  6. NADP + H+ + 2e- —> NADPH
  7. The energy of the redox reactions is used by the carrier proteins to pump protons from the stroma
  8. And into the thylakoid lumen to build up a proton gradient
  9. ATP Synthase can harness the energy of the proton gradient to synthesise ATP
  10. ADP + Pi —> ATP
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8
Q

Non-cyclical phosphorylation mechanism

A
  1. In eukaryotic cell, Photosystem 2 has evolved
  2. It uses chlorophyll to harness light energy
  3. This is then used for photolysis of water
  4. H2O —> 2H+ + 2e- + 1/2O2
  5. The electrons are passed along a chain of carrier proteins to Photosystem 1
  6. This allows the ionised chlorophyll to be reduced back into the forums state
  7. It also results in more protons being pumped into the thylakoid lumen
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9
Q

Some bodybuilders use anabolic steroids to increase their muscle mass.
Suggest why anabolic steroids are effective when applied to the surface of the skin.
(2 Marks)

A
  • Skin has a large surface area for absorption
  • Skin has a large network of capillaries
  • Steroids are non-polar
  • So can cross phospholipid bilayer via diffusion
  • Muscles are close to the skin surface
  • so have a short diffusion pathway - quicker rate of diffusion
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10
Q

Muscle contraction - model mechanism

A

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11
Q

Medulla Oblongata and changing heart rate mechanism

A

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12
Q

Describe and explain how the activation of the ‘fight or flight’ response affects voluntary, involuntary and cardiac muscle.
(6 Marks)

A

jehgfkjsehfw

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13
Q

Acetylcholine secretion mechanism

A

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14
Q

All reflex arc mechanisms

A
  1. Knee Jerk Reflex
    - a spinal reflex
    - quadriceps muslce contracts to straighten leg
    - muscle attached to patella tendon
    - stretch receptors detect increase in length of the muscle
    - when muslces at front of the thigh are stretched
    - if stretching is unexpected, reflex causes contraction of the same muscle
    - reflex enables us to balance on two legs
  2. Blinking Reflex
    - retina detects light
    - action potentials travel along sensory neuone
    - action potential then travels alomng a sensory neurone in the brain
    - travels across neuromuscular junction
    - refernce to synpatc transmission
    - depolarisation of muscle fibres occurs
    - reference to muscle contraction
  3. Corneal reflex
    - mediated by sesnory neurone in the cornea
    - which enters the pons
    - sensory neurone connected to relay neurone by synapse
    - this passes action potential to motor neurone
    - passes to facial muscles
    - causes eyelids to blink
  4. Optical Reflex
    - protects light sensitive cells in the retina from damage
    - stimulus detected by the retina
    - response is mediated by the optical centre in the cerebral cortex
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15
Q

What changes occur to the sarcomere during contraction?

1 Mark

A

A band - stays unchanged in length
H zone - shortens
I band - shortens

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16
Q

Different Plant Hormones and their effects

A

Auxins:

  • promote cell elongation
  • maintain apical dominance - inhibit growth of lateral side shoots
  • inhibit leaf and fruit abscission

Abscissic Acid:

  • inhibits seed germination and growth - in less than optimal conditions
  • cause stomatal closure in low water availability
  • apical dominance - inhibit lateral bud growth

Cytokinins:

  • overcome apical dominance
  • delay leaf senescence
  • promote cell division and cell expansion

Giberellins:

  • promote seed germination
  • promote internodal growth of stems

Ethene:

  • promotes leaf abscission
  • promotes fruit ripening
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17
Q

Commercial uses of different plant hormones

A

Auxins:

  • Can be used to produce rooting powders from plant cuttings
  • can be used as weedkillers - promotes rapid shoot growth where the plant cannot support itself and dies
  • can help make seedless fruits

Abscissic Acid:

Cytokinins:

  • prevent yellowing of leaves, e.g. lettuce leaves
  • used in tissue culture to promote growth of side shoots

Giberellins:
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Ethene:

  • speed up ripening in fruits
  • promote fruit abscission in other fruits, e.g. cherries
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18
Q

Mechanism - investigation to prove positive phototropism in plants
(6 points)

A
  1. seijcosiej
  5. 6.
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19
Q

Mechanism for elongation by auxins

A

• Auxins are produced at the apex (tip) of the shoot
• These diffuse down the shoot to the zone of elongation and bind to receptors on
the cells
• This causes H+ ions to be actively transported into the cell wall
• Low pH causes wall loosening enzymes to work by breaking bonds with cellulose -
makes walls more flexible
• Water enters cell and flexible wall allows cell to elongate

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20
Q

Mechanism for phototropism using auxins

A

• Auxins are produced at the apex (tip) of the shoot
• If more light is coming from one side - phototropin enzymes are activated more on
this side
• Phototropins cause PIN proteins to transport more auxins to shaded side
• Cells on the shaded side of the shoot elongate more quickly, causing the shoot to
bend towards the light

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21
Q

Mechanism to prove geotropism

A
  3. 4.
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22
Q

Different tropisms that can occur in plants

A

Phototropism
Geotropism
- Chemotropism
- Thigmotropism

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23
Q

mechanism for geotropism in plants

A
  3. 4.
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24
Q

Why do plants need to respond to their environment?

A
  • Avoid abiotic stress, e.g. weather
  • avoid herbivory/grazing/predation
  • to ensure germination occurs in suitable conditions
  • to maximise photosynthesis, to obtain more light/water/minerals
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25
Q

Action of plant hormones mechanism

A

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26
Q

Compare the actions of plant and animal hormones

6 Marks

A

Similar:

Different:

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27
Q

Outline 3 reasons why plants need to be able to respond to their environment and describe how and why they go about this.
(6 Marks)

A
  1. Why respond:
    - avoid abiotic stresses
    - to maximise photosynthesis - to obtain more light
    - avoid herbivory/grazing
    - ensure seed germination occurs in optimal conditions
  2. Responses:
  • Abiotic stress, e.g. not enough water in surroundings
  • more waxy layer/cuticle in response to water loss
  • prevents water loss
  • Maximise photosynthesis
  • shoots may show positive phototropism
  • increase surface area for sunlight to be absorbed
  • more sunlight abosrbed for more photosynthesis to occur
  • avoid herbivory/grazing
  • production of tannins
  • make the leaves taste bitter
  • animals are less likely to eat them
  • germination in optimal conditions
  • when water is present seeds germinate
  • reason - when seeds absorb water embryo releases gibberellin
  • plant hormone that triggers germination
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28
Q

Describe how the medulla oblongata responds to an increase in CO2 conc. in the blood during exercise.
Explain how this response leads to a decrease in CO2 conc. in the blood.
(7 Marks)

A

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29
Q

Describe and explain all the physiological changes that can occur during the fight and flight response.
(7 Marks)

A

dijcsej

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30
Q

Action of adrenaline

A
  • Adrenaline travels through the blood (1st messenger)
  • Binds to receptors on cell surface membrane of its target cells
  • This causes G-proteins on membrane to activate adenyl cyclase enzymes
  • These convert ATP into cyclic AMP (2nd messenger)
  • This brings about the effect in the cell
31
Q

Controlling heart rate mechanism

A

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32
Q

All plant defences and how they work mechanism

6 Marks

A
  1. Why respond:
    - avoid abiotic stresses
    - to maximise photosynthesis - to obtain more light
    - avoid herbivory/grazing
    - ensure seed germination occurs in optimal conditions
  2. Responses:
    - Abiotic stress
    - more waxy layer/cuticle in response to water loss
    - prevents water loss
  • Maximise photosynthesis
  • shoots may show positive phototropism
  • increase surface area for sunlight to be absorbed
  • more sunlight abosrbed for more photosynthesis to occur
  • avoid herbivory/grazing
  • production of tannins
  • make the leaves taste bitter
  • animals are less likely to eat them
  • germination in optimal conditions
  • when water is present seeds germinate
  • reason - when seeds absorb water embryo releases gibberellin
  • plant hormone that triggers germination
33
Q

What are reflex reactions?

A

Reflexes are rapid responses that dont require conscious thought
- the autonomic nervous system

34
Q

A student setting up an experiment to in vestigate the effect of light on cress plant seedlings accidentally shone the bright light onto one side of the face of another student. He noticed that the student immediately responded by raising her hand to shield her eye from the light.
The response of the cress seedlings to light shining from one direction was slower, but after 24 hours the cress seedlings had grown towards the light.
Describe the mechanisms that produced the responses to light in the cress seedlings and in the human.
(7 Marks)

A
35
Q

Survival value of reflex actions

A
  • used to get out of danger
  • protect body from damage
  • to maintain balance and body position
36
Q

Describe how you would measure the distribution and abundance of plants over a distance of 100 metres.
(6 Marks)

A

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37
Q

Suggest how the adrenaline molecule can cause different effects in different target tissues.
(2 Marks)

A
  • Different tissues have receptors
  • causes cAMP concentration to increase or decrease/ adenyl cyclase inhibited
  • second messenger (cAMP) may be different
  • cAMP activates different enzymes (as opposed to adenyl cylase, etc.)
38
Q

Outline the hormonal and nervous mechanisms involved in the control of heart rate.
(5 Marks)

A

Hormonal:

  • adrenaline increases heart rate
  • secreted from adrenal medulla
  • cardiovascular centre in medulla oblongata

Nervous:

  • SAN controls frequency of waves of excitation
  • controls heart rate
  • action potentials sent across vagus/parasympathetic nerve decrease heart rate
  • action potentials sent across sympathetic nerve increases heart rate
  • high blood pressure detected by baroreceptors
  • low blood pH/increased CO2 levels in blood detected by chemoreceptors
  • barorecpetors and chemoreceptors found in carotid arteries
39
Q

Mechanism - method for practical investigation into effect on auxin on growth of shoots
What will the results be?

A
  1. Take 15 seedlings, cut off tip and measure them
  2. A - to 5 seedlings, cover end of the tip with lanolin (wax)
  3. B - to another 5 - cover end wth lanolin infused IAA
  4. Leave the final 5 untreated
  5. After 3 days re-measure them
  6. Measure the growth of each shoot and calculate the percentage growth
  • A and C wont grow - no auxins
  • B will grow - auxins present
  • C shows that IAA is causing the effect - acts as a control
  • A shows lanolin alone is not causing the effect
40
Q

Mechanism - devise an experiment to show the positive phototropism in plants
(7 points)

A

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41
Q

Outline the role of membranes within cells.

2 Marks

A
  • Compartmentalisation - separates organelles from cell cytoplasm
  • Form named organelles - e.g. vesicles used in transport of substances
  • site of chemical reactions
  • provide attachment sites for enzymes/pigments by formation of receptors
  • allow formation of concentration gradients
42
Q

Plants lose water by transpiration.
Rate of transpiration varies between different species of plant.
Rate of transpiration can be measured using a potometer.

Plan an investigation into the rate of transpiration in two species of plant that would allow valid data to be collected.

Details of how to set up a potometer are not required.
(6 Marks)

A

-

43
Q

Outline the processes involved in the generation of ATP through chemiosomosis.
(6 Marks)

A
  • occurs in mitochondria / on membrane
  • involves inner membrane and matrix
  • involves movement of hydrogen across membrane
  • use of enzyme / channel protein / ATP synthase
  • Hydrogen ions / H+ ions pumped out of matrix across membrane into intermebrane space
  • H+ gradient is created
  • proton motive force is created
  • H+ ions pass from high concentration in matrix to low concentration in intermembrane space
  • H+ ions pass through ATP Synthase
  • ATP is produced when ADP and Pi are joined by conformational shape change of ATP synthase
  • some H+ ions leak back into the matrix - process is not completely efficient
44
Q

It is more difficult for moths and bumblebees (Endotherms) to regulate their body temperature. Explain why.
(2 Marks)

A
  • they are smaller in size than mammals - have a larger SA:V ratio
  • so have a greater rate of heat loss.
  • insects have no thrmoregulatory sensors
  • mammals and birds have more effective and thicker insulation
45
Q

Suggest why blood and faeces have the highest concentration of C-reactive protein and copeptin.
(2 Marks)

A
  • Liver has a good blood supply (via sinusoids)

- liver secretes substances into bile

46
Q

Explain what is meant by the term ‘limiting factor’.

2 Marks

A
  • The factor that will determine the rate
  • when at lower levels/shortest supply
  • e.g. when CO2 conc. is in short supply, it prevents the rate of photosynthesis from increasing
47
Q

Water can fill air spaces in the soil surrounding the roots.
This prevents oxygen from reaching root hair cells.
Using your knowledge of aerobic and anaerobic respiration, explain why overwatering can kill plants.
(6 Marks)

A
  • Filling in air spaces reduces O2 supply for roots
  • less O2 moves into the roots
  • O2 is used in aerobic respiration in the mitochindria
  • O2 used as final electron acceptor in ox. phosph.
  • without O2, aerobic respiration cannot occur
  • Only glycolysis can take place
  • anaerobic respiration takes place
  • lactate fermentation occurs
  • Glucose is converted to pyruvate - ethanal - ethanol
  • allows NADH to be reoxidised an regenerated to NAD
    Effects:
  • less ATP is produced - 2 compared to 32 - in the mitochondria
  • less active transport can occur
  • less minerals and substances can move into the root hair cells
  • less production of amino acids/proteins/DNA/chlorophyll etc.
  • Ethanol is also toxic
48
Q

Explain why podocytes are unable to undergo mitosis.

3 Marks

A
  • already differentiated - so cannot divide by mitosis
  • cells are in G0/resting phase in cell cycle
  • cytoskeleton cannot function - spindle fibres cannot form for mitosis
49
Q

Explain why a plant leaf is described as an organ.

4 Marks

A
  • collection of tissues that work together
  • to achieve a common function
  • collection of phloem, xylem tissues
  • utilised to achieve a common function = photosynthesis
50
Q

What features of adult stem cells make them suitable for regenaration of tissues in the kidney.
(2 Marks)

A

Multipotent
can differentiate into any cell type in the kidney
can differentiate and regenerate into cells that make up kidney tissue, e.g. nephron

51
Q

Pregnancy test mechanism

A

Embryos secrete human chorionic gonadotrophin (hCG) ‐ released in urine during
pregnancy
- hCG is small enough to diffuse from blood through the basement membrane in the Bowmans Capsule and into the filtrate
• hCG acts as antigen
• hCG complementary in shape to free monoclonal antibodies (anti‐hCG)
• binds to free antibodies (with coloured beads on them)
• hCG‐antibody complex moves along the test strip with urine
• hCG‐antibody complex binds with immobilised antibodies specific to the complex
• binding of antibodies produces coloured line (because of coloured beads)
• control antibodies bind with any urine and bind to immobilised antibodies on the
control line to form a coloured strip which indicates the test it working
• 2 lines = pregnant

52
Q

Comment on whether the use of steroids should be allowed in sports.
(3 Marks)

A

oefjoaifja

53
Q

Final electron acceptors for respiration and photosynthesis

A

Respiration: Oxygen
Photosynthesis: NADP

54
Q

PCR test mechanism

A

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55
Q

Electrophoresis of DNA mechanism

A

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56
Q

Electrophoresis of proteins mechanism

A

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57
Q

Uses of electrophoresis (DNA/Proteins)

A

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58
Q

Non Cyclic Phosphorylation Mechanism

A

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59
Q

Cyclic phosphorylation mechanism

A

save my exams webpage

60
Q

Light Dependent reaction - Cyclic photo-Phosphorylation mechanism

A 
Occurs on the thylakoid membrane
Within photosystems (light harvesting complexes)

Cyclic Phosphorylation:
- photosystems of the correct wavelength (red and blue) are absorbed by chlorophyll
- other wavelengths are reflected (usually green)
- chlorophyll is photo-ionised
- in photosystem 1
Ch —> Ch+ + e-

  • the electrons are raised to a higher energy level
  • electrons are passed along a chain of electron carrier proteins
  • through a series of redox reactions
  • to a final electron acceptor - NADP+
    NADP+ + 2e- + H+ —> NADPH
  • the energy of the redox reactions - movement of electrons in the electron transport chain
  • is used to pump protons from the stroma and into the thylakoid lumen
  • this generates a proton gradient which can be harnessed by ATP Synthase to generate ATP
    ADP + Pi —> ATP
  • in prokaryotes the ionised chlorophyll needs to gain an electron ‘from somewhere’ to return to the ground state
  • chlorophyll is oxidised and then reduced - hence cyclic phosphorylation
  • and allow the cycle to continue
61
Q

Light dependent reaction - non-cyclic photo-phosphorylation mechanism

A
  • in eukaryotic cells
  • a second photosystem - photosystem II - has evolved
  • light ionises chlorophyll
  • the energy is used to break a water molecule - photolysis
    H2O —> 1/2 O2 + 2H+ + 2e-
  • electrons are passed along a chain of carrier proteins
  • the redox reactions produce energy
  • energy harnessed to pump protons from stroma into thylakoid lumen
  • so ATP is synthesised at ATP synthase - ADP + Pi —>
  • the final electron acceptor is the ionised chlorophyll from photosystem 1
  • the chlorophyll in cyclic phosphorylation can be reduced to ground state (reduced)
  • this is non-cyclical as:
  • when water is lysed, oxygen is lost from the leaf - diffuses out
  • so water cannot be regenerated
62
Q

Evolution mechanism and acronym- VOSARM

A

V - populations contain genetic variation - caused by mutations
O - Overproduction of offspring
S - Selection Pressure - human impact(?)
S - Survive - organism better adapted more likely to survive
A - Allele variation gives adaptation to current environment
R - Alleles more likely to be passed on by reproduction - organism more likely to reproduce
M - Mutation cases genetic variation

63
Q

Validity def

A

the results that you have only applied to your experiment

- can be improved by obtaining results from other experiements, e.g. results from other laboratories, schools, etc.

63
Q

Validity def

A

the results that you have only applied to your experiment

- can be improved by obtaining results from other experiements, e.g. results from other laboratories, schools, etc.

64
Q

Genetic engineering mechanism - bacteria producing insulin

A

Human pancreatic islet cells subjected to
Cell fractionation and ultra-centrifugal ion
To isolate mRNA
This mRNA has no introns and likely to be used mainly for insulin (beta cells)
A promoter region and a marker gene is attached
mRNA is converted to DNA by reverse transcriptase
A promoter region and marker region is added
Sticky ends are added to each end
Bacterial plasmids are isolated using cell fractionation and ultra-centrifugation
Plasmids cut with a restriction enzyme that will produce the same sticky ends
Mix plasmid with insulin gene
And it will insert due to hydrogen bonds of sticky ends
The sugar phosphate backbone is repealed by DNA ligand in a condensation reaction
To produce a phosphodiester bond
This produces recombinant DNA
Plasmid is reinserted by a few methods:

65
Q

Tissue culture mechanism

A
66
Q

Advantages and disadvantages of tissue culture

A
67
Q

Q)

5 Marks

A

Answers:

68
Q

Why does hyperpolarisation need to occur in neurones?

A

Prevent any stimulus already sent from an axon from travelling another action potential in the opposite direction

69
Q

Describe the similarities between plant and animal hormones.

2 Marks

A
  • bind to target receptors on cells
  • May involve switching genes on/off
  • only needed in small quantities/concentrations to have effect
  • May cause cascade of events/enzyme reactions to occur
  • May have effect on more than one target tissue
70
Q

Conditions for hardy-Weinberg

A
  • no random mutations
  • random mating within population
  • population is large
  • no natural selection favouring particular alleles
  • no migration to introduce or remove alleles from the population
  • none of the genotypes are lethal
71
Q

Epistasis def

A

When the phenotypes of one allele masks the phenotypes of another allele,
E.g. baldness masks the phenotype of brown hair

72
Q

Recessive allele def

A

Allele that is expressed in phenotype on,y in absence of dominant allele

73
Q

Dominant allele def

A

Year 13 Biology (19 decks)

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