CIE paper 4 Flashcards

Question 1

Q

Sorghum is a cereal crop that grows well in very dry (arid) conditions.
(a) Outline two structural features of sorghum that adapt it to survive in arid environments

Answer

A

very extensive root system / roots go very deep ;
small surface area of leaves ; R narrow leaves
leaves roll / presence of hinge cells ; A bulliform
leaves / stalks, have waxy covering / thick cuticle ;
high silica content ;
stomata, reduced in number / in sunken pits ;
idea of supporting tissue ; e.g. sclerenchyma

Question 2

Q

explain why proteins occur in the blood entering the glomerulus but not in the filtrate
in the renal capsule

Answer

A

) (too) large / MM > 68 000 ;

to pass through basement membrane ;

Question 3

Q

explain why there is glucose present in the filtrate but not in the urine

Answer

A

reabsorbed ;

in proximal convoluted tubule ;

Question 4

Q

) explain the difference in the concentration of urea between the filtrate and urine

Answer

A

more urea in urine than in filtrate / ora ; A comparative figs

water is reabsorbed ;
in, distal convoluted tubule / collecting duct ;
most urea stays in urine ; R all urea stays
other substances are reabsorbed ;

Question 5

Q

where in the chloroplast the Calvin cycle occurs

Answer

A

) stroma ;

Question 6

Q

the name of another compound that is produced in the light-dependent stage of
photosynthesis that is used in the Calvin cycle.

Answer

A

ATP / reduced NADP ;

Question 7

Q

Describe the structure of a motor neurone

Answer

A

nucleus in cell body ;
(short), dendrites / dendrons ;
axon ;
(axon) much longer than, dendrite / dendrons ;
must be stated / not on diagram
cell body contains, mitochondria / RER / golgi / groups of ribosomes ;
many mitochondria at, synaptic knob / terminal branch ;
synaptic vesicles ;
neurotransmitter / named neurotransmitter ; linked to 7
Schwann cells / myelin sheath ;
nucleus in Schwann cell ; R nucleus in myelin sheath
node of Ranvier ;
AVP ; e.g. motor end plate / (dendrites) have receptors (for neurotransmitters)

Question 8

Q

Explain how an action potential is transmitted along a motor neurone

Answer

A

Na+
channels open ; A sodium channels
Na+
enter cell ; R enter membrane
inside becomes, less negative / positive / +40mV / depolarised ;
Na+
channels close ; A sodium channels
K+
channels open ; A potassium channels
K+
move out (of cell) ; R of membrane
inside becomes, negative / repolarised ; A negative figure
local circuits / description ;
(myelin sheath / Schwann cells) insulate axon / does not allow movement
of ions ;
action potential / depolarisation, only at nodes (of Ranvier) / gaps ;
saltatory conduction / AW ;
one-way transmission ;
AVP ; e.g. hyperpolarisation / refractory period

Question 9

Q

Explain what is meant by the term endocrine gland.

Answer

A

ductless gland ;

secretes (hormone) into blood ;

Question 10

Q

Explain briefly what is meant by negative feedback.

Answer

A

a change sets off events that counteract the change / AW / example
described ;

Question 11

Q

(a) Describe the process of glycolysis 🤓

Answer

A

(glucose) phosphorylated by ATP ;
raises energy level / overcomes activation energy ;
hexose bisphosphate ;
lysis / splitting, of, glucose / hexose ; R sugar splitting
breaks down to two TP ; A GALP / GADP / G3P / PGAL
6C → 2 x 3C ;
dehydrogenation / description ;
2 NAD reduced formed (from each TP to pyruvate formed) ;
4 ATP produced / net gain of 2 ATP ;
pyruvate produced ;
reduced NAD → oxidative phosphorylation / redox ;
accept flow diagram

Question 12

Q

The optimum temperature for many plants living in temperate regions is approximately
25 °C.
Explain why the rate of photosynthesis in these plants decreases at temperatures above
25 °C

Answer

A

enzymes, denatured / active site changes shape ;
rubisco / enzyme in cyclic photophosphorylation ;
Calvin cycle affected / description ;
less photolysis ;
less ATP produced ;
increased rate of respiration ;
respiration rate faster than photosynthesis rate / ref. compensation
point ;
increased rate of transpiration ;
stomatal closure ;
less CO2 uptake ;

Question 13

Q

a) Describe a reflex arc and explain why such reflex arcs are important

Answer

A

strong stimulus in receptor / AW ;
action potential / impulses, along sensory neurone ;
dorsal root of spinal nerve ;
into spinal cord ;
synapse with intermediate neurone ;
(then) motor neurone ;
action potential / impulses, to effector ;
action potential / impulses, to brain ;
response ; e.g. knee jerk 5 max can be on diagram
fast / immediate ;
stops / limits, damage / danger ;
automatic / no conscious thought ;
innate / stereotyped / instinctive ;

Question 14

Q

Describe the structure of a myelin sheath and explain its role in the speed of transmission
of a nerve impulse.

Answer

A

Schwann cells ;
wrap around axon ;
sheath mainly lipid ;
(sheath) insulates axon (membrane) ;
Na+
 / K+
, cannot pass through sheath / can only pass through
membrane at nodes ;
depolarisation (of axon membrane) cannot occur where there is
sheath / only at nodes of Ranvier ;
local circuits between nodes ;
action potentials ‘jump’ between nodes ;
saltatory conduction ;
increases speed / reduces time, of impulse transmission ;
up to 100 ms-1 ;
speed in non-myelinated neurones about 0.5 ms-1 ;

Question 15

Q

Describe how the liver reduces blood glucose concentration, when insulin is secreted.

Answer

A

binds to receptors (on liver cell membranes) ;

conversion of glucose to glycogen / glycogenesis ;

(because) insulin activates enzyme ; e.g. glucokinase / phosphofructokinase /
glycogen synthase

increased use of glucose in respiration ;

increased uptake of glucose / increased permeability to glucose (of liver
cells) ;

Question 16

Q

With reference to Figs. 4.2 and 4.3, suggest one advantage and one disadvantage of inhaling insulin rather than injecting it.

Answer

A

advantages:

1 faster response time ;

2 less chance of, infection / contamination ;

3 good for people with needle phobia ; max 1

disadvantages :

4 could cause larger swings in blood glucose concentration ;

5 may need to taken more often / not long lasting ;

6 possible variability of dose / AW ;

Question 17

Q

The roots of young rice plants are highly tolerant of ethanol. Explain how this helps them to survive when the fields are flooded.

Answer

A

oxygen availability low (when soil is flooded) ;

plants carry out anaerobic respiration ;

ethanol produced ;

roots can continue to respire ;

Question 18

Q

Outline the role played by accessory pigments in the light-dependent reactions

Answer

A

absorb light ; A harvest light / trap light R collect light

pass energy to, primary pigment / chlorophyll / reaction centre

Question 19

Q

Outline the differences between cyclic and non-cyclic photophosphorylation

Answer

A

cyclic photophosphorylation
electron emitted returns to, PSI / same photosystem or same chlorophyll
molecule ;

non-cyclic photophosphorylation
electron emitted from PSII absorbed by PSI ;

reduced NADP produced ;

photolysis occurs ; A splitting of water

(photolysis) only involves PSII ;

oxygen produced

Question 20

Q

A palisade mesophyll cell is adapted to carry out photosynthesis

Answer

A

show how these adaptations help the cell to carry out photosynthesis.
thin cell wall greater light penetration / short diffusion distance
(for gases) ;

cylindrical shape air spaces ;

large vacuole chloroplasts near outside of cell for better light
absorption / maintains turgor ;

chloroplasts can be moved within the cell absorb maximum light / avoid excessive light
intensities ;

Question 21

Q

Explain the different energy values of carbohydrate, lipid and protein as respiratory substrates.

Answer

A

idea of lipid > protein > carbohydrate / AW ; A lipid has more energy than
either protein or carbohydrate

comparative figures ; e.g. 39.4, 17.0 and 15.8 accept any two

kJ g
1
/ per unit mass ;

more hydrogen atoms in molecule, more energy ;

lipid have more, hydrogen atoms / C-H bonds ;

(most) energy comes from oxidation of hydrogen to water ;

using reduced, NAD / FAD ;

in ETC ;

detail of ETC ;

ATP production

Question 22

Q

Explain how rice plants are adapted for growth with the roots submerged in water

Answer

A

low oxygen (in water) results in anaerobic respiration ;
2. (anaerobic respiration) produces alcohol ;
3. rice tolerant to alcohol ;
4. (because rice has) high levels of, alcohol dehydrogenase / enzyme that breaks down
alcohol ;
5. presence of, aerenchyma / described ;
6. allows, oxygen / air, to reach roots (from aerial tissues)

Question 23

Q

Explain why glucose needs to be converted to hexose bisphosphate

Answer

A

provides activation energy / AW ;

for it to split / AW ;

Question 24

Q

Pyruvate can enter a mitochondrion when oxygen is present.

Describe what happens to pyruvate in a yeast cell when oxygen is not present.

Answer

A

decarboxylated / carbon dioxide given off ;

ethanal produced ;
ethanal reduced ;
by reduced NAD ;
to ethanol ;
dehydrogenase ;

Question 25

Q

State one property of collagen that enables it to carry out its main function in the walls of blood vessels and airways.

Answer

A

high tensile strength / withstands pulling forces / fibrous / insoluble / forms fibrils /
flexible

Question 26

Q

Describe how the structure of a chloroplast is related to its functions.

Answer

A

ground substance / stroma ;

for, light independent stage / Calvin cycle ;
contains enzymes / named enzyme e.g. rubisco ;
also, sugars / lipids / starch / ribosomes / DNA ;
internal membrane system ;
for, light dependent stage ;
fluid-filled sacs / thylakoids ;
grana are stacks of thylakoids ;
(grana) hold (photosynthetic) pigments ;
(grana) have large surface area for (maximum) light absorption ;
(pigments are arranged in), light harvesting clusters / photosystems ;
primary pigment / reaction centre / chlorophyll a, surrounded by accessory pigments ;
(accessory pigments) pass energy to, primary pigment / reaction centre / chlorophyll a ;
different photosystems absorb light at different wavelengths ;
membranes hold, ATP synthase / electron carriers ;
for, photophosphorylation / chemiosmosis ;

Question 27

Q

Describe how you would separate chloroplast pigments using chromatography

Answer

A

. grind leaf with solvent ;
18. example of solvent ; e.g. propanone
19. leaf extract contains mixture of pigments ;
20. ref. concentrate extract ;
21. further detail ; e.g. pencil line drawn / extract placed on chromatography paper /
repetitive spotting / drying between spots
22. paper placed (vertically) in jar of (different) solvent ;
23. solvent rises up paper ;
24. each pigment travels at different speed ;
25. pigments separated as they ascend ;
26. distance moved by each pigment is unique ;
27. Rf value ;
28. two dimensional chromatography ;
29. better separation of pigments

Question 28

Q

Describe how a resting potential is maintained in an axon

Answer

A

axon phospholipid bilayer impermeable to K + / Na
+
;
2. sodium – potassium pump ;
3. detail of sodium-potassium pump ; e.g. transmembrane / globular / ATP binding site
4. active process / ATP used / energy needed ;
5. 3 Na + (pumped) out / 2 K +
(pumped) in ;
6. K + diffuse out / Na
+ diffuse in ;
7. through, protein channels transport proteins ;
8. more K +
channels open than Na +
channels ;
9. therefore, membrane more permeable to K + or more K + leave than Na + enter (axon) ;
10. inside relatively more negative than outside ;
11. –65mV ; A –70mV
12. idea of leaking K +
responsible for resting potential / AW ;
13. electrochemical gradient ;
14. voltage-gated channels closed ; in

Question 29

Q

Describe, using named examples, how sensory receptors in mammals generate action potentials.

Answer

A

general
15. respond to stimuli / AW ;
16. (some) receptors are the ends of sensory neurones ;
17. (some) receptors are cells ;
18. they are energy transducers ;
19. stimulus causes sodium ion channels to open ;
20. sodium ions enter cell ;
21. depolarisation ;
22. receptor / generator, potential ;
23. if (receptor potential) greater than threshold then action potential generated / all or
nothing principle described ;
24. increased stimulus strength leads to increased frequency of action potentials receptor form of energy detected
rods / cones light ;
taste buds / olfactory cells chemical ;
Pacinian \ Meissner’s, corpuscle pressure / touch ;

Question 30

Q

Describe the circumstances in which a.a and lactate are used as respiratory substrates

Answer

A

a.a – starvation / lack of fat or carbohydrate ;

lactate – after anaerobic respiration ;

Question 31

Q

Explain how myelination affects the speed of conduction of impulses

Answer

A

myelin insulates axon ;
no myelin at nodes ;
action potentials / depolarisation, only at nodes (of Ranvier) ;
local circuits set up between nodes ;
action potentials ‘jump’ from node to node / saltatory conduction ;
myelination prevents leakage of ions ; ora

Question 32

Q

Multiple sclerosis (MS) is an auto-immune condition of humans in which the body’s immune system attacks the myelin sheaths which are then damaged. This leads to a decrease in information reaching the brain from sensory receptors.

(i) Suggest how the myelin sheaths may be attacked.
(ii) Explain why this damage leads to a decrease in information reaching the brain from sensory receptors.

Answer

A

(sheath) treated as, ‘foreign’ / non-self ;
1. ref. role of, antibodies / phagocytes / lymphocytes ;
  (ii) 1. less insulation of axon ;
2. action potentials, slow down / stop

Question 33

Q

State precisely the location of photosynthetic pigments within a chloroplast.

Answer

A

grana / thylakoid, membrane

Question 34

Q

summarises the effects of gibberellins on seed germination

Answer

A

When a seed is shed from the parent plant, it is in a state of dormancy,
which means it is metabolically inactive.
When water is absorbed by a seed, it stimulates the production of gibberellin by the
embryo within the seed. The gibberellin stimulates the synthesis of
amylase by cells in the aleurone layer.
Amylase hydrolyses starch molecules in the endosperm converting them
to soluble endosperm molecules. These molecules are converted to
glucose which is transported to the embryo, providing a source of carbohydrate that can be
respired to provide ATP as the embryo begins to grow.
Gibberellin causes these effects by regulating genes that are involved in the synthesis of
amylase. It has been shown that application of gibberellin to seeds can cause an increase in
the transcription of the DNA coding for amylase

Question 35

Q

Outline the role of insulin in a healthy human

Answer

A

1 causes blood glucose concentration, to decrease

/

return to normal (from
high) ;

2 (target cells are) liver

/

muscle ;

3 increased, absorption of glucose (from blood)

/

permeability of cell
surface membrane to glucose ;

4 increased (rate of) respiration of glucose ;

5 idea of increased conversion of glucose to glycogen ;

6 inhibits secretion of glucagon

/

decreased gluconeogenesis ;

Question 36

Q

Describe and explain one advantage of treating diabetics with human insulin produced by rDNA technology.

Answer

A

1 identical to that produced by body ;    2 activity the same
 /
 fast response
 /
 no immune response ;

3 no need for animal insulin

/

AW ;
4 for religious reasons

/

for ethical reasons

/

for e.g. vegetarian ;

5 uncontaminated

/

pure ; 6 so no risk of disease ;

7 production very efficient

/

always available ;    8 extraction from animals, costly
 /
 complex
 /
 limited by supply of animals ;

Question 37

Q

In respiration, energy from various substrates is used to synthesise ATP.
(i) Explain why less ATP can be synthesised from the same mass of glucose in anaerobic respiration than in aerobic respiration.

Answer

A

anaerobic – accept ora for aerobic

1 idea that glucose not completely, broken down

/

oxidised
or only glycolysis occurs ;

2 pyruvate

/

lactate

/

ethanol, still contains energy ;

3 ETC stops ;

4 (because) no oxygen to act as (final) electron acceptor ;

5 (so) no, Krebs cycle

/

link reaction

/

oxidative phosphorylation

/ chemiosmosis ;

Question 38

Q

Explain why more ATP can be synthesised in aerobic respiration from one gram of lipid than from one gram of glucose.

Answer

A

1 lipid contains (relatively) more, hydrogen atoms

/

C-H ;

2 detail ; e.g. molecular formula of glucose and a lipid given

3 more reduced, NAD

/

FAD, produced ;

4 more electrons passed along ETC ;

5 more hydrogen ions pumped across inner mitochondrial membrane

/
more hydrogen ions pumped into intermembrane space

/

steeper proton gradient ;

Question 39

Q

sensory neurone vs motor neurone

Answer

A

B
has many dendrites
is myelinated
may form a synapse with an intermediate neurone
M
cell body lies within the CNS
S
dendron is usually longer than axon 
cell body lies within spinal nerve

Question 40

Q

Describe how an action potential arriving at a presynaptic membrane of a neurone can result in the depolarisation of the membrane of a post-synaptic neurone.

Answer

A

1 Ca(2+) channels open (in presynaptic membrane

/

presynaptic knob) ;

2 Ca2+ enter (pre)synaptic knob ;

3 vesicles contain, neurotransmitter

/

ACh ;

4 (vesicles) move towards

/

fuse with, presynaptic membrane ;

5 (ACh

/

neurotransmitter) released

/

exocytosis ;

6 (ACh

/

neurotransmitter) diffuses (across cleft) ;

7 binds to receptors on postsynaptic membrane ;

8 Na(+) channels open ;

9 Na+ enters post-synaptic neurone

Question 41

Q

Acetylcholinesterase is an enzyme found in the synaptic cleft.
Outline the role of acetylcholinesterase

Answer

A

hydrolyses

/

breaks down, ACh ;

stops continuous production of action potentials (in post-synaptic neurone)

Question 42

Q

Name precisely the process that produces reduced NADP

Answer

A

non-cyclic photophosphorylation ;

Question 43

Q

Describe how carbon dioxide reaches the inside of a palisade mesophyll cell from the external atmosphere

Answer

A

1 enters via stoma(ta) ;

2 by diffusion

/

down a concentration gradient ;

3 passes through air spaces ;

4 dissolves in film of water (on cell surface) ;

5 (diffuses) through cell, wall

/

surface membrane (of palisade cells) ;

Question 44

Q

V The optimum pH for the activity of rubisco is pH8.

Explain why the illumination of chloroplasts leads to optimum pH conditions for rubisco.

Answer

A

1 excited electrons leave, chlorophyll a

/

photosystem ;

2 pass along ETC ;

3 protons present from photolysis ;

4 protons (pumped) into intermembrane space ;

5 rubisco is in stroma ;

6 idea that protons leaving stroma raises pH

Question 45

Q

) Describe and explain how gibberellins are involved in the germination of wheat or barley seeds.

Answer

A

1 seed is, dormant

/

metabolically inactive ;

2 water enters seed ;

3 embryo, produces

/

releases, gibberellin ;

4 gibberellin stimulates aleurone layer ;

5 (by) affecting, gene coding

/

transcription of mRNA, for amylase ;

6 to produce amylase ;

7 amylase hydrolyses starch ;

8 in endosperm ;

9 to, maltose

/

glucose ;

10 embryo uses sugars for respiration ;

11 energy

/

ATP, used for growth ;

Question 46

Q

Explain the principles of homeostasis in humans.

Answer

A

1 (homeostasis is) maintenance of, constant

/

stable, internal environment ;

2 irrespective of changes in external environment ;

3 negative feedback ;

4 ref. to input

/

stimulus ;

5 receptor detects change in parameter ;

6 action taken by effector

/

response

/

AW ;

7 restoration of, norm

/

set point

/

AW ;

8 ref. to fluctuation around the norm ;

9 example of homeostasis ;

Question 47

Q

Outline the effect of ADH on the collecting ducts.

Answer

A

1 ref. to enzyme / phosphorylase / signalling ;

2 ref. to aquaporins ;

3 vesicles (containing aquaporins), move towards / fuse with, (cell surface membrane) ;

4 idea of increased permeability ;

5 water leaves (lumen into cells), by osmosis / down water potential gradient ;

Question 48

Q

Describe the role of rubisco in the Calvin cycle

Answer

A

1 fixation of carbon (dioxide) ;

2 (catalyses) the reaction between RuBP and CO2 / AW ;

3 to give two GP ;

4 via an unstable intermediate compound ;

Question 49

Q

Outline how an action potential arriving at this neuromuscular junction can result in depolarisation of the sarcolemma.

Answer

A

1 Ca2+ channels open in, pre-synaptic membrane / (pre)-synaptic knob / motor end plate ;

2 Ca2+ enter, pre-synaptic knob / pre-synaptic neurone / motor end plate ;

3 vesicles contain, neurotransmitter / ACh ;

4 (vesicles) move towards / fuse, with pre-synaptic membrane ;

5 (ACh / neurotransmitter) released / exocytosis, and diffuses (across cleft) ;

6 6. binds to receptors on sarcolemma ; A post-synaptic membrane

7 Na+ channels open and Na+ enters, (muscle fibre / sarcoplasm) ; R sarcolemma

Question 50

Q

Describe the role of oxygen in aerobic respiration

Answer

A

three from 1 used in, oxidative phosphorylation / ETC ;

2 final electron acceptor ;

3 proton acceptor ;

4 forms water ;

5 allows ETC to continue ;

6 ref. to ATP produced ;
3

Question 51

Q

Using examples, outline the importance of homeostasis in a mammal

Answer

A

seven from 1 ref. to maintenance of constant internal environment ;

2 blood or tissue fluid as e.g. of internal environment ;

3 ref. to norm / optimum value / set point / within narrow limits ;

4 (low) temperature and consequence ; e.g. slowed metabolism / enzymes less active

5 (high) temperature and consequence ; e.g. enzymes denatured

6 (low) water potential and consequence ; e.g. water leaving cells / cells shrink

7 (high) water potential and consequence ; e.g. water enters cells / cells burst

8 (low) blood glucose and consequence ; e.g. effect on respiration

9 (high) blood glucose and consequence ; e.g. water leaving cells / cells shrink

10 AVP ; e.g. control of pH and consequence
7

Question 52

Q

Describe the main stages of cell signalling in the control of blood glucose concentration by adrenaline.

Answer

A

1 adrenaline binds to receptors ;

2 in, cell surface membrane / plasma membrane ;

3 receptor changes conformation ;

4 G proteins activated ;

5 adenylyl cyclase activated ; A adenyl cyclase

6 cyclic AMP / cAMP, made ;

7 second messenger ;

8 activates kinase (protein) ;

9 ref. to enzyme cascade / signal amplification ;

10 ref. to phosphorylase ;

11 glycogen broken to glucose / glycogenolysis ;

12 glucose diffuses, out of cells / into blood ;

13 increase in blood glucose concentration ;
8

Question 53

Q

) Explain the role of auxin in cell elongation in plants.

Answer

A

1 acid-growth (hypothesis) ;

2 auxin stimulates proton pumps ;

3 (in) cell surface membrane ;

4 H+ pumped into cell wall ;

5 using energy / by active transport ;

6 pH of cell wall decreases / cell wall becomes (more) acidic ;

7 pH-dependent enzymes activated ;

8 ref. to expansins ;

9 bonds between cellulose microfibrils broken ;

10 idea that cell wall, ‘loosens’ / becomes more elastic / able to stretch ;

11 (more) water enters cell / turgor pressure increases ;

12 (so) cell (wall) expands

Question 54

Q

(b) Describe the role of abscisic acid in the closure of stomata

Answer

A

1 plant secretes abscisic acid, in very dry conditions / at times of water stress ; A abscisic acid is a stress hormone

2 abscisic acid binds to receptors ;

3 on cell surface membranes of guard cells ;

4 inhibits proton pump / H+ not pumped out of cell ;

5 high H+ conc inside cell ; A ref. to change in charge

6 (abscisic acid) stimulates Ca2+ influx ;

7 Ca2+ acts as second messenger ;

8 encourages K+ efflux / inhibits K+ influx ; A K+ channels open

9 water potential of cell increases ; A increase in solute potential

10 water moves out of cell by osmosis ;

11 volume of guard cells decreases ;

12 guard cells become flaccid ;

13 response very fast ;
8

Question 55

Q

State what is meant by the term respiratory quotient (RQ

Answer

A

RQ = volume of carbon dioxide given off; R amount A moles volume of oxygen taken up

Question 56

Q

Explain why an increase in temperature from 15 oC to 25 oC will increase the rate of oxygen uptake in germinating seeds.

Answer

A

ref. effect of temperature on enzymes in respiration; ref. named effect of temperature e.g. increased collisions/kinetic energy/more substrate molecules with activation energy; ref. to Q10 = 2

Question 57

Q

State precisely where the Calvin cycle occurs in plant cells

Answer

A

stroma of chloroplast;

Question 58

Q

b) Describe how carbon dioxide is fixed in the Calvin cycle.

Answer

A

combines with (5C compound) RuBP; to form unstable 6C compound/forms 2 molecules of (3C) GP; ref. enzyme/rubisco;

Question 59

Q

Explain how the products of photophosphorylation are used in the Calvin cycle.

Answer

A

reduced NADP and ATP; (ATP is) source of energy; (reduced NADP is for) reduction of GP(PGA) to triose phosphate (TP); ref. use of ATP in regeneration of RuBP; ref. to source of phosphate/phosphorylation;

Question 60

Q

Explain what initially happens to the concentration of RuBP and GP if the supply of carbon dioxide is reduced.

Answer

A

RuBP, accumulates/goes up; due to reduced combination with CO2/AW; in either RuBP or GP, not both GP, goes down/not as much being formed; due to conversion to TP;

Question 61

Q

Explain how a synapse functions.

Answer

A

1 depolarisation/action potential; 2 of presynaptic membrane/synaptic knob; 3 opening calcium ion channels; 4 calcium ions in; 5 vesicles containing transmitter/acetylcholine; 6 fuse with membrane; 7 contents emptied into synaptic cleft/exocytosis; 8 transmitter/acetylcholine diffuses across synaptic cleft; 9 transmitter/acetychloine binds to receptor; R protein channel 10 on post synaptic membrane; 11 Na+ channels open/NA+ enters; 12 depolarises post synaptic membrane; 13 action potential set up/impulse transmitted 14 breakdown/hydrolysis of transmitter/acetylcholine by enzyme/cholinesterase

Question 62

Q

Describe the role of glucagon in regulating blood gl

Answer

A

5 when blood glucose levels low; 16 glucagon released from alpha cells (in pancreas); 17 (acts on ) liver (cells); 18 breakdown of glycogen to glucose; 19 use of fatty acides in respiration; R fats 20 production of glucose from other compounds/fats/amino acids/gluconeogenesis; 21 liver releases glucose into blood; 22 glucose levels rise/return to normal; 23 switching off glucagon secretion; 24 antagonistic to insulin;

Question 63

Q

Name the membrane-bound enzyme responsible for phosphorylating ADP to make ATP.

Answer

A

ATP, synthase / synthetase ; R ATPase

Question 64

Q

State one use of glucose within the liver cell

Answer

A

(converted to) glycogen / lipid ; (used in) glycolysis / respiration

Answer 65

A

anaerobic less ATP / only 2 ATP ; per mol glucose ; lactate still contains energy / only glycolysis involved / stages other than glycolysis not involved ; not sustainable / cannot go on indeﬁ nitely / AW ;

Answer 66

A

cannot pass through phospholipid bilayer ; too big to ﬁ t through (glucose’s) protein channel ; no speciﬁ c transport protein ; AVP ; e.g. used up as soon as it is made

Answer 67

A

oxygen debt

Answer 68

A

(ii) ﬂ uid can pass through glomerular capillaries because fenestrations in capillary endothelium ; A hole / pores / gaps basement membrane acts as a ﬁ lter ; no substances > 68 000 MM can get through ; no cells can get through ;

Answer 69

A

produce ATP / provide energy ; for active transport of Na+ ; out (of cell) ;

Answer 70

A

mark ﬁ rst two answers any named ion / mineral ions ; vitamins ; amino acids ; glucose ; some urea ;

Answer 71

A

receptors) on plasma / cell surface, membrane (of guard cells) ;

Answer 72

A

(iii) (guard cell has) higher water potential than epidermal cell ; ora

Answer 73

A

(iv) decrease

Answer 74

A

it is identical to human insulin / fits membrane receptor on (target) cells ;

(more) rapid response ;

no / fewer, rejection problems / side effects / allergic reactions ;

ref. to ethical / moral / religious, issues ;

cheaper to produce in large volume / unlimited availability ; R cheap to produce

less risk of, transmitting disease / infection ;

good for people who have developed tolerance to animal insulin

Answer 75

A

islets of Langerhans ;

scattered throughout pancreas / AW ;

alpha and beta cells ;

blood supply (to carry hormones away) ;

Answer 76

A

low blood glucose concentration / during or after exercise ; R sugar

Answer 77

A

foreign / non-self / cell recognition ;

stimulates immune response / AW

Answer 78

A

acetyl CoA combines with oxaloacetate ;

to form citrate ;

4C to 6C ;

decarboxylation / CO2 released ;

dehydrogenation / oxidaextion / release of hydrogen ;

reduced NAD produced / NAD accepts hydrogen ;

reduced FAD produced / FAD accepts hydrogen ;

ATP produced ;

substrate level phosphorylation ;

series of, steps / intermediates ; A many named steps off a diagram

enzyme catalysed reactions ;

oxaloacaetate regenerated ;

occurs in mitochondrial matrix

Answer 79

A

coenzyme ;

for dehydrogenase ;

reduced ;

carries, electrons and protons / hydrogen / NAD

from Krebs cycle ;

and glycolysis ;

to ETC / electron carrier chain / oxidation ;

reoxidised / regenerated hydrogen removed ;

ATP produced ; ex

Answer 80

A

action potential / depolarisation, reaches presynaptic membrane ;

(Ca2+) channels open in presynaptic membrane / presynaptic membrane becomes more permeable to (Ca2+) ; R calcium / Ca / Ca+

Ca2+ (flood) into presynaptic, neurone / knob ; R membrane

(this causes) vesicles of, acetylcholine / ACh ;

(to) move towards presynaptic membrane / (to) fuse with presynaptic membrane;

ACh released into synaptic cleft / exocytosis of ACh ;

ACh diffuses across (cleft) ;

ACh binds to receptor (proteins) / AW ;

on postsynaptic membrane ;

proteins change shape / channels open ;

sodium ions (rush) into postsynaptic neurone ; R membrane

postsynaptic membrane depolarised ;

action potential / nerve impulse ;

action of acetylcholinesterase ;

Answer 81

A

ensure one-way transmission;

receptor (proteins) only in postsynaptic, membrane / neurone ; ora

vesicles only in presynaptic neurone ; ora

adaptation / ACh amount reduces due to overuse of synapse ;

wide range of responses ;

due to interconnection of many nerve pathways ;

inhibitory synapses affect other synapses ;

involved in memory / learning ;

due to new synapses being formed ;

summation / discrimination ;

Answer 82

A

idea of lipid > protein > carbohydrate / AW ; A lipid has more energy than
either protein or carbohydrate

comparative figures ; e.g. 39.4, 17.0 and 15.8 accept any two

kJ g
1
/ per unit mass ;

more hydrogen atoms in molecule, more energy ;

lipid have more, hydrogen atoms / C-H bonds ;

(most) energy comes from oxidation of hydrogen to water ;

using reduced, NAD / FAD ;

in ETC ;

detail of ETC ;

ATP production

Answer 83

A

vesicles found only in presynaptic neurone / ACh released only from presynaptic neurone or membrane ;

receptor (proteins) found only on postsynaptic membrane ;

Answer 84

A

allows more interconnection of nerve pathways / AW ; 2. for, memory / AW ; ignore learning 3. allows wider range of responses ; 4. AVP ; e.g summation

Answer 85

A

raise chemical PE of glucose / provide activation energy

Answer 86

A

removes hydrogen / hydrogen carrier / coenzyme

Answer 87

A

dehydrogenation ; A oxidation decarboxylation ; accept ‘oxidative decarboxylation’ for two marks

Answer 88

A

accepted by NAD ; 2. passed to ETC ; 3. for oxidative phosphorylation ; 4. ref. proton pump / chemiosmosis

Answer 89

A

chlorophyll a is primary pigment ; 2. carotenoids / chlorophyll b, is accessory pigment ; 3. arranged in, light harvesting clusters / photosystems ; A antenna complex 4. on, grana / thylakoids ; 5. ref. PI and PII ; A P700 and P680 6. primary pigment / chlorophyll a, in reaction centre ; 7. accessory pigments / carotenoids / chlorophyll b, surround primary pigment ; 8. light energy absorbed by, accessory pigments / carotenoids / chlorophyll b ; 9. (energy) passed on to, primary pigment / chlorophyll a / reaction centre ; 10. chlorophyll a and b absorb light in red and blue/violet region ; 11. carotenoids absorb light in blue/violet region ; 12. ref. absorption spectrum peaks ; 13. diagram of absorption spectrum ; 14. different combinations of pigments (in different plants) give different spectra

Answer 90

A

IAA / plant growth regulator / plant growth substance / plant hormone ; 16. synthesised in, growing tips / apical buds / meristems ; 17. moves by, diffusion / active transport ; 18. from cell to cell ; 19. also, mass flow / in phloem ; 20. stimulates cell elongation ; R cell enlargement 21. inhibits, side / lateral, buds / growth ; A inhibits branching 22. plant grows, upwards / taller or allows stem to grow up to light (instead of sprouting ) ; A stem elongates 23. auxin not solely responsible for apical dominance or there is interaction between auxin and other plant growth regulators ; 24. ref. idea of concentration gradient down shoot so effect of dominance decreases ; 25. AVP ; e.g. role of ABA and lateral bud inhibition / cytokinins antagonistic to IAA / gibberellins enhance IAA also mp 23

Answer 91

A

H2O 2H
+ + 2e
+ ½ O2 ;

A 2H2O 4H
+ + 4e
+ O2

Answer 92

A

hydrophilic / polar / charged, outside / at surface ; hydrophobic / non-polar / non-charged, inside ; globular (protein) ; ref. to polar interactions / hydrogen bonds, with water (molecules)

Answer 93

A

Calvin cycle / light independent reaction, stops ; no RuBP (for rubisco) ; as no, ATP ; as no reduced NADP ; as no, light dependent reaction / photophosphorylation

Answer 94

A

two from no (new) CO2 fixed / (previously) fixed carbon lost as CO2 ; photosynthesis decreased ; less, RuBP (re)generated / available ; less, TP / glucose, will be made ; energy / ATP, used in making RuBP wasted

Answer 95

A

1 calcium ions / Ca2+, ions from sarcoplasmic reticulum ; 2 calcium ions / Ca2+, bind to troponin ; 3 troponin changes shape ;

4 tropomyosin moves ; 5 from / exposing, (myosin) binding site on actin ; 6 myosin head binds (to actin) ;

7 myosin head tilts / power stroke occurs ; 8 actin pulled ;

Answer 96

A

synthesise / produce, ATP ;

(ATP needed to) synthesise acetylcholine ; (ATP needed for) movement of vesicles / exocytosis ; (ATP needed to) transport calcium ions, out of presynaptic neurone / into sarcoplasmic reticulum ; (ATP needed to) synthesise acetylcholinesterase ; (ATP needed for) Na+(– K+) pumps / pumping / active transport ;
3A

Answer 97

A

1 reduced NAD (used) in both; 2 NAD regenerated / glycolysis can continue, in both;

Differencences 
yeast / ethanol decarboxylation 
two steps / pyruvate → ethanal → ethanol
ethanol dehydrogenase 
decarboxylation

mammalian tissue / lactate
no decarboxylation
reversible
one step / pyruvate → lactate pyruvate accepts H lactate dehydrogenase

Answer 98

A

1 (happens in) proximal convoluted tubule ; 2 all / 100%, glucose (reabsorbed / moves into blood) ; 3 active transport / pumping, of Na+ out of cells into tissue fluid ;

4 Na+ concentration decreases inside cells ; 5 therefore Na+ enters (epithelial / tubule) cells from, lumen / filtrate ; 6 by facilitated diffusion ; 7 this is secondary active transport ; 8 Na+ brings glucose with it ; 9 this is co-transport ; 10 (facilitated) diffusion of glucose out of cells into tissue fluid ; 11 GLUT proteins (on basolateral membranes) ; 12 ref. to microvilli (on lumen side / apical membrane) ; 13 to increase surface area for reabsorption ; 14 tight junctions separate proteins of front and basolateral membranes ;
8A

Answer 99

A

seven from 1 (low blood water potential) detected by osmoreceptors ; 2 in hypothalamus ; 3 neurosecretory cells (stimulated to) produce ADH ; 4 ADH released by posterior pituitary ; 5 ADH transport in blood ; 6 (ADH) binds to receptors (on cell surface membranes) ; 7 (of) collecting duct / distal convoluted tubule ; 8 aquaporins / water transport proteins, added to membranes ; 9 increases permeability to water (of collecting duct / distal convoluted tubule) ; 10 water moves out of, filtrate / tubule lumen ; 11 by osmosis ; 12 into, interstitial fluid / tissue fluid / blood / capillaries ; 13 small volume of / concentrated, urine produced ; 14 increases water potential of blood (back to norm) ;
7

Answer 100

A

1 mechanical energy converted to electrical ; 2 ref. to sensory hair cell (is receptor / detects touch) ; 3 cell membrane depolarises ; 4 (if at least) two hairs touched (within 35 seconds) ; 5 action potential occurs ; 6 action potential / depolarisation, spreads over, leaf / lobe ; 7 ref. to hinge / midrib, cells ; 8 H+, pumped out of cells / pumped into cell walls ; 9 cell wall, loosens / cross-links broken ; 10 calcium pectate dissolves (in middle lamella) ; 11 Ca2+ (ions) enter cells ; 12 water, enters / follows, by osmosis ; 13 cells, expand / become turgid ; 14 change from convex to concave ; 15 trap shuts, quickly / in <1s / in 0.3s ; 16 AVP; acid growth hypothesis / expansins / elastic tension

Answer 101

A

control 1 gibberellin synthesis / dwarfism, controlled by gene Le / le ; 2 dominant allele / Le, gives, functional enzyme / active gibberellin ; ora 3 enzyme converts inactive to active gibberellin ;

stem elongation 4 without GA, transcription factor / PIF, attached to DELLA protein ; 5 GA binds to receptor (complex) ; 6 causes DELLA (protein) destruction ; 7 transcription factor / PIF / RNA polymerase, binds to DNA ; 8 (growth) genes, switched on / expressed / transcribed ; 9 causes cell division ; 10 causes cell elongation ; 11 increases internode length ; 12 loosens cell walls / acid growth ; 13 so cells can expand when water enters ; 14 AVP ; e.g. interaction with auxin, ref. to expansins

Answer 102

A

1 less

/

decreased (aerobic respiration) ;

2 oxygen, is the final electron acceptor

/

needed for ETC ;

3 oxidative phosphorylation decreased

/

chemiosmosis decreased ;

4 regeneration of NAD

/

Kreb’s cycle

/

link reaction, decreased ;

5 ATP synthesis decreases

/

ATP synthetase activity decreased

Answer 103

A

high blood pressure in glomerulus ;

2 (due to) greater diameter of afferent vessel ; ora

3 molecules pass through holes in (capillary) endothelium ;

4 basement membrane selectively permeable

/

only small molecules pass
through basement membrane

/

large molecules unable to pass through
basement membrane ;

5 less than 69 000 RMM ;

6 molecules pass between gaps in podocytes ;

7 enter renal capsule

Answer 104

A

can be done at home / easy to use / non-invasive ;

cheap ;

result produced quickly ;

result likely to be accurate ;

can be done early in pregnancy ;

safe to use

Answer 105

A

1 identical (antibodies) or produced by cloning ;

2 variable regions / antigen binding sites, all identical
or (antibodies) are specific to one antigen ;

Answer 106

A

1 water leaves mitochondrion ; A other named organelle

2 by osmosis / down water potential gradient ;

3 idea mechanical disruption to membranes ;

4 membranes made of phospholipid (bilayer) ;

5 hydrophilic heads / glycoproteins / glycolipids, form fewer hydrogen
bonds with water ;

6 reduces, stability / fluidity (of membrane) ;

7 ref. (proteins with) hydrophilic channels ;

Answer 107

A

removal / elimination, of waste products ;

of metabolism ;

(which are) toxic ;

(or) substances excess (to requirements

Answer 108

A

homeostasis / AW ;

change in water potential ;

detected by (osmo)receptors ;

in hypothalamus ;

response via effector ;

ADH released ;

effect on collecting duct ;

return to, norm / set point

Answer 109

A

ATP ;

reduced NADP
1 ATP provides energy ;

2 reduced NADP, is reducing agent / provides hydrogen ;

3 for converting GP to TP ;

4 (ATP used to) regenerate RuBP

Answer 110

A

process / photosynthesis, affected by more than one factor ;

rate is limited by the factor nearest its minimum value /

Answer 111

A

enters leaf through (open) stomata ;

by diffusion ;

substomatal air space ;

many air spaces in spongy mesophyll ;

spaces between palisade cells ;

dissolves in moisture on cell (walls) ;

enters through cell walls ;

Answer 112

A

Pyruvate, cannot enter mitochondrion / remains in the cytoplasm ;

becomes, hydrogen acceptor / reduced ;

by reduced NAD ;

from glycolysis ;

converted to lactate ;

lactate dehydrogenase ;

allows glycolysis to continue ;

no, decarboxylation / CO2 removed ;

single step ;

reversible reaction / converted back to pyruvate ;

by oxidation ;

ref. oxygen debt ;

ethanol produced ;

Answer 113

A

in mammals

lactate produced / no ethanol produced ;
no, decarboxylation / carbon dioxide released ;
single step ;
lactate dehydrogenase ;
reversible ;

Answer 114

A

in anaerobic respiration

only glycolysis occurs / Krebs cycle stops / link reaction stops ;
glucose, not fully broken down / still contains energy ;
pyruvate does not enter mitochondrion ;
(no oxygen) so no final electron acceptor (in ETC) ;
ETC stops ;
no oxidative phosphorylation

Answer 115

A

affects liver cells ; R muscle cells / liver and muscle cells
promotes glycogenolysis / AW ;
promotes use of fatty acids in respiration ;
promotes gluconeogenesis / AW ;
results in rise in (blood) glucose concentration ;
back to, norm / set point

Answer 116

A

myelin sheath insulates axon ;
idea of depolarisation / action potentials, only at nodes of Ranvier ;
ref. saltatory conduction / AW ;

Answer 117

A

closely packed to absorb (maximum) light ;
vertical / at right angles to surface of leaf to reduce number of cross walls ;
large vacuole pushes chloroplasts to edge of cell ;
chloroplasts at edge short diffusion path for carbon dioxide ;
chloroplasts at edge to absorb (maximum) light ;
large number of chloroplasts to absorb (maximum) light ;
cylindrical cells or air spaces to circulate gases / provide a reservoir of CO2 ;
moist cell surfaces for diffusion of gases ;
cell walls thin for (maximum) light penetration / diffusion (of gases) ;
chloroplasts can move towards light to absorb (maximum) light ;
chloroplasts can move away from high light intensity to avoid damage

Answer 118

A

) accept annotated diagram
12. arranged in light harvesting, clusters / system ;
13. primary pigments / chlorophyll a ;
14. at reaction centre ;
15. P700 / PI, absorbs at 700(nm) ;
16. P680 / PII, absorbs at 680(nm) ;
17. accessory pigments / chlorophyll b / carotenoids, surround, primary pigment / reaction
centre / chlorophyll a ;
18. pass energy to, primary pigment / reaction centre / chlorophyll a ;
19. P700 / PI, involved (in cyclic photophosphorylation) ;
20. (light absorbed results in) electron excited / AW ;
21. emitted from, chlorophyll / photosystem ;
22. flows along, chain of electron carriers / ETC ;
23. ATP synthesis ;
24. electron returns to, P700 / PI ;

Answer 119

A

) 13. (haemophilia) allele on X chromosome ; A gene
14. sex-linked ;
15. (haemophilia) allele recessive ;
16. man, homogametic / has one X chromosome ;
17. Y chromosome does not have blood clotting gene ;
18. only daughter(s) get his X chromosome ;
19. daughter(s) carrier(s) of (haemophilia) allele ;
20. grandson(s) 50% chance of having, (haemophilia) allele / haemophilia ;
21. granddaughter(s) 50% chance of carrying, (haemophilia) allele ;
allow following marks from diagram
22. correct symbols ; e.g. X H
and X h
explained

  23. man’s genotype ; e.g. X h
Y   ignore partner’s genotype 
  2 4. F1 (daughter’s) genotype ; e.g. X H
X
h
   ignore her partner’s genotype 
  2 5. F2 (grandson’s) genotypes ; e.g. X
h
Y   X
H
Y   both required 
  2 6. F2 (granddaughter’s) genotypes ; e.g. X H X H   X H X h   both required   or X h X h   X H X h

Answer 120

A

1 produces ATP ; (1) R produces energy any two from 2 (for) ACh production ; 3 (for) vesicle formation ; 4 (for) vesicle movement ; 5 (for) exocytosis / described ; 6 (for) functioning of ion pumps ; R calcium ions (2 max)

Answer 121

A

1 plasmids (easily) transferred between bacteria ; 2 (bacteria of), same species / different species ; 3 bacteria can acquire antibiotic resistance / renders antibiotic useless

Answer 122

A

1 NAD regenerated ; 2 so glycolysis can continue ; 3 to produce ATP ;

Answer 123

A

1 PII absorbs light ; 2 enzyme (in PII) involved ; 3 to break down water / AW ;
4 2H2O 4H+ + 4e– + O2 ; 5 oxygen is produced ; 6 used by cells for (aerobic) respiration ; 7 or released (out of plant) through stomata ; 8 protons used to reduce NADP ; 9 with electrons from PI ; 10 reduced NADP used in, light independent stage / Calvin cycle ; 11 to convert GP to TP ; 12 electrons also used in ETC ; 13 to release energy for photophosphorylation ; 14 to produce ATP ; 15 electrons (from PII) go to PI ; 16 ref. re-stabilise PI ; [10 max]

Answer 124

A

16 gibberellin is a, plant growth regulator / plant hormone / plant growth substance ; 17 stimulates cell division ; 18 stimulates cell elongation ; 19 detail of cell elongation ; e.g. changes plasticity of cell wall 20 plant grows tall ; 21 apply gibberellin to dwarf plants and they grow taller / gibberellin promotes bolting of some rosette plants ; 22 ref. inactive and active forms ; 23 dwarf plants, lack active form / have inactive form, of gibberellin ; 24 (dominant) allele causes synthesis of enzyme ; 25 (enzyme) catalyses the production of the active form of gibberellin ; 26 recessive allele only inactive form of gibberellin formed / dominant allele results in active form of gibberellins ; 27 AVP ; e.g. ref. to different forms of gibberellins / there is interaction between / gibberellin and other plant growth regulators

Answer 125

A

(stick / kit) dipped in (early morning) urine sample ;
hCG / urine, moves up strip ;
idea that hCG acts as antigen ;
(mobile) antibody also bound to, indicator / gold ;
(mobile) antibody in stick binds to hCG ;
ref. to variable region (of antibody) ;
ref. to specificity (of antibody) ;
ref. to monoclonal (antibody) ;

first window or region
9. second antibody is, immobilised / fixed ;

first antibody and hCG complex binds to second antibody ;
coloured band indicates pregnancy ;

second window or region
12. immobile antibody binds to mobile antibody-gold complex ;

second coloured band shows strip is working

Answer 126

A

rise in blood glucose concentration detected by β cells ;
(β cells) in, islets of Langerhans / pancreas ;
insulin released into blood ;
binds to receptors in cell surface membrane ;
ref. to liver / muscle, cells ;
increase in uptake of glucose (by cells) /
(cell surface) membrane more permeable to glucose ;
increase in use of glucose in respiration ;
(increase in) conversion of glucose to glycogen ;
blood glucose concentration falls ;
inhibits, glycogen / lipid / amino acid, breakdown

Answer 127

A

Auxin is synthesised in the growing tips of shoots (apical buds). It is transported from here
down the shoot by active transport / diffusion from cell to cell and also to a lesser extent
by mass flow in the phloem
Auxin seems to be involved in determining whether a plant grows upwards or whether it
branches sideways. When the apical bud is actively growing, it tends to stop lateral buds
from growing. This is called apical dominance. The plant grows upwards
rather than branching out sideways.
However, if the apical bud is cut off, the lateral buds start to grow. It is thought
that removal of the apical bud causes the concentration of auxin in lateral buds to
decrease so the buds can now grow by cell division
and cell elongation / division / mitosis

Answer 128

A

(i) 1. carbon dioxide fixation ;
2. production of GP ;
3. ref. to rubisco ;

Answer 129

A

(ii) 1. reduction (of GP) / donates hydrogen ;

2. GP to TP

Answer 130

A

supplies, energy / phosphate ;
1. (to convert) GP to TP ;
2. (to) regenerate of RuBP

Answer 131

A

(ii) 1. ref. to voltage-gated sodium ion channels / ref. ligand gated channels ;
2. channels change shape (when, pd / voltage, changes) ;

open when, membrane depolarises / action potential arrives / neurotransmitter
binds to receptors ;

4. sodium ions flood in ; 
5. diffuses / down concentration gradient ;
6. channels close when membrane, repolarises / potential reaches +30mV ; 
7. ref. to sodium-potassium pump ;

Answer 132

A

to avoid inbreeding depression ;
hybrids have, higher yields / hybrid vigour ;
avoids expression of harmful recessive alleles ;
ref. to genetic uniformity ;
(which) results in easier, cultivation / harvest / etc

Answer 133

A

lipid releases most energy ;
1. because it has more, hydrogens / C-H bonds ;
2. per unit mass ;
3. hydrogens needed for, ATP production / chemiosmosis

Answer 134

A

1 carry blood to, cardiac/heart, muscle/tissue/cells ;

2 supply oxygen ;

3 supply, nutrient/named nutrient ;

4 for, energy release/respiration ; R produce energy

Answer 135

A

1 less surface area ;

2 less absorption of light ;

3 less, photophosphorylation / light dependent reaction ;

4 less chemiosmosis ;

5 (due to) smaller thylakoid space or reduced proton gradient ;

6 less ATP (produced) ;

7 less reduced NADP (produced) ;

8 light-independent reaction / Calvin cycle, slows down ;

9 less carbon dioxide, fixed / combined with PEP ; R uptake

Answer 136

A

1 reduced, NAD/FAD ;

2 dehydrogenase enzymes ;

3 release hydrogen ; A H R H2/H
+

4 hydrogen splits into proton and electron ;

5 electrons flow down, ETC/AW ;

6 energy released ;

7 protons pumped (across inner membrane/from matrix) ;

8 into intermembrane space ;

9 proton gradient ;

10 protons pass through, ATP synthase/stalked particle ;

11 oxygen final, hydrogen/proton, acceptor ;

Answer 137

A

1 glycolysis, does not occur in mitochondrion/only occurs in cytosol or cytoplasm ;

2 pyruvate produced in glycolysis ;

3 pyruvate can enter mitochondrion/glucose cannot enter mitochondrion ;

4 carbon dioxide produced/decarboxylation, in, Krebs/link reaction

Answer 138

A

1 closely packed to absorb maximum light ;

2 vertical/at right angles to surface of leaf to reduce number of cross walls ;

3 large vacuole pushes chloroplasts to edge of cell ;

4 chloroplasts at edge short diffusion path for carbon dioxide ;

5 chloroplasts at edge to absorb maximum light ;

6 large number of chloroplasts to absorb maximum light ;

7 cylindrical cells or air spaces to circulate gases/provide a reservoir of CO2 ;

8 large surface area for diffusion of gases ;

9 moist cell surfaces for diffusion of gases ;

10 cell walls thin for maximum light penetration/diffusion of gases ;

11 chloroplasts can move towards light ;

12 chloroplasts can move away from high light intensity to avoid damage ;

Answer 139

A

) 13 Calvin cycle/stroma ;

14 carbon dioxide fixed by RuBP ;

15 rubisco ;

16 2 molecules of GP formed ; A PGA

17 (GP) forms TP ; A GALP/PGAL

18 use of ATP ;

19 use of, reduced NADP /NADPH ;

20 from light dependent stage ;

21 some TP forms, hexose/sucrose/starch/cellulose/glycerol ;

22 some TP converted to acetyl CoA ;

23 some TP used to regenerate RuBP ;

24 using ATP ;

allow either mp 18 or mp 24

marks can be awarded on a diagram

Answer 140

A

1 renal/Bowman’s, capsule ;

2 ref. podocytes ;

3 (proximal convoluted tubule/distal convoluted tubule/capsule) in cortex ;

4 proximal convoluted tubule ;

5 loop of Henle ;

6 (loop) in medulla ;

7 distal convoluted tubule ;

8 afferent arteriole ;

9 glomerulus ;

10 efferent arteriole ;

11 capillary network around/proximal convoluted tubule/loop/distal convoluted tubule ;

12 collecting duct ;

Answer 141

A

13 endothelium of, blood capillaries/glomerulus ;

14 more/large, gaps between endothelial cells ;

15 podocytes ;

16 large gaps between podocytes/filtration slits ;

17 basement membrane, selective barrier/acts as a filter ;

18 prevents, large protein/RMM > 68 000, passing through ;

19 no cells pass through ;

20 named molecule which is filtered ; e.g. urea/water/glucose/uric acid/creatinine/
Na + /K
+
/Cl

;

21 high, blood/hydrostatic, pressure in glomerulus ;

22 afferent arteriole wider than efferent arteriole ;

23 lower pressure in, renal/Bowman’s, capsule ;

24 fluid forced into capsule/ultrafiltration

Answer 142

A

β cells detect glucose levels or no detection of blood glucose conc. ;
2. β cells secrete insulin or no insulin released ;
3. when blood glucose concentration rises or when blood glucose concentration rises ;
4. (insulin causes) muscle cells / adipose
tissue / liver cells
or muscle cells / adipose tissue / liver cells ;
5. to increase uptake of glucose from blood
/ increased membrane permeability to
glucose
or do not take up excess glucose ;
6. (insulin causes liver cells) to convert
glucose to glycogen
or glucose not converted to glycogen (by
liver cells)
;
7. (insulin causes liver cells) to increase
respiration of glucose
or rate of respiration of glucose does not
increase
;
8. (if no β cells) no control of blood glucose
levels / AW
or no control of blood glucose levels / AW

Answer 143

A

insulates axon (membrane) ;
depolarisation occurs only at nodes (of Ranvier) / AW ;
local circuits ;
saltatory conduction / AW ;
speeds transmission of, action potential / impulse ;
AVP ; e.g. speed increases up to 50 times / 100ms

Answer 144

A

i) (converted to) glycogen / lipid ;

(used in) glycolysis / respiration

Answer 145

A

cannot pass through phospholipid bilayer ;
1. too big to fit through (glucose’s) protein channel ;
2. no specific transport protein ;
3. AVP ; e.g. used up as soon as it is made

Answer 146

A

endocrine
1. hormones ;
2. chemical messengers ; A chemicals that transfer information
3. ductless glands / (released) into blood ;
4. target, organs / cells ;
5. ref. receptors on cell membranes ;
6. example of named hormone and effect ;
nervous
7. impulses/ action potentials ; R electrical, signals / current
8. along, axon / neurones / nerve fibres ; R nerves R across
9. synapse (with target) / neuromuscular junction ;
10. ref. receptor / sensory neurones ;
11. ref. effector / motor neurones ;
differences – endocrine
12. slow effect / ora ;
13. long lasting effect / ora ;
14. widespread effect / ora ;
15. AVP ; e.g. extra detail of synapse / hormone changes triggered within cells

Answer 147

A

) 1. photosystem I (PI) and photosystem II (PII) involved ;
2. light harvesting clusters ;
3. light absorbed by accessory pigments ;
4. primary pigment is chlorophyll a ;
5. energy passed to, primary pigment / chlorophyll a ;
6. electrons, excited / raised to higher energy level ;
7. (electrons) taken up by electron acceptor ;
8. (electrons) pass down electron carrier chain (to produce ATP) ;
9. PII has (water splitting) enzyme ;
10. water split into protons, electrons and oxygen ; A equation
11. photolysis ;
12. electrons from PII pass to PI / electrons from water pass to PII ;
13. to replace those lost ; give either in relation to PI or PII
14. protons and electrons combine with NADP (to produce reduced NADP) ;
can award these marking points from a diagram

Answer 148

A

) 15. RuBP combines with carbon dioxide ;

rubisco ;
forms unstable 6C compound ;
produces two molecules of, GP / PGA ;
GP / PGA, converted to TP ;
by reduced NADP and ATP ;
from light dependent stage ;
TP used to regenerate RuBP ;
using ATP ;
TP can form, hexose / fatty acids / acetyl CoA

Answer 149

A

26

°C optimum temperature for, rubisco / enzyme of Calvin cycle ;

(at just over 40

°C) enzymes / rubisco, denatured ;

so less carbon dioxide fixed ;
reduction in Calvin cycle / AW ;
increased rate of transpiration / AW ;
so stomata close ;
less carbon dioxide uptake ;
oxygen more likely to combine with rubisco ;
so increased photorespiration ;

Answer 150

A

) 1. reduced, NAD / FAD ;

passed to ETC ;
inner membrane / cristae ;
hydrogen released (from reduced, NAD / FAD) ; R H2
split into electrons and protons ;
electrons pass along, carriers / cytochromes ;
ref. energy gradient ;
energy released pumps protons into intermembrane space ;
proton gradient ;
protons pass through (protein) channels ;
ATP synthase / stalked particles ;
(ATP produced from) ADP and inorganic phosphate ;
electron transferred to oxygen ;
addition of proton (to oxygen) to form water / (oxygen) reduced to water

Answer 151

A

mechanisms

active transport ; A actively pumped / uses ATP
Na+ , out of pct cells / into blood ;
(sets up) Na+ ion gradient ;
facilitated diffusion ;
using protein carrier ; A transport protein
cotransport (from lumen to pct cell);
of, glucose / amino acids / ions;
osmosis ;
down water potential gradient ;
diffusion (in correct context) ;
down a concentration gradient ; max 7

adaptations

microvilli ; A brush border
many mitochondria ;
PMT
Page 16 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9700 41

tight junctions ;
folded, basal membrane / described ;
many, transport proteins / cotransporters / pumps;
AVP ; e.g. many aquaporins

Answer 152

A

) many of these mps can be given from a labelled diagram

(outer) cortex ;
medulla ;
pelvis ;
renal artery ;
renal vein ;
nephron / (kidney) tubule ;
renal capsule / proximal convoluted tubule (pct) / distal convoluted tubule (dct), in cortex ;
loop of Henle / collecting duct (cd), in medulla ;
glomerulus ;
afferent & efferent arterioles;
capillary network, surrounds tubule / in medulla ;

Answer 153

A

(iii) reduces/donates hydrogen ; A H/hydrogen atoms/H+ AND e– R H+ / H2

GP to TP ; A PGA to PGAL
[

Answer 154

A

production of tTA causes production of more tTA/AW

Answer 155

A

ATP is made, in the electron transport chain/by oxidative phosphorylation;
oxygen is the final electron acceptor;
in the, inner membrane of the mitochondrion/cristae;
transfer of electron (between electron carriers) provides energy;
energy used to pump hydrogen ions (into intermembrane space);
creates proton gradient;
diffusion of hydrogen ions down their electrochemical gradient causes ATP to be synthesised;
ref. chemiosmosis/ATP synthase/stalked particles;
idea that if less oxygen (consumed/available) then fewer electrons transferred along the chain;

Answer 156

A

oxygen consumed = oxygen inhaled – oxygen exhaled;

measure oxygen consumption at rest (x) and after exercise stops (y);
extra oxygen consumed/oxygen debt = y – x;
measure mass of lizard;

Answer 157

A

light energy absorbed by chlorophyll; A photosystems/pigments
electron, excited/raised to higher energy level;
(electron) emitted by chlorophyll; A photosystems/pigments
passes to electron, acceptor/carrier;
passes along, chain of electron carriers/ETC/Electron Transfer Chain;
energy released used to pump protons; I ATP production here
into thylakoid space;
thylakoid membrane impermeable to protons;
proton gradient forms;
protons move down gradient;
through/using, ATP synthase/ATP synthetase; R ATPase
enzyme rotates;
ATP produced from ADP and Pi;

Answer 158

A

anaerobic respiration ;

substrate level phosphorylation (in glycolysis);

at triose phosphate pyruvate step ;

(net) gain of 2ATP (per glucose) ; A 2 used and 4 produced

pyruvate, reduced

/

gains hydrogens (from reduced NAD) ;

forming lactate ;

NAD regenerated

/

NADH2 re-oxidised ;

this allows glycolysis to continue

Answer 159

A

α cells / β cells / islets / B, secrete, hormones / glucagon / insulin ;
into the blood / not into a duct ;

Answer 160

A

1 increases permeability of membrane to glucose / increases glucose uptake ;
2 increases respiration of glucose ;
3 (increases), conversion of glucose to glycogen / glycogenesis ;
4 (increases) protein / fat, synthesis ;

Answer 161

A

they contain chlorophyll ;

green / blue green / yellow green, light reflected ;

Answer 162

A

1 light not limiting ; 
2 much, ATP / reduced NADP, available ; 
3 CO2 is the limiting factor ; 
4 because low concentration CO2 (in atmosphere) ; 
5 more CO2 combines with RuBP ; 
6 ref. rubisco ; 
7 Calvin cycle / light independent stage ; 
8 GP to TP ; 
9 more hexose produced ; 
10 ref. fate of hexose

Answer 163

A

in cytoplasm 19 NAD, becomes reduced / accepts H ;
20 during glycolysis ;

in plants 21 pyruvate converted to ethanal ;
22 ethanal reduced ;
23 by reduced NAD ;
24 ethanol formed ;

in animals 25 pyruvate converted to lactate ;
26 by reduced NAD ;
27 in, liver / muscles ;
28 allows glycolysis to continue ;

Answer 164

A

1 increase in rate of respiration ;

2 kinetic energy increases / more enzyme-substrate complexes / enzyme activity increases ;

3 effects of too high a rise in temperature ; e.g. denaturation of enzymes

4 AVP ; e.g. Q10 = 2

Answer 165

A

) when acetylcholinesterase is inhibited 1 acetylcholine remains attached to receptors (on post-synaptic membrane) ;

2 sodium channels on post-synaptic (membrane) remain open ;

3 membrane remains depolarised ;

4 action potentials / nerve impulses, continue to be produced ;

Answer 166

A

1 permanently ;

2 binds with / blocks, active site ;

3 binds with, another part of enzyme / allosteric site ;

4 change (shape) of active site ;

Answer 167

A

1 ref. ABA absence ;

2 H+ transported out of guard cells, actively / using ATP ;

3 low H+ conc / negative charge, inside cell ;

4 K+ channels open / K+ diffuses into cell ;

5 water potential of cell falls ; A decrease in solute potential

6 water moves into cell by osmosis ;

7 volume of guard cells increase / turgor increases ;

guard cells: 8 have hoops of cellulose microfibrils which ensure increase in length rather than diameter ;

9 have ends that are joined together ;

10 have, thicker inner walls / thinner outer walls ;

11 curve apart / bend, (to open stoma) ;

Answer 168

A

) hydrogen carrier ;

GP, reduced / hydrogen added ; R H2

to, TP / 3 carbon sugar ;

uses ATP ;

Answer 169

A

) 17 ADH affects collecting duct ;

18 binds to receptor on membrane ;

19 increase membrane permeability (to water) / more water channels ;

20 ref. enzyme controlled reactions ;

21 produces (active) phosphorylase ;

22 (which causes) vesicles with, water channels / aquaporins ; must be linked to 23

23 to, move to / fuse with, (plasma) membrane ;

24 more water flows out of collecting duct ;

25 down / along, water potential gradient ;

26 (then) into blood ;

27 urine (more) concentrated / small volume of urine ;

28 ref. negative feedback ;

29 AVP ; e.g. role of loop of Henle in creating water potential gradient movement of urea increases water potential gradient [7 max]

Answer 170

A

1 selective reabsorption ;

2 (pct cells have) villi / microvilli / large surface area ;

3 (pct cells have) many mitochondria ;

4 Na+ leave pct cells ;

5 by active transport ;

6 Na+ concentration falls in (pct) cells / Na+ concentration gradient ;

7 Na+ (diffuse) from lumen into (pct) cells ;

8 through, transporter / carrier, proteins ; ignore channel proteins

9 cotransport ;

10 of, glucose / amino acids / vitamins / chloride ions ;

11 (from pct cells) into intercellular fluid ; linked to 10

12 (then) diffusion into blood ; linked to 10

13 (normally) all glucose reabsorbed ;

14 some water reabsorbed ;

15 some urea reabsorbed ;

16 AVP ; e.g. creatinine secreted into lumen

Answer 171

A

1 rubisco

/

enzymes, denatured

/

AW ;
2 less, photolysis

/

ATP produced

/

light-dependent stage

/

Calvin cycle ;
3 less carbon dioxide fixed ;

4 increase in transpiration ;

5 photorespiration

/

AW ;

6 stomata close ; 7 reduction in carbon dioxide uptake ;

8 loss of turgor

/

wilting ;
[

Answer 172

A

) 1 (Ca2+) released from sarcoplasmic reticulum ; 2 binds to troponin ; 3 (troponin) changes shape ; 4 tropomyosin is, displaced
/
AW ; 5 (myosin) binding sites exposed ; 6 myosin head now, binds
/
attaches
/
joins, to actin ; 7 AVP ; e.g. ref. myosin pulls actin

Answer 173

A

has genes that code for: mitochondrial proteins ; mitochondrial enzymes ; mitochondrial replication ; rRNA

Answer 174

A

oxygen

pyruvate

ADP

phosphate

/

Pi

fatty acids

Answer 175

A

carbon dioxide

ATP

water

Answer 176

A

max 3 from mp1–mp5 1 ETC / electron transport chain, stops ; 2 Krebs cycle
/
link reaction, stops ; 3 no proton gradient set up ; 4 no proton flow through ATP synthase ; 5 less
/
no, ATP produced ;

6 named muscle fails to contract ; e.g. heart

/

intercostals

Answer 177

A

) both have ribose (sugars) ; R ribulose ATP has 1, ribose
/
pentose
/
sugar, NAD has 2 ; I ref. to additional hexose both have, adenine
/
purine (base) ; I adenosine NAD has, nicotinamide
/
pyrimidine (base) ; ATP has 3 phosphates, NAD has 2

Answer 178

A

d) hydrogen, carrier

/

acceptor ; A gets reduced or gains H

/

H+ and electrons
I donates R H2

/

hydrogen molecules (acts as a) coenzyme ; A enables dehydrogenases to work ref. to glycolysis
/
respiration in anaerobic conditions ; A anaerobic respiration I aerobic

Answer 179

A

exocytosis

Answer 180

A

causes glucose uptake

/

increases permeability to glucose ; adds transport proteins to cell (surface) membrane ; A in sarcolemma A GLUT(4), proteins / channels / carriers more glucose respired
/
increase in respiration rate ; glucose converted to glycogen
/
glycogenesis

Answer 181

A

accept stimulates

/

stimulated, for activates

/

activated throughout 
  1 (adrenaline) receptor shape change ; 2 G-proteins activated ; A description of G protein releases (α) subunit 3 adenylyl cyclase activated ; A adenyl(ate) cyclase 4 cyclic AMP made ; 5 (cAMP is) second messenger ; 6 activates
 /
 phosphorylates, kinase ; 7 ref. to enzyme cascade
 /
 cascade of reactions ; 8 glycogenolysis
 /
 hydrolysis of glycogen, stimulated
 /
 AW ; A break down glycogen 9 AVP ; gluconeogenesis
 /
 ref. to glucose transport proteins  A description
 /
 glucose from, amino acids
 /
 lipids A GLUT(2) channels
 /
 carriers

Answer 182

A

only, stimulus

/

depolarisation

/

receptor potential

/

potential difference, that reaches threshold produces an action potential ; ora A -50mV for threshold A generator for receptor

idea that the action potential is the same size no matter how strong the stimulus ; ref. to all-or-nothing (law) ; I all-and-nothing

Answer 183

A

1 pyruvate formed by glycolysis ; 2 reduced NAD formed by glycolysis ; 3 pyruvate decarboxylated
/
AW ; 4 ethanal produced ; 5 pyruvate decarboxylase ; 6 ethanal is, hydrogen acceptor
/
reduced ; A gains H or gains H+ and e– 7 from
/
by, reduced NAD ; 8 ethanol formed ; 9 ethanol
/
alcohol, dehydrogenase ; 10 not reversible reaction ; 11 NAD, regenerated
/
can now accept hydrogen atoms ; A reduced NAD oxidised 12 so glycolysis can continue ;

Answer 184

A

(i) have chloroplasts

/

varying thickness of (cell) walls

/

no plasmodesmata

Answer 185

A

A sensory receptor cell responds to a stimulus by opening ion chaneels. in
its cell surface membrane. Sodium ions flood into the cell causing the membrane to become
depolarised. This is called the generator potential. If this potential is
large enough to reach a threshold then an action potential is transmitted to the
central nervous system. An increase in the strength of the stimulus will result in an increase in
thefrequency of action potentials transmitted.

Answer 186

A

action potential stimulates neighbouring area of membrane ; AW

Na+, moves sideways

/

attracted to areas at resting potential ; A local circuit

causes, Na+ ion channels to open

/

2nd depolarisation ;

(transmission) in one direction due to, hyperpolarisation

/

refractory period ;

myelin sheath

/

Schwann cell ;

sheath insulates, axon

/

dendron

/

neurone ;

depolarisation

/

action potential, only at nodes of Ranvier

/

unmyelinated part ; ora

saltatory conduction

/

action potential ‘jumps’ from node to node ;

Answer 187

A

ATP is made, in the electron transport chain/by oxidative phosphorylation;
oxygen is the final electron acceptor;
in the, inner membrane of the mitochondrion/cristae;
transfer of electron (between electron carriers) provides energy;
energy used to pump hydrogen ions (into intermembrane space);
creates proton gradient;
diffusion of hydrogen ions down their electrochemical gradient causes ATP to be synthesised;
ref. chemiosmosis/ATP synthase/stalked particles;
idea that if less oxygen (consumed/available) then fewer electrons transferred along the chain;

Answer 188

A

mechanisms

active transport ; A actively pumped / uses ATP
Na+ , out of pct cells / into blood ;
(sets up) Na+ ion gradient ;
facilitated diffusion ;
using protein carrier ; A transport protein
cotransport (from lumen to pct cell);
of, glucose / amino acids / ions;
osmosis ;
down water potential gradient ;
diffusion (in correct context) ;
down a concentration gradient ; max 7

adaptations

microvilli ; A brush border
many mitochondria ;
PMT 25. tight junctions ;
folded, basal membrane / described ;
many, transport proteins / cotransporters / pumps;
AVP ; e.g. many aquaporins

Answer 189

A

(outer) cortex ;
medulla ;
pelvis ;
renal artery ;
renal vein ;
nephron / (kidney) tubule ;
renal capsule / proximal convoluted tubule (pct) / distal convoluted tubule (dct), in cortex ;
loop of Henle / collecting duct (cd), in medulla ;
glomerulus ;
afferent & efferent arterioles;
capillary network, surrounds tubule / in medulla ;

Answer 190

A

hydrogens split into protons and electrons ;
electrons pass along ETC ;
energy released used to pump protons ;
(from matrix) to intermembrane space ;
inner membrane impermeable to protons ;
proton gradient forms ;
protons move down gradient ;
through ATP, synthase / ATP synthetase ; R ATPase
enzyme rotates ;
ATP produced ;

Answer 191

A

(photosynthetic pigments) arranged in light harvesting clusters ;
primary pigments / chlorophyll a ;
at reaction centre ;
P700 / Pl, absorbs light at 700nm ;
accessory pigments / chlorophyll b / carotenoids ;
surround, primary pigment / reaction centre / chlorophyll a ;
absorb light ;
pass energy to, primary pigment / reaction centre / chlorophyll a ;
(light absorbed results in) electron excited / AW ;
emitted from, chlorophyll / primary pigment / reaction centre ;
passes to electron, acceptor / carrier ;
(electron) passes along, chain of electron carriers / ETC ;
ATP (synthesis) ;
electron returns to, P700 / Pl ;

Answer 192

A

) 15. photolysis of water ;
16. releases H + ; R H / hydrogen atoms
17. by, P680 / PII ;
18. e released from, P700 / PI ;
19. e (from PI) and H +
combine with NADP ;
20. used in Calvin cycle ;
21. reduces, GP / PGA ;
22. to TP ;
23. ATP used (during reduction of GP) ;
24. NADP, regenerated / oxidised ; [7 max]

Answer 193

A

1 inner mitochondrial membrane/cristae ;

2 dehydrogenase enzymes ;

3 release hydrogen ;

4 hydrogen splits into protons and electrons ;

5 electrons flow down, ETC/Electron Transfer Chain/AW ;

6 energy released ;

7 protons pumped across (inner membrane) ;

8 into intermembrane space ;

9 proton gradient ;

10 protons pass through, ATP synthase/stalked particles ;

11 ATP formed ; linked to 10

12 oxygen (final), hydrogen/proton and electron, acceptor

Answer 194

A

1 pyruvate converted to ethanal ;

2 ethanal reduced ;

3 by reduced NAD ;

4 NAD, oxidised/regenerated ;

5 allows glycolysis to continue ;

6 ethanal dehydrogenase ;

7 ethanol formed ;

8 prevents H + from lowering pH

Answer 195

A

1 nucleus in cell body ;

2 (long) dendron ; R plural

3 (shorter) axon ;

4 many mitochondria (in cell body) ;

5 many RER/nissl’s granules, (in cell body) ;

6 synaptic knobs ;

7 detail of synaptic knob ;

8 (terminal) dendrites ;

9 Schwann cells ;

10 detail of myelin sheath ;

11 nodes of Ranvier ;

accept points on labelled diagram

Answer 196

A

1 arranged in light harvesting, clusters/system ;

2 primary pigments/chlorophyll a ;

3 at reaction centre ;

4 P700/P1, absorbs at 700(nm) ;

5 P680/P11, absorbs at 680(nm) ;

6 accessory pigments/chlorophyll b/carotenoids, surround, primary pigment/reaction
centre/ chlorophyll a ;

7 pass energy to, primary pigment/reaction centre/chlorophyll a ;

8 P700 / PI, involved in cyclic photophosphorylation ;

9 (light absorbed results in) electron excited/AW ;

10 emitted from, chlorophyll/photosystem ;

11 flows along, chain of electron carriers/ETC ;

12 ATP synthesis ;

13 electron returns to, P700/P1 ;

Answer 197

A

accept ABA for abscisic acid
1. stress hormone ;
2. plant secretes ABA in, high temperatures / dry conditions ;
3. ABA binds to receptors ;
4. on plasma membranes of guard cells ;
5. inhibits proton pump / H +
not pumped out of cell ;
6. high H + conc / positive charge, inside cell ;
7. K + diffuses out of cell ;
8. water potential of cell increases ; A increase in solute potential
9. water moves out of cell by osmosis ;
10. volume of guard cells decreases ;
11. guard cells become flaccid ;
12. response very fast ;

Answer 198

A

) 13. (barley) seed is, dormant / metabolically inactive ;

seed absorbs water ;
embryo produces gibberellin ;
gibberellin stimulates aleurone layer ;
to produce amylase ;
amylase hydrolyses starch ;
in endosperm ;
to maltose / glucose ;
embryo uses sugars for respiration ;
energy used for growth ;
gibberellins affect, gene / transcription of mRNA, coding for amylase ; [7 max]

Answer 199

A

v1. (homeostasis is) maintenance of, constant / stable, internal environment ;
2. irrespective of changes in external environment ;
3. negative feedback ;
4. receptor /appropriate named cell, detects change in, parameter / blood glucose concentration ;
5. (receptors are) β / α , cells ;
6. in, Islets of Langerhans / pancreas ;
7. insulin / glucagon, released ;
8. action taken by effector / correct action described (liver / muscle, cell) ;
9. restoration of, norm / set point / AW ;
10. ref. fluctuation around the norm ; [6 max]

Answer 200

A

endocrine 11. hormones ;

chemical messengers ; A chemicals that transfer information
ductless glands / (released) into blood ;
target, organs / cells ;
ref. receptors on cell membranes ;
example of named hormone and effect ;

nervous 17. impulses / action potentials ; R electrical, signals / current

along, neurones ; R nerves
synapse (with target) / neuromuscular junction ;
ref. receptor / effector or sensory / motor, neurones ;

differences – endocrine 21. slow effect / ora ;

long lasting effect / ora ;
widespread effect / ora ;
AVP ; e.g. extra detail of synapse

Answer 201

A

ethene (in plant);
stimulates production of gibberellin;
gibberellin stimulates, cell division / cell elongation / increase in stem length;
leaves / flowers, above water;
(so) photosynthesis can occur;
(so) sexual reproduction / pollination, can occur;
aerenchyma / description;
assists gas diffusion (within plant);
air can be trapped by specialised underwater leaves;
(submerged parts of plant) carry out anaerobic respiration;
produce ethanol;
can tolerate high concentrations of ethanol;
produce a lot of ethanol dehydrogenase

Answer 202

A

3 – 10 µm (diameter);
double membrane;
ground substance / stroma;
contains enzymes / named enzyme, e.g. rubisco;
also, sugars / lipids / starch;
70S / AW, ribosomes;
circular DNA;
internal membrane system / fluid-filled sacs / thylakoids; A flattened sacs
grana are stacks of thylakoids;
(grana) membranes hold, photosynthetic pigments / ATP synthase / ETC

Answer 203

A

produce ATP / provide energy;
for active transport of Na+;
out (of cell);

Answer 204

A

mark first two answers any named ion / mineral ions;

vitamins;

amino acids;

glucose;

some urea;

Answer 205

A

fluid can pass through glomerular capillaries because (max 3) 1. fenestrations in capillary endothelium; A hole / pores / gaps

basement membrane acts as a filter;
no substances >68 000 MM can get through;
no cells can get through;

fluid can pass through podocytes because 5. have, projections / AW;

gaps (between projections); A filtration slits

Answer 206

A

(when pump stops working), resting potential not maintained or pump usually maintains the resting potential;
(during resting potential) membrane polarised or positive charge outside (neurone) / negative charge inside (neurone) / -70mV inside neurone relative to outside / potential difference across membrane;
(when pump stops working), ions (only) move by diffusion;
Na+ into the neurone;
outward diffusion of K+ is limited / K+ stay in neurone;
ref. non voltage-gated channels;
(eventually) inside of the neurone, becomes less negative / contains (relatively) more positive ions or there is a reduced potential difference across the membrane;

voltage gated (calcium) channels open;

(calcium ions move in) by diffusion / move down their concentration gradient; [2]

Answer 207

A

final electron acceptor / accepts electron from last carrier;
so carrier can be reduced again;
so electrons can keep flowing (along ETC) / so ETC can continue to work;
(oxygen) combines with H+ to form water;

Answer 208

A

(electron comes from) hydrogen (atom); R H+ / H2
(from) reduced NAD / reduced FAD;
(from) dehydrogenation / oxidation, reactions;
(from substances in) Krebs cycle / link reaction / glycolysis;
in, matrix of mitochondrion / cytoplasm

Answer 209

A

inner membrane / crista(e);

Answer 210

A

(iii) respiration uses oxygen;

Answer 211

A

(c) compresses nerve ;

damages, myelin sheaths

/

Schwann cells ;

prevents, setting up of local circuits

/

saltatory conduction ;

stops Na+

/

K+ pumps from working ;

blocks blood supply;

qualified ; e.g. effect on, oxygen supply

/

glucose supply

/

ATP production

AVP ; e.g. may stop ion channels opening

Answer 212

A

affects collecting duct, (cells

/

wall) ; A distal convoluted tubule cells

binds to receptors on cell surface membranes ;

activates series of enzyme controlled reactions ;

(phosphorylase causes), vesicles

/

aquaporins, to move to cell surface membrane
(on lumen side) ;

vesicles

/

aquaporins, fuse with cell surface membrane ;

cells

/

wall, more permeable to water ;

water moves out of lumen (of collecting duct) ;

down water potential gradient ; [max 5]

produce, a lot of urine

/

dilute urine ;

dehydration

/

thirsty ;

cramps

/

loss of salts ;

Answer 213

A

for one mark ; any 2 from urine sweat water vapour (from exhaled air) faeces bleeding tears [max 1]

Answer 214

A

posterior pituitary

Answer 215

A

DNA codes for, proteins

/

polypeptides

/

enzymes ;

one example of protein or enzyme ; e.g. rubisco

/

electron acceptor

/

ATP synthase

/

transport

ref. transcription

/

mRNA ;

Answer 216

A

lipids 1 more C-H bonds

/

more reduced

/

more hydrogen ;

2 produces more reduced NAD ;

3 produces more ATP per, gram

/

unit mass ;

4 more, aerobic respiration

/

oxidative phosphorylation

/

chemiosmosis ;

5 fats only broken down aerobically ;

Answer 217

A

1 active transport ;

2 ref. to sodium potassium pump ;

3 sodium ions out and potassium ions in ;

4 against their, concentration

/

electrochemical, gradient ;

5 ref. to, ion diffusion

/

ion leakage ; [max 3]

Answer 218

A

1 carbon dioxide ; A CO2

2 ATP ;

3 reduced NADP ; mp 2 and mp3 in either order

4 acetyl CoA ; [4]

Answer 219

A

to absorb, more

/

maximum, light ;

to avoid damage by high light intensities ; [2]

Answer 220

A

1 oxaloacetate accepts, acetate

/

acetyl group

/

2C fragment ;
2 to form citrate ; 3 4C to 6C ; 4 decarboxylation ; 5 CO2 released ; 6 dehydrogenation
/
oxidation ; 7 reduced NAD produced ; 8 reduced FAD produced ; 9 ATP produced ; 10 substrate-linked
/
substrate-level, phosphorylation ; 11 ref. to intermediate compounds ; 12 enzyme-catalysed reactions ; 13 oxaloacetate regenerated ;

Answer 221

A

1 lysis

/

splitting

/

break down, of glucose ; R sugar splitting  2 (glucose) phosphorylated by ATP ; 3 raises energy level
 /
 to activate the reaction
 /
 reduces activation energy
 /

to make it reactive ; 4 fructose (1,6) bisphosphate ; 5 (breaks down to) two, triose phosphate
/
TP ; 6 hydrogen removed by NAD ; A triose phosphate oxidised by NAD 7 reduced NAD formed ; 8 pyruvate produced ; 9 small yield of ATP ;

Answer 222

A

) combines with, acetyl group

/

acetate ;
ref. to link reaction ; (delivers, acetyl group

/

acetate) to the Krebs cycle ;
(acetyl group

/

acetate) combines with oxaloacetate ; R Acetyl CoA combines with oxaloacetate

Answer 223

A

describe 1 increased temperature increases the rate of photosynthesis at high light intensities ; 2 increased temperature has little effect at low light intensity ;

explain 3 increased kinetic energy ; 4 (leads to) increased, no. of collisions

/

(rate of) enzyme activity

/

ESCs

/

enzyme-subtrate
complexes ; 5 (high light intensity) temperature is the limiting factor ; 6 (low light intensity) light intensity is the limiting factor ;

Answer 224

A

passes energy to, chlorophyll a

/

primary pigment

/

reaction centre ;
may absorb light wavelengths that, chlorophyll a

/

primary pigment

/

reaction centre, does not
absorb ; forms part of, light-harvesting cluster of pigments

/

photosystem

/

antenna complex ;

Answer 225

A

deamination

/

amine group removed ; A amino

/

NH2
ammonia

/

NH3, formed ; combined with carbon dioxide ; urea cycle ; A ornithine cycle

Answer 226

A

1 (diameter of lumen of) afferent arteriole wider than efferent arteriole ;  2 (leads to) high, blood
 /
 hydrostatic, pressure ; 3 plasma
 /
 fluid, passes through, gaps
 /
 fenestrations, between   endothelial cells (of capillaries) ; 4 ref. to basement membrane acts as a, filter
 /
 selective barrier ; 5 red cells
 /
 large proteins
 /
 molecules greater than 68
 000(MM), cannot pass through ; 6 podocytes qualified ; 7 (filtrate) passes into (renal) capsule ;

Answer 227

A

loop of collecting duct

Henle ;

Answer 228

A

collecting duct

distal convoluted tubule

Answer 229

A

ensure one-way transmission ;  allow interconnection of nerve pathways
 /
 AW ; involved in, memory
 /
 learning ; idea of filtering out, less frequent impulses
 /
 low level stimuli
 /
 AW

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