A-LevelBiologyEnergy and respiration9700/43 · May/June 2020 · Q716 Marks

Fig. 7.1 shows part of the process of respiration in a mitochondrion. [Figure 7.1] With reference to Fig. 7.1, name: area A process B substance C

(a)(i)Fig. 7.1 shows part of the process of respiration in a mitochondrion. [Figure 7.1] With reference to Fig. 7.1, name: area A process B substance C[3]
(a)(ii)State the type of chemical compound that is represented by D.[1]
(a)(iii)State the process by which ATP can be synthesised directly during glycolysis or the Krebs cycle.[1]
(b)(i)The elephant seal, Mirounga angustirostris, spends most of its life in the ocean. Fig. 7.2 is an elephant seal. [Figure 7.2] Elephant seals can stay underwater for up to two hours. During this time, respiration continues. Fig. 7.3 shows the mass of blood in the body, as a percentage of total body mass, for the elephant seal and for three other mammals. [Figure 7.3] Fig. 7.3 shows that elephant seals have a higher mass of blood as a percentage of total body mass than humans. Calculate how many times greater this figure is for elephant seals compared to humans. Show your working and write your answer to two decimal places.[2]
(b)(ii)Suggest why an elephant seal needs such a large mass of blood as a percentage of total body mass.[2]
(c)Elephant seals have a very thick layer of adipose tissue under their skin. Adipose cells are rich in fat molecules. Suggest why 1g of fat will produce more ATP than 1g of carbohydrate as a respiratory substrate in aerobic respiration.[2]
(d)(i)Adipose tissue plays an important role in thermoregulation in elephant seals. State the role of adipose tissue in thermoregulation.[1]
(d)(ii)The hypothalamus in the brain is the control centre for thermoregulation. Outline how a change in temperature of the external environment results in an impulse arriving at the hypothalamus.[2]
(d)(iii)When the blood temperature of a mammal decreases, one response is that its body secretes more adrenaline. Suggest how an increase in adrenaline results in an increase in blood temperature.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.

[3] area A - intermembrane space;
process B - chemiosmosis / ATP synthesis ;
substance C – oxygen;
[1] enzyme / protein / polypeptide ;
[1] substrate-linked phosphorylation ;
[2] 22 (÷) 7;
3.14;
[2] any two from:
1 more red blood cells so more haemoglobin;
2 more haemoglobin to carry oxygen ;
3 more chance of aerobic respiration
or
less chance of anaerobic respiration;
[2] any two from:
1 (relatively) more C-H bonds ;
2 more reduced NAD produced ;
3 more hydrogen atoms to build up proton gradient;
4 more, chemiosmosis / oxidative phosphorylation;
[1] (thermal) insulation ;
[2] any two from:
1 (thermo)receptors in the skin detect change ;
2 ref. to threshold / all or nothing law ;
3 sensory neurone sends impulse (to hypothalamus) ;
[2] any two from:
1 increased, glycogenolysis / glucose available ;
2 (so) increased respiration;
3 (so) more heat energy generated (and transferred to blood) ;