A-LevelBiologyEnergy and respiration9700/42 · Oct/Nov 2021 · Q612 Marks

ATP is needed for many metabolic processes in living organisms. [Figure 6.1]

(a)(i)Describe the properties of ATP that make it suitable for its role as the universal energy currency.[4]
(a)(ii)Suggest why ATP is needed for protein synthesis.[2]
(b)(i)Complete Table 6.1 using the letters A to E from Fig. 6.1. Each letter may be used once, more than once, or not at all. Table 6.1 statement the site of the Krebs Cycle a phospholipid bilayer impermeable to H+ ions the site of translation letter[2]
(b)(ii)Assume that the mitochondrion in Fig. 6.1 is a cylinder. Calculate the surface area of this mitochondrion. Use the formula: Surface area of cylinder = 2πr² + 2πrh Show your working.[2]
(b)(iii)The inner membrane of the mitochondrion has a much larger surface area than the outer membrane because of the presence of cristae. Different cell types vary in the number of cristae present per mitochondrion. Cardiac muscle cells have mitochondria with a very large number of cristae. Suggest and explain why cardiac muscle cells have mitochondria with very large numbers of cristae.[2]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.

[1] (a)(i) water soluble ;
[1] (a)(i) (so) easily transported around the cell ;
[1] (a)(i) (ATP) loses, Pᵢ / phosphate group ;
[1] (a)(i) hydrolysed by ATPase / (ATP is) stable molecule ;
[1] (a)(i) to release energy, immediately / in small packets or ref. to 30.5 kJ (mol⁻¹);
[1] (a)(i) can be, recycled / regenerated or ATP ⇌ ADP + Pᵢ ;
[1] (a)(ii) unwinding DNA ;
[1] (a)(ii) activating (RNA) nucleotides ;
[1] (a)(ii) ref. to mRNA synthesis ;
[1] (a)(ii) peptide bond formation / joining amino acids ;
[1] (a)(ii) AVP; e.g. post translation modification / amino acid activation / moving ribosomes along mRNA / movement of mRNA from nucleus
[2] (b)(i) the site of the Krebs Cycle A a phospholipid bilayer impermeable to H+ ions E / D the site of translation C (all correct = 2 marks, 1 or 2 correct = 1 mark)
[1] (b)(ii) (2 × π× 0.36² ) + (2 × π × 0.36 × 5.25) or 2π × 0.36 (0.36 + 5.25) ;
[1] (b)(ii) 12.7 or 12.68 or 12.69; (accept 3.14 or π in workings)
[1] (b)(iii) (more cristae results in) more, ETC / (named) carrier proteins / ATP synthase ; or (more cristae results in) more, oxidative phosphorylation / chemiosmosis / ATP synthesis ;
[1] (b)(iii) (because) cardiac muscle must undergo continuous contractions / AW ;

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