A-LevelBiologyEnergy and respiration9700/41 · May/June 2023 · Q97 Marks
Many factors affect the rate of cellular respiration.
- (a)Pyruvate carboxylase (PC) deficiency is a rare disease. The rate of respiration in the cells of a person with PC deficiency is much lower than normal. The passage describes the occurrence of PC deficiency in human populations. Complete the passage by using the most appropriate scientific terms. PC deficiency affects one in 250000 people. A person either has the disease or does not, so there are no intermediate forms of the disease. PC deficiency is caused by a genetic mutation in one gene. Whether a person develops the disease is not influenced by factors. The distribution of PC deficiency in human populations shows variation.[2]
- (b)Coenzymes are important in aerobic respiration. Outline the roles of named coenzymes in aerobic respiration.[5]
Mark scheme
Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.
- 1 environmental ;
- 2 discontinuous ;
- coenzyme A: 1 accepts / binds to / transfers, acetyl (group) ;
- 2 acetyl / 2C fragment, + oxaloacetate → citrate ;
- 3 (joins) link reaction and Krebs cycle ;
- NAD/FAD: 4 transfer / transport / carry / accept / reduced by, H+ and e¯ / H (atoms) / hydrogen (atoms) ;
- 5 ref. dehydrogenation (reactions) / dehydrogenase (enzymes) ;
- 6 transport, to cristae / to inner mitochondrial membrane / to ETC / for oxidative phosphorylation ;
- 7 NAD (accepts H) in glycolysis and link reaction and Krebs cycle ;
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