The enzyme alanine transaminase (ALT) is found in the liver. The function of ALT is to convert the amino acid α-ketoglutarate into another amino acid, glutamate.

Mark scheme

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

1. [1] idea of shortage of, glutamate / an amino acid, in diet;
2. [2] any two from:
3. 1 uncontrolled mitosis / continuous cell cycle / cell cycle checkpoints not controlled ;
4. 2 abnormal mass of cells formed;
5. 3 no programmed cell death / no apoptosis / cells immortal ;
6. 4 AVP; e.g. mutation of, tumour suppressor gene / (proto)oncogene
7. [1] osmoreceptors in hypothalamus ;
8. [5] any five from:
9. 1 (ADH) secreted / released, into blood by posterior pituitary;
10. 2 binds to receptors on cell surface membranes ;
11. 3 of collecting duct cells ;
12. 4 enzyme cascade ;
13. 5 vesicles with aquaporins move towards (cell surface) membrane;
14. 6 add aquaporins to (cell surface) membrane ;
15. 7 water moves from collecting duct into blood, down a water potential gradient / by osmosis ;
16. 8 water potential of blood rises ;