- Many animals have a gene that codes for L‑gulonolactone oxidase (GULO), a key enzyme in the biosynthesis of ascorbic acid (vitamin C). The graphs show the presence of ascorbic acid in rats’ urine after the injection of the lactones gulono, galactono, mannono and altrono.
(a) Determine with a reason which lactone cannot be used in the synthesis of ascorbic acid in rats. [2]
(b) Explain the need in humans to include ascorbic acid in the diet. [2]