This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitamins and Minerals, Subject name: Biochemistry
[{'content': 'Absence of which of the following enzyme in humans is responsible for the inability to synthesize ascorbic acid? \nSelect and explain. \nA. L-Glucuronic acid oxidase, B. L-Gulonic acid reductase, C. L-Gulonolactone oxidase, D. L-Gulonolactone reductase', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Uronic acid pathway is an alternate pathway for oxidation of glucose without ATP formation. Fig: Uronic acid pathway An intermediate (L-gluconate) of this pathway can be used for the synthesis of ascorbic acid in plants by enzyme L-gulonolactone oxidase. However, In human beings and other primates, as well as guinea pigs, bats, and some birds and fishes, ascorbic acid cannot be synthesized because of the absence of L-Gulonolactone oxidase.', 'role': 'assistant'}]