Vitamin C process delays onset of deficiency. Ascorbic acid also converts (reversibly) to dehydroascorbate (DHA) and from that compound non-reversibly to 2,3-diketogluonate and then oxalate. These three compounds are also excreted via urine. Humans are better than guinea pigs at converting DHA back to ascorbate, and thus take much longer to become vitamin C deficient. Ascorbic acid performs numerous physiological functions in the human body. These functions include the synthesis of collagen, carnitine, and neurotransmitters; the synthesis and catabolism of tyrosine; and the metabolism of microsome. During biosynthesis ascorbate acts as a reducing agent, donating electrons and preventing oxidation to keep iron
Vitamin C -Galactose reacts with the enzyme -galactose dehydrogenase, whereby the lactone ring opens and forms again but with between the carbonyl on C1 and hydroxyl group on the C4, resulting in -galactonolactone. -Galactonolactone then reacts with the mitochondrial flavoenzyme -galactonolactone dehydrogenase. to produce ascorbic acid. -Ascorbic acid has a negative feedback on -galactose dehydrogenase in spinach. Ascorbic acid efflux by embryo of dicots plants is a well-established mechanism of iron reduction, and a step obligatory for iron uptake. All plants synthesize ascorbic acid. Ascorbic acid functions as a cofactor for enzymes involved in photosynthesis, synthesis of plant hormones, as an antioxidant