Vitamin C contributing to the more severe symptoms of scurvy. More generally, the biochemical role of vitamin C is to act as an antioxidant (a reducing agent) by donating electrons to various enzymatic and non-enzymatic reactions. Doing so converts vitamin C to an oxidized state - either as semidehydroascorbic acid or dehydroascorbic acid. These compounds can be restored to a reduced state by glutathione and NADPH-dependent enzymatic mechanisms. In plants, vitamin C is a substrate for ascorbate peroxidase. This enzyme utilizes ascorbate to neutralize toxic hydrogen peroxide (HO) by converting it to water (HO). Scurvy is a disease resulting from a deficiency
Vitamin B12 deficiency anemia antibodies for parietal cells; however, only 50% of all individuals in the general population with these antibodies have pernicious anemia. Forms of vitamin B deficiency other than PA must be considered in the differential diagnosis of megaloblastic anemia. For example, a B-deficient state which causes megaloblastic anemia and which may be mistaken for classical PA may be caused by infection with the tapeworm "Diphyllobothrium latum", possibly due to the parasite's competition with host for vitamin B. The classic test for PA, the Schilling test, is no longer widely used, as more efficient methods are available. This historic test consisted, in