<prompt> Vitamin C is required for ?Posttranslational modificationSynthesis of epinephrineTyrosine metabolismAll of the above  <response>: Vitamin C ascorbic acid Ascorbic acid Vitamin C is also called antiscorbutic factor. It is very heat labile, especially in basic medium. Ascorbic acid itself is an active form. Maximum amount of vitamin C is found in adrenal coex. Ascorbic acid functions as a reducing agent and scavanger of free radicals antioxidant. Its major functions are :- i In collagen synthesis :- Vitamin C is required for post-translational modification by hydroxylation of proline and lysine residues conveing them into hydroxyproline and hydroxylysine. Thus vitamin C is essential for the conversion of procollagen to collagen, which is rich in hydroxyproline and hydroxylysine. Through collagen synthesis, it plays a role in formation of matrix of bone, cailage, dentine and connective tissue. ii Synthesis of norepinephrine from dopamine by dopamine-3-monoxygenase dopamine-13-hydroxylase requires Vitamin C. iii Carnitine synthesis iv Bile acid synthesis :- 7-a-hydroxylase requires vitamin C. v Absorption of iron is stimulated by ascorbic acid by conversion of ferric to ferrous ions. vi During adrenal steroid synthesis, ascorbic acid is required during hydroxylation reactions. vii Tyrosine metabolism - Oxidation of P-hydroxy-phenylpyruvate to homogentisate. viii Folate metabolism - Folic acid is conveed to its active form tetrahydrofolate by help of Vitamin C. 