Question 79

Question:

Vitamin C deficiency results in scurvy. Vitamin C functions as a co-factor in which of the following steps of the collagen synthesis cascade?

Correct Answer: D.  Hydroxylation of preprocollagen

The hydroxylation of specific proline and lysine residues on the preprocollagen strand requires vitamin C as a cofactor in the endoplasmic reticulum. There, the pro-alpha chain of collagen is glycosylated to form the triple-helixed procollagen. Procollagen is then sent to the Golgi apparatus and is exocytosed from the cell, where the ends are cleaved to form tropocollagen. These molecules are cross-linked to form collagen fibrils. Unlike most proteins, post-translational modification occurs in the RER rather than the Golgi apparatus.