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
Hydroxylation of proline in collagen requires which of the following: 
Select and explain. 
A. Vitamin C, B. Fe2++, C. a-ketoglutarate, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Ans. D. All of the aboveProline and Lysine are hydroxylated to form hydroxyl proline and hydroxyl lysine in the presence of enzyme hydroxylase and requires Fe2++' ascorbic acid (Vitamin C), oxygen and a- ketoglutarate.