This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which is the most abundant amino acid in the structure of collagen 
Select and explain. 
A. Proline, B. Glycine, C. Hydroxy proline, D. Phenylalanine
B: Glycine
Answer: B: Glycine 
Explanation: Glycine is the most abundant amino acid in collagen, as every 3rd amino acid in the structure is glycine.
Note: Phenylalanine is not seen in collagen.