This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of carbohydrate, Subject name: Biochemistry
Collagen has which amino acid? 
Select and explain. 
A. Tryptophan, B. Glycine, C. Theonine, D. Tyrosine
B: Glycine
Answer: B: Glycine 
Explanation: Each polypeptide chain of collagen has about 1000 amino acid residues. amino acid composition of collagen is quite unique. About 33% of the amino acids are glycine, that is, every third residue is glycineRef: DM Vasudevan, 7th edition, page no: 720