This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
Which of the following amino acid has a high risk for CHD (Coronary heart diseases): 
Select and explain. 
A. Homocysteine, B. Methionine, C. Glycine, D. None of the above
A: Homocysteine
Answer: A: Homocysteine 
Explanation: Ans. A. HomocysteineHomocysteine is an amino acid formed during the biosynthetic pathway of cysteine from methionine. People with high serum levels of homocysteine have an unusually risk for CHD and arteriosclerosis. The molecular basis is not known, but it damage the cells lining blood vessels and increases growth of vascular smooth muscle. It can be measured by Gas chromatography, HPLC and immunoassay.