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
[{'content': 'Optically inactive amino acid is/are: \nSelect and explain. \nA. Threonine, B. Thyronine, C. Valine, D. Glycine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans: d. Glycine Amino acids having an asymmetric carbon atom exhibit optical activity. Asymmetry arises when 4 different groups are attached to the same carbon atomGlycine is the simplest amino acids & has no asymmetric carbon atom & therefore shows no optical activity. All others are optically activeThe mirror image forms produced with reference to the alpha carbon atom, are called D & L isomersIsoleucine er threonine have 2 optically active centres & therefore each has 4 diastereo isomers', 'role': 'assistant'}]