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
[{'content': 'In TCA cycle, citrate is conveed into cis-aconitate by which mechanism? \nSelect and explain. \nA. Loss of H+, B. Loss of phosphate, C. Loss of H2O molecule, D. Loss of carbon dioxide molecule', 'role': 'user'}, {'content': 'Answer: C \nExplanation: 2nd Step: Formation of Isocitrate, Citrate is isomerized to isocitrate by aconitase (Step 2, Fig.18.2). This reaction is a two-step process. At first, one water molecule is removed from citrate forming cis aconitate; a transient compound with a very sho half-life. Immediately, one water molecule is added to aconitate to form isocitrate. Thus the position of the hydroxyl group is shifted.Ref: DM Vasudevan, 7th edition', 'role': 'assistant'}]