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': "What is the substrate for the only physiologically irreversible reaction in the Kreb's Citric acid cycle? \nSelect and explain. \nA. Citrate, B. Alpha ketoglutarate, C. Succinate, D. Malate", 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Alphaketoglutarate', 'role': 'assistant'}]