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
Oxaloacetate + Acetyl CoA → Citrate + CoASH. This reaction is 
Select and explain. 
A. Reversible, B. Irreversible, C. Can be reversed by catalase, D. Competitive
B: Irreversible
Answer: B: Irreversible 
Explanation: There are two irreversible steps : (i) Oxaloacetate to citrate, catalyzed by citrate synthase, and (ii) α - ketoglutarate to succinyl CoA, catalyzed by α - ketoglutarate dehydrogenase.