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 + CoASHThis reaction is: 
Select and explain. 
A. Reversible, B. Irreversible, C. Can be reversed by catalase, D. Competitive
B: Irreversible
Answer: B: Irreversible 
Explanation: B i.e. IrreversibleFormation of Citric Acid from Acetyl -COA and Oxaloacetate (OAA) is 1st and irreversible step of TCA, giving 7.8 K cal (exergonic reactionQ)