This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: TCA Cycle, Subject name: Biochemistry
Rate limiting step of TCA : 
Select and explain. 
A. Citrate synthase, B. Isocitrate dehydrogenase, C. Alpha-ketoglutarate dehydrogenase, D. All
D: All
Answer: D: All 
Explanation: 3 enzymes which are rate limiting in TCA cycle Irreversible steps of TCA 1. Citrate Synthase 1. Citrate Synthase (preferred) 2. Isocitrate Dehydrogenase 2. Alpha-Ketoglutarate Dehydrogenase. 3. Alpha-Ketoglutarate Dehydrogenase