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
First substrate of Kreb’s cycle is 
Select and explain. 
A. Pyruvate, B. Glycine, C. Alanine, D. Lipoprotein
A: Pyruvate
Answer: A: Pyruvate 
Explanation: Pyruvate, the end product of aerobic glycolysis is transported into mitochondria by specific pyruvate transporter, where it is converted to acetyl CoA by pyruvate dehydrogenase (PDH) complex.