This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Glycolysis, Subject name: Biochemistry
Pyruvate can be conveed directly into all of the following EXCEPT: 
Select and explain. 
A. Phosphoenol Pyruvate, B. Alanine, C. Acetyl CoA, D. Lactate
A: Phosphoenol Pyruvate
Answer: A: Phosphoenol Pyruvate 
Explanation: Pyruvate can be conveed directly into all of the following except phosphoenol pyruvate. Phosphoenol pyruvate to pyruvate conversion Catalyzed by pyruvate kinase. Irreversible step So pyruvate can't be conveed directly into phosphoenol pyruvate. (Option b) During fasting, transamination reaction in muscles produces alanine from pyruvate by enzyme ALT , known as Cahill cycle (Glucose-Alanine Cycle). (Option c) In mitochondria,pyruvate forms Acetyl CoA by enzyme pyruvate dehydrogenase (link reaction). (Option d) In exercising muscles, pyruvate gets conveed to lactate due to anaerobic conditions by using enzyme LDH (reversible enzyme) (Cori's cycle)