This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sources of blood glucose, Subject name: Biochemistry
Storage form of free energy in the cell is: 
Select and explain. 
A. NADH, B. ATP, C. G-6-Phosphate, D. Creatine phosphate
B: ATP
Answer: B: ATP 
Explanation: ATP is the storage form of free energy in most of the cells of the body. Creatine phosphate or Phospho-creatine is the immediate source of ATP in muscles for first 8-10 seconds. High energy compounds in biological systems are : ATP GTP UTP Creatine Phosphate Phosphoenol Pyruvate Coenzyme A 1,3-bisphospho glycerate Carbamoyl Phosphate