This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Carbohydrates, Subject name: Biochemistry
Which one of the following metabolites is used by all cells for glycolysis, glycogen synthesis, and the hexose monophosphate shunt pathway? 
Select and explain. 
A. Glucose-1-phosphate, B. Glucose-6-phosphate, C. UDP-glucose, D. Fructose-6-phosphate
B: Glucose-6-phosphate
Answer: B: Glucose-6-phosphate 
Explanation: Glucose-6-phosphate is common to all pathways. It can be converted to glucose-1-phosphate for glycogen synthesis or go directly into the pentose phosphate pathway or proceed through fructose-6-phosphate in glycolysis. UDP-glucose is formed from glucose-1-phosphate and can be used to form glycogen, lactose, glycoproteins, and glycolipids.