Glycogen is broken down into glucose-1-phosphate. What must happen before that product can enter the glycolytic pathway?
AIt must be converted to glucose-6-phosphate
BIt must be converted to fructose-6-phosphate
CIt must lose its phosphate group entirely
DIt must be carried into the mitochondrion
Answer & Solution
Correct answer: A. It must be converted to glucose-6-phosphate
1. Glycogen is hydrolysed into glucose monomers in the form of glucose-1-phosphate when blood sugar drops.
2. That glucose-1-phosphate is converted into glucose-6-phosphate in both muscle and liver cells.
3. It is this converted product that enters the glycolytic pathway.
4. Glucose-6-phosphate is the same intermediate that hexokinase makes at the very start of glycolysis.
5. Fructose-6-phosphate lies one step further on, so entry there would skip a regulated step.
6. Losing the phosphate would let the sugar leave the cell, which is the opposite of what the cell wants.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 7 "Cellular Respiration", section 7.6 Connections of Carbohydrate, Protein, and Lipid Metabolic Pathways_
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