Bchintermediate
Explain how liver and muscle glycogen differ in physiological role and glucose release.
Answer
Liver glycogen helps maintain blood glucose because liver cells contain glucose-6-phosphatase, which converts glucose-6-phosphate to free glucose. Muscle glycogen supplies glucose units for glycolysis within muscle; muscle lacks glucose-6-phosphatase and therefore does not release free glucose from this pathway.
Explanation
### What a good answer covers
- Liver glycogen is a reserve that can help replenish blood glucose.
- Liver glucose-6-phosphatase converts glucose-6-phosphate to free glucose.
- Muscle glycogen primarily supports glycolysis in the muscle itself.
- Muscle lacks glucose-6-phosphatase, so it cannot complete the same free-glucose release step.
### Terms
- **Glycogen**: A branched glucose-storage polymer.
- **Glucose-6-phosphatase**: The enzyme that removes phosphate from glucose-6-phosphate.
### Remember
The presence or absence of glucose-6-phosphatase explains the different tissue roles.
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