Skeletal muscle stores a large amount of glycogen, yet muscle glycogenolysis cannot directly correct hypoglycemia. Which single enzymatic deficit explains this?
- A Muscle lacks glycogen phosphorylase
- B Muscle lacks glucose-6-phosphatase ✓
- C Muscle lacks debranching enzyme
- D Muscle lacks phosphoglucomutase
Correct answer: B. Muscle lacks glucose-6-phosphatase
Explanation
Muscle breaks glycogen down to glucose-6-phosphate but lacks glucose-6-phosphatase, so the phosphate cannot be removed and free glucose cannot leave the myocyte. The carbon is used locally through glycolysis. Muscle does contain phosphorylase, debranching enzyme, and phosphoglucomutase, so the other options describe enzymes that are present and functional in skeletal muscle.
Reference: Lippincott's Illustrated Reviews: Biochemistry, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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