Glycogen metabolism – pathways MCQs With Answer

Glycogen metabolism is a central topic for B. Pharm students, covering the coordinated pathways of glycogenesis and glycogenolysis that maintain glucose homeostasis. This introduction reviews key enzymes—glycogen synthase, glycogen phosphorylase, branching and debranching enzymes—regulatory signals like insulin, glucagon and epinephrine, and cellular intermediates such as UDP‑glucose and glucose‑1‑phosphate. Understanding enzyme defects and glycogen storage diseases (Von Gierke, Pompe, Cori, McArdle) is essential for pharmacotherapy and clinical correlation. These MCQs emphasize pathway steps, regulation, clinical implications and lab detection methods to strengthen mechanistic knowledge and exam readiness. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the primary storage form of glucose in animal tissues?

• Starch
• Glycogen
• Cellulose
• Sucrose

Correct Answer: Glycogen

Q2. Which organs are the main sites for glycogen storage in humans?

• Brain and kidney
• Liver and muscle
• Adipose tissue and pancreas
• Small intestine and spleen

Correct Answer: Liver and muscle

Q3. Which enzyme catalyzes the rate-limiting step of glycogen synthesis?

• Glycogen phosphorylase
• Glycogen synthase
• Branching enzyme (4,6 transferase)
• Debranching enzyme

Correct Answer: Glycogen synthase

Q4. What protein primes the initiation of a new glycogen particle by autocatalytic addition of glucose residues?

• Glycogen synthase
• Glycogenin
• Glycogen phosphorylase
• UDP‑glucose pyrophosphorylase

Correct Answer: Glycogenin

Q5. Which enzyme is responsible for forming alpha-1,6 branch points during glycogen synthesis?

• Debranching enzyme
• Glycogen phosphorylase
• Branching enzyme (4,6 transferase)
• Phosphoglucomutase

Correct Answer: Branching enzyme (4,6 transferase)

Q6. Which enzyme removes alpha-1,6-linked branch points during glycogen degradation?

• Glycogen synthase
• Debranching enzyme
• Branching enzyme
• UDP‑glucose pyrophosphorylase

Correct Answer: Debranching enzyme

Q7. Glycogen phosphorylase catalyzes phosphorolysis of alpha-1,4 bonds to yield which product?

• Glucose
• Glucose‑1‑phosphate
• Glucose‑6‑phosphate
• UDP‑glucose

Correct Answer: Glucose‑1‑phosphate

Q8. Conversion of glycogen phosphorylase b to the active a form is achieved by phosphorylation by which enzyme?

• Phosphorylase kinase
• Protein phosphatase 1
• Glycogen synthase kinase‑3
• Phosphoglucomutase

Correct Answer: Phosphorylase kinase

Q9. Which hormone predominantly stimulates hepatic glycogenolysis during fasting?

• Insulin
• Glucagon
• Thyroxine
• Growth hormone

Correct Answer: Glucagon

Q10. In the cAMP signaling cascade, which kinase mediates phosphorylation of downstream targets to promote glycogen breakdown?

• Protein kinase A (PKA)
• AMP‑activated protein kinase (AMPK)
• Protein kinase C (PKC)
• Glycogen synthase kinase‑3 (GSK‑3)

Correct Answer: Protein kinase A (PKA)

Q11. Which phosphatase activates glycogen synthase by dephosphorylation?

• Protein phosphatase 1 (PP1)
• Protein phosphatase 2A (PP2A)
• Calcineurin
• Phosphatase and tensin homolog (PTEN)

Correct Answer: Protein phosphatase 1 (PP1)

Q12. What is the immediate activated glucose donor used by glycogen synthase?

• Glucose‑6‑phosphate
• UTP
• UDP‑glucose
• ATP

Correct Answer: UDP‑glucose

Q13. Which enzyme converts glucose‑1‑phosphate to glucose‑6‑phosphate?

• Phosphoglucomutase
• Hexokinase
• Glucose‑6‑phosphatase
• UDP‑glucose pyrophosphorylase

Correct Answer: Phosphoglucomutase

Q14. In the liver, which enzyme converts glucose‑6‑phosphate to free glucose for release into blood?

• Hexokinase
• Glucose‑6‑phosphatase
• Phosphoglucose isomerase
• Glycogen phosphorylase

Correct Answer: Glucose‑6‑phosphatase

Q15. Deficiency of the debranching enzyme causes which glycogen storage disease?

• Von Gierke disease (Type I)
• Cori disease (Type III)
• Pompe disease (Type II)
• McArdle disease (Type V)

Correct Answer: Cori disease (Type III)

Q16. Von Gierke disease (Type I) is caused by a deficiency of which enzyme?

• Glucose‑6‑phosphatase
• Acid alpha‑glucosidase
• Glycogen phosphorylase
• Debranching enzyme

Correct Answer: Glucose‑6‑phosphatase

Q17. Pompe disease (Type II) affects which cellular location and enzyme?

• Cytosolic glycogen phosphorylase deficiency
• Lysosomal acid alpha‑glucosidase deficiency
• Endoplasmic reticulum glucose‑6‑phosphatase deficiency
• Mitochondrial debranching enzyme deficiency

Correct Answer: Lysosomal acid alpha‑glucosidase deficiency

Q18. McArdle disease (Type V) is characterized by deficiency of which enzyme in muscle?

• Debranching enzyme
• Muscle glycogen phosphorylase
• Glucose‑6‑phosphatase
• Glycogen synthase

Correct Answer: Muscle glycogen phosphorylase

Q19. Which metabolite allosterically activates glycogen synthase?

• AMP
• Glucose‑6‑phosphate
• ATP
• Fructose‑2,6‑bisphosphate

Correct Answer: Glucose‑6‑phosphate

Q20. High levels of which molecule inhibit hepatic glycogen phosphorylase activity?

• Glucose
• Cortisol
• AMP
• Epinephrine

Correct Answer: Glucose

Q21. The interconversion between glucose‑1‑phosphate and glucose‑6‑phosphate is reversible and catalyzed by which enzyme?

• Hexokinase
• Phosphoglucomutase
• Glucose‑6‑phosphatase
• Glycogen phosphorylase

Correct Answer: Phosphoglucomutase

Q22. UDP‑glucose pyrophosphorylase uses which nucleotide triphosphate to activate glucose?

• ATP
• CTP
• UTP
• GTP

Correct Answer: UTP

Q23. The first glucose residues in a new glycogen particle are covalently linked to which amino acid residue of glycogenin?

• Serine
• Tyrosine
• Lysine
• Histidine

Correct Answer: Tyrosine

Q24. Increased branching of glycogen primarily serves what functional purpose?

• Decrease solubility of glycogen
• Reduce number of non‑reducing ends
• Increase number of non‑reducing ends to speed synthesis and degradation
• Prevent phosphorylation by kinases

Correct Answer: Increase number of non‑reducing ends to speed synthesis and degradation

Q25. Which tissue’s glycogen phosphorylase is chiefly regulated by AMP as an allosteric activator during exercise?

• Liver
• Muscle
• Adipose tissue
• Brain

Correct Answer: Muscle

Q26. Insulin promotes glycogen synthesis primarily by which mechanisms?

• Activating PKA to phosphorylate glycogen synthase
• Stimulating PP1 activity and inhibiting GSK‑3 via Akt pathway
• Increasing glucagon secretion
• Directly cleaving glycogen phosphorylase

Correct Answer: Stimulating PP1 activity and inhibiting GSK‑3 via Akt pathway

Q27. Phosphorylase kinase is activated by which of the following?

• Dephosphorylation by PP1
• Phosphorylation by PKA and binding of Ca2+/calmodulin
• Binding of insulin to its receptor
• High levels of glucose‑6‑phosphate only

Correct Answer: Phosphorylation by PKA and binding of Ca2+/calmodulin

Q28. At what point does glycogen phosphorylase stop cleaving glucose residues when it approaches a branch point?

• Immediately adjacent to the branch point
• When four residues remain before the branch point
• After removing all residues to the branch point
• It does not stop; it removes branch points

Correct Answer: When four residues remain before the branch point

Q29. Debranching enzyme exhibits which two catalytic activities?

• Transferase (4:4) and phosphorylase activities
• Transferase (4:4) and alpha‑1,6‑glucosidase activities
• Branching (4:6 transferase) and synthase activities
• Kinase and phosphatase activities

Correct Answer: Transferase (4:4) and alpha‑1,6‑glucosidase activities

Q30. Which histochemical stain is commonly used to demonstrate glycogen in tissue sections?

• Hematoxylin and eosin (H&E)
• Periodic acid‑Schiff (PAS)
• Silver stain
• Oil Red O

Correct Answer: Periodic acid‑Schiff (PAS)

Q31. Which of the following clinical features is most characteristic of McArdle disease?

• Severe fasting hypoglycemia in infants
• Cardiomegaly and respiratory failure in infancy
• Exercise intolerance with myoglobinuria
• Hepatomegaly with lactic acidosis

Correct Answer: Exercise intolerance with myoglobinuria

Q32. Enzyme replacement therapy with alglucosidase alfa is used to treat which glycogen storage disease?

• Von Gierke disease (Type I)
• Pompe disease (Type II)
• Cori disease (Type III)
• McArdle disease (Type V)

Correct Answer: Pompe disease (Type II)

Q33. Which nucleotide sugar is directly synthesized from glucose‑1‑phosphate and UTP?

• ADP‑glucose
• UDP‑glucose
• GDP‑glucose
• CDP‑glucose

Correct Answer: UDP‑glucose

Q34. In muscle during intense exercise, which allosteric effector directly activates glycogen phosphorylase?

• Glucose
• ATP
• AMP
• Insulin

Correct Answer: AMP

Q35. Which enzyme regulates entry of glucose into the glycolytic pathway and is distinct from the glycogen pathway enzymes?

• Hexokinase/glucokinase
• Glycogen synthase
• Glycogen phosphorylase
• Debranching enzyme

Correct Answer: Hexokinase/glucokinase

Q36. The reducing end of a glycogen molecule is normally:

• Free and reactive
• Covalently linked to glycogenin
• Multiple reducing ends per molecule
• Linked to glucose‑6‑phosphate

Correct Answer: Covalently linked to glycogenin

Q37. What is the major fate of glucose derived from muscle glycogen breakdown?

• Released into blood to maintain blood glucose
• Converted to glycogen in the liver
• Used in glycolysis within muscle for ATP production
• Converted to free fatty acids

Correct Answer: Used in glycolysis within muscle for ATP production

Q38. Which enzyme is directly inhibited by glycogen synthase kinase‑3 (GSK‑3)?

• Glycogen phosphorylase
• Glycogen synthase
• Phosphoglucomutase
• Debranching enzyme

Correct Answer: Glycogen synthase

Q39. Which molecule acts as a key allosteric signal reflecting cellular energy status and influences glycogen metabolism?

• cAMP only
• AMP/ATP ratio
• Cholesterol levels
• Free fatty acids

Correct Answer: AMP/ATP ratio

Q40. In bacterial glycogen synthesis, the activated glucose donor is often ADP‑glucose; in mammals it is:

• UDP‑glucose
• CDP‑glucose
• ADP‑glucose
• GTP‑glucose

Correct Answer: UDP‑glucose

Q41. Which enzyme removes the outer three glucose residues from a branch and transfers them to another chain during debranching?

• Branching enzyme
• Transferase activity of debranching enzyme
• Glycogen phosphorylase
• Glucose‑6‑phosphatase

Correct Answer: Transferase activity of debranching enzyme

Q42. Which statement accurately describes the role of phosphoglucomutase in glycogen metabolism?

• It synthesizes UDP‑glucose directly from glucose
• It interconverts glucose‑1‑phosphate and glucose‑6‑phosphate
• It cleaves alpha‑1,6 linkages in glycogen
• It phosphorylates glycogen synthase

Correct Answer: It interconverts glucose‑1‑phosphate and glucose‑6‑phosphate

Q43. Which of the following is a clinical consequence of deficient hepatic glucose‑6‑phosphatase activity?

• Post‑prandial hyperglycemia only
• Severe fasting hypoglycemia and lactic acidosis
• Muscle cramps during exercise
• Excessive glycogen branching

Correct Answer: Severe fasting hypoglycemia and lactic acidosis

Q44. Which regulatory event links calcium signaling to increased glycogenolysis in muscle during contraction?

• Calcium activates glycogen synthase directly
• Calcium binds calmodulin to activate phosphorylase kinase
• Calcium inhibits phosphorylase kinase
• Calcium stimulates insulin secretion

Correct Answer: Calcium binds calmodulin to activate phosphorylase kinase

Q45. Which of the following best explains why glycogen is highly branched from a pharmacological delivery perspective?

• Branching reduces water solubility, slowing drug diffusion
• Branching increases points for rapid cleavage, affecting rate of glucose release
• Branching creates covalent drug binding sites
• Branching prevents enzymatic access entirely

Correct Answer: Branching increases points for rapid cleavage, affecting rate of glucose release

Q46. During prolonged fasting, approximately how long can hepatic glycogen stores maintain blood glucose in humans?

• 30 minutes
• 4–6 hours
• About 24 hours
• Several weeks

Correct Answer: About 24 hours

Q47. Which condition is characterized by accumulation of glycogen with abnormal structure due to branching enzyme deficiency?

• Andersen disease (Type IV)
• Von Gierke disease (Type I)
• McArdle disease (Type V)
• Cori disease (Type III)

Correct Answer: Andersen disease (Type IV)

Q48. Which molecule directly allosterically inhibits glycogen synthase when energy is low?

• Glucose‑6‑phosphate
• AMP‑activated protein kinase (AMPK) phosphorylation indirectly via AMP
• Insulin
• High NADH

Correct Answer: AMP‑activated protein kinase (AMPK) phosphorylation indirectly via AMP

Q49. Which laboratory finding helps confirm abnormal glycogen storage in a liver biopsy?

• Negative PAS staining
• Strong PAS positivity that is diastase sensitive
• Reduced lipid droplets only
• Iron accumulation on Prussian blue stain

Correct Answer: Strong PAS positivity that is diastase sensitive

Q50. In pharmacology and biochemistry teaching, which activated sugar is emphasized as the glucose donor for mammalian glycogen synthesis?

• ADP‑glucose
• UDP‑glucose
• GDP‑glucose
• ATP‑glucose

Correct Answer: UDP‑glucose

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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