Glycolysis – pathway MCQs With Answer is a concise, student-friendly resource tailored for B. Pharm learners to master the central steps of glucose metabolism. This introduction covers key glycolytic enzymes, regulation points (hexokinase, PFK-1, pyruvate kinase), ATP and NADH yields, anaerobic vs aerobic fates, and clinically relevant inhibitors and disorders. Emphasis on mechanism, energetics, tissue-specific differences, and links to the TCA cycle and pentose phosphate pathway helps build strong biochemical foundations for pharmacology and therapeutics. Ideal for exam prep and quick revision with targeted multiple-choice practice. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the primary cellular location of the glycolytic pathway?
- Cytosol
- Mitochondrial matrix
Correct Answer: Cytosol
Q2. Glycolysis converts one molecule of glucose into which end product under anaerobic conditions in human cells?
Correct Answer: Lactate
Q3. Which enzyme catalyzes the phosphorylation of glucose to glucose-6-phosphate in most tissues?
- Glucokinase
- Hexokinase
- Phosphofructokinase-1
- Glucose-6-phosphatase
Correct Answer: Hexokinase
Q4. Which step is the committed, rate-limiting step of glycolysis?
Correct Answer: Phophofructokinase-1 reaction (F6P → F1,6BP)
Q5. How many net ATP molecules are produced per glucose molecule by glycolysis alone (embden-meyerhof pathway) under aerobic conditions in most cells?
- 4 ATP net
- 2 ATP net
- 36 ATP net
- 30 ATP net
Correct Answer: 2 ATP net
Q6. Which glycolytic enzyme produces NADH during the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate?
- Triose phosphate isomerase
- Glyceraldehyde-3-phosphate dehydrogenase
- Phosphoglycerate kinase
- Enolase
Correct Answer: Glyceraldehyde-3-phosphate dehydrogenase
Q7. Which enzyme catalyzes substrate-level phosphorylation generating ATP in glycolysis?
- Hexokinase
- Phosphoglucose isomerase
- Phosphoglycerate kinase
- Pyruvate carboxylase
Correct Answer: Phosphoglycerate kinase
Q8. Glucokinase differs from hexokinase in that glucokinase:
- Has a lower Km for glucose and acts at low glucose concentrations
- Is inhibited by glucose-6-phosphate
- Has a higher Km and is present in liver and pancreatic beta cells
- Is active in red blood cells
Correct Answer: Has a higher Km and is present in liver and pancreatic beta cells
Q9. Fructose-2,6-bisphosphate regulates glycolysis by:
- Inhibiting phosphofructokinase-1
- Activating phosphofructokinase-1
- Activating fructose-1,6-bisphosphatase
- Inhibiting hexokinase
Correct Answer: Activating phosphofructokinase-1
Q10. Which cofactor is required by glyceraldehyde-3-phosphate dehydrogenase?
- NAD+
- NADP+
- FAD
- Biotin
Correct Answer: NAD+
Q11. The conversion of phosphoenolpyruvate to pyruvate is catalyzed by which enzyme?
- Pyruvate kinase
- Pyruvate dehydrogenase
- Enolase
- Phosphoenolcarboxykinase
Correct Answer: Pyruvate kinase
Q12. Arsenate (AsO4^3−) inhibits glycolysis by:
- Directly inhibiting hexokinase
- Substituting for inorganic phosphate in glyceraldehyde-3-phosphate dehydrogenase reaction, uncoupling ATP formation
- Blocking pyruvate kinase
- Inhibiting lactate dehydrogenase
Correct Answer: Substituting for inorganic phosphate in glyceraldehyde-3-phosphate dehydrogenase reaction, uncoupling ATP formation
Q13. In red blood cells, which enzyme converts pyruvate to lactate to regenerate NAD+?
- PDT (pyruvate dehydrogenase complex)
- Lactate dehydrogenase
- Pyruvate carboxylase
- Alanine transaminase
Correct Answer: Lactate dehydrogenase
Q14. Which intermediate is split by aldolase to form glyceraldehyde-3-phosphate and dihydroxyacetone phosphate?
Correct Answer: Fructose-1,6-bisphosphate
Q15. Triose phosphate isomerase catalyzes the reversible conversion between:
Correct Answer: Dihydroxyacetone phosphate and glyceraldehyde-3-phosphate
Q16. Which enzyme produces 2-phosphoglycerate from 3-phosphoglycerate?
- Phosphoglycerate mutase
- Enolase
- Phosphoglucose isomerase
- Phosphoglycerate kinase
Correct Answer: Phosphoglycerate mutase
Q17. The Warburg effect in cancer cells describes increased glycolysis even in the presence of oxygen. Which term best characterizes this phenomenon?
- Oxidative phosphorylation upregulation
- Aerobic glycolysis
- Gluconeogenesis activation
- Ketogenesis
Correct Answer: Aerobic glycolysis
Q18. Which molecule allosterically inhibits phosphofructokinase-1 (PFK-1)?
- AMP
- Fructose-2,6-bisphosphate
- ATP
- ADP
Correct Answer: ATP
Q19. Which shuttle transfers cytosolic NADH electrons into mitochondria yielding approximately 1.5 ATP per NADH?
- Malate-aspartate shuttle
- Glycerol-3-phosphate shuttle
- Pentose phosphate shuttle
Correct Answer: Glycerol-3-phosphate shuttle
Q20. Which glycolytic intermediate is directly involved in the synthesis of 2,3-bisphosphoglycerate in erythrocytes?
- 1,3-bisphosphoglycerate
Correct Answer: 1,3-bisphosphoglycerate
Q21. Which enzyme deficiency is commonly associated with chronic hemolytic anemia due to impaired ATP production in erythrocytes?
Correct Answer: Pyruvate kinase deficiency
Q22. Which regulatory hormone stimulates glycolysis in liver by increasing fructose-2,6-bisphosphate levels?
- Glucagon
- Insulin
- Adrenaline
- Cortisol
Correct Answer: Insulin
Q23. The enzyme enolase catalyzes which conversion in glycolysis?
Correct Answer: 2-phosphoglycerate → phosphoenolpyruvate
Q24. Which glycolytic intermediate can be diverted into the pentose phosphate pathway for NADPH production?
Correct Answer: Glucose-6-phosphate
Q25. Which of the following inhibitors specifically blocks enolase activity?
Correct Answer: Fluoride ion (F−)
Q26. What is the fate of pyruvate in aerobic tissues with functional mitochondria?
- Converted to lactate by LDH
- Converted to acetyl-CoA by pyruvate dehydrogenase
- Converted to oxaloacetate by pyruvate carboxylase in cytosol
- Directly oxidized to CO2 in cytosol
Correct Answer: Converted to acetyl-CoA by pyruvate dehydrogenase
Q27. Which substrate-level phosphorylation step in glycolysis directly generates ATP?
Correct Answer: 1,3-bisphosphoglycerate → 3-phosphoglycerate
Q28. Which metabolite is an allosteric activator of pyruvate kinase in the liver?
- Citrate
- Alanine
- Fructose-1,6-bisphosphate
Correct Answer: Fructose-1,6-bisphosphate
Q29. Iodoacetate inhibits glycolysis by modifying which enzyme’s active site sulfhydryl group?
- Glyceraldehyde-3-phosphate dehydrogenase
- Hexokinase
Correct Answer: Glyceraldehyde-3-phosphate dehydrogenase
Q30. During intense exercise, skeletal muscle shifts to anaerobic glycolysis primarily because:
- Oxygen supply exceeds demand
- Mitochondria become inactive
- ATP demand outpaces oxygen delivery causing NAD+ regeneration via lactate formation
- Glycogen stores are depleted immediately
Correct Answer: ATP demand outpaces oxygen delivery causing NAD+ regeneration via lactate formation
Q31. Which enzyme interconverts fructose-6-phosphate and glucose-6-phosphate?
- Phosphofructokinase-1
- Phosphoglucose isomerase
- Hexokinase
- Glucose-6-phosphatase
Correct Answer: Phosphoglucose isomerase
Q32. 2,3-Bisphosphoglycerate (2,3-BPG) in erythrocytes influences oxygen binding by:
- Increasing hemoglobin’s affinity for oxygen
- Decreasing hemoglobin’s affinity for oxygen
- Directly generating more ATP
- Converting oxygen to superoxide
Correct Answer: Decreasing hemoglobin’s affinity for oxygen
Q33. Which enzyme catalyzes the reversible conversion of 3-phosphoglycerate to 2-phosphoglycerate?
- Phosphoglucose isomerase
- Phosphoglycerate mutase
- Enolase
- Triose phosphate isomerase
Correct Answer: Phosphoglycerate mutase
Q34. What is the immediate product when fructokinase acts on fructose in hepatic fructose metabolism before entering glycolysis?
- Dihydroxyacetone phosphate
Correct Answer: Fructose-1-phosphate
Q35. Which metabolite serves as an allosteric inhibitor of hexokinase in many tissues?
Correct Answer: Glucose-6-phosphate
Q36. Which enzyme catalyzes the formation of 1,3-bisphosphoglycerate during glycolysis?
- Glyceraldehyde-3-phosphate dehydrogenase
- Phosphoglycerate kinase
- Enolase
Correct Answer: Glyceraldehyde-3-phosphate dehydrogenase
Q37. Which metabolic pathway provides glyceraldehyde-3-phosphate for glycolysis during fructose metabolism in muscle?
Correct Answer: Fructose is phosphorylated to fructose-6-phosphate by hexokinase
Q38. Which of the following increases PFK-1 activity in liver indirectly by affecting levels of fructose-2,6-bisphosphate?
- Glucagon via PKA-mediated phosphorylation
- Insulin via activation of phosphofructokinase-2 (PFK-2)
- Cortisol reducing fructose-2,6-bisphosphate
- High ATP levels
Correct Answer: Insulin via activation of phosphofructokinase-2 (PFK-2)
Q39. Which metabolite directly donates a phosphate to ADP to form ATP via pyruvate kinase?
Correct Answer: Phosphoenolpyruvate
Q40. A deficiency of phosphofructokinase in muscle primarily presents with:
- Hyperglycemia
- Exercise intolerance and muscle cramps
- Lactic acidosis at rest only
Correct Answer: Exercise intolerance and muscle cramps
Q41. Which enzyme catalyzes the conversion of glucose-6-phosphate to 6-phosphogluconolactone in the pentose phosphate pathway, linking carbohydrate metabolism to NADPH production?
- Glucose-6-phosphate dehydrogenase
- Phosphoglucose isomerase
- Hexokinase
- Transketolase
Correct Answer: Glucose-6-phosphate dehydrogenase
Q42. Which condition would decrease glycolytic flux in the liver?
- High insulin-to-glucagon ratio
- High fructose-2,6-bisphosphate concentration
- Elevated glucagon signaling
- High AMP concentration
Correct Answer: Elevated glucagon signaling
Q43. Which of the following is TRUE about pyruvate kinase regulation?
- It is inhibited by fructose-1,6-bisphosphate
- It is activated by alanine
- It is inhibited by phosphorylation in response to glucagon in liver
- It requires biotin as a cofactor
Correct Answer: It is inhibited by phosphorylation in response to glucagon in liver
Q44. Which intermediate of glycolysis contains a high-energy acyl phosphate bond used to generate ATP?
Correct Answer: 1,3-bisphosphoglycerate
Q45. Which enzyme catalyzes the reversible isomerization of glucose-6-phosphate to fructose-6-phosphate and is essential for continued glycolysis?
- Phosphoglucose isomerase
- Glucose-6-phosphatase
- Phosphofructokinase-1
- Hexokinase
Correct Answer: Phosphoglucose isomerase
Q46. What effect does high citrate concentration have on glycolysis?
- Activates PFK-1, increasing glycolysis
- Inhibits PFK-1, decreasing glycolysis
- Directly increases hexokinase activity
- Converts pyruvate to lactate
Correct Answer: Inhibits PFK-1, decreasing glycolysis
Q47. In the Cori cycle, lactate produced by muscle is transported to the liver and converted back to:
Correct Answer: Glucose via gluconeogenesis
Q48. Which metabolic defect would lead to accumulation of fructose-1-phosphate and cause hypoglycemia after fructose ingestion?
Correct Answer: Aldolase B deficiency (hereditary fructose intolerance)
Q49. In glycolysis, the conversion of dihydroxyacetone phosphate to glyceraldehyde-3-phosphate ensures that:
- Both triose molecules are identical for further metabolism
Correct Answer: Both triose molecules are identical for further metabolism
Q50. Which pharmacologic or toxic agent is known to inhibit pyruvate dehydrogenase, thereby affecting pyruvate entry into the TCA cycle and increasing lactate production?
Correct Answer: Arsenite (arsenate) and arsenic compounds
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