Glycolysis – energetics MCQs With Answer

Glycolysis – Energetics MCQs With Answer

Glycolysis is a central metabolic pathway that converts glucose into pyruvate while yielding energy-rich molecules essential for cellular function. For B. Pharm students, mastering glycolytic energetics—ATP investment and payoff, NADH generation, substrate-level phosphorylation, and regulatory checkpoints—is crucial for understanding drug action, metabolic diseases, and biochemical pharmacology. This set emphasizes enzyme mechanisms (hexokinase, phosphofructokinase-1, pyruvate kinase, GAPDH), thermodynamics (ΔG and high-energy intermediates like PEP and 1,3-BPG), and clinical correlations (anaerobic lactate formation, enzyme deficiencies). Clear, targeted MCQs will strengthen conceptual and application-level knowledge for exams and professional practice. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the net ATP yield from one molecule of glucose through glycolysis under aerobic conditions?

• 4 ATP per glucose
• 2 ATP per glucose
• 3 ATP per glucose
• 0 ATP per glucose

Correct Answer: 2 ATP per glucose

Q2. How many NADH molecules are produced per glucose during glycolysis?

• 1 NADH
• 4 NADH
• 2 NADH
• 0 NADH

Correct Answer: 2 NADH

Q3. Under anaerobic conditions in human muscle, the primary end-product of glycolysis is:

• Acetyl-CoA
• Ethanol
• Lactate
• Oxaloacetate

Correct Answer: Lactate

Q4. Which two enzymes consume ATP in the preparatory phase of glycolysis?

• Glyceraldehyde-3-phosphate dehydrogenase and enolase
• Hexokinase and phosphofructokinase-1
• Pyruvate kinase and phosphoglycerate kinase
• Aldolase and triose phosphate isomerase

Correct Answer: Hexokinase and phosphofructokinase-1

Q5. Which glycolytic steps are considered essentially irreversible under cellular conditions?

• Glucose-6-phosphate isomerase, aldolase, enolase
• Hexokinase, phosphofructokinase-1, pyruvate kinase
• Triose phosphate isomerase, phosphoglycerate mutase, lactate dehydrogenase
• Glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase, enolase

Correct Answer: Hexokinase, phosphofructokinase-1, pyruvate kinase

Q6. Substrate-level phosphorylation in glycolysis occurs at which reactions?

• Hexokinase and phosphofructokinase-1
• Glyceraldehyde-3-phosphate dehydrogenase and enolase
• Phosphoglycerate kinase (1,3-BPG → 3-PG) and pyruvate kinase (PEP → pyruvate)
• Aldolase and triose phosphate isomerase

Correct Answer: Phosphoglycerate kinase (1,3-BPG → 3-PG) and pyruvate kinase (PEP → pyruvate)

Q7. Which enzyme catalyzes the oxidation of glyceraldehyde-3-phosphate producing NADH?

• Phosphoglycerate kinase
• Glyceraldehyde-3-phosphate dehydrogenase
• Pyruvate kinase
• Hexokinase

Correct Answer: Glyceraldehyde-3-phosphate dehydrogenase

Q8. The most potent allosteric activator of phosphofructokinase-1 in liver and muscle is:

• ATP
• Citrate
• Fructose-2,6-bisphosphate
• Alanine

Correct Answer: Fructose-2,6-bisphosphate

Q9. Which molecules are key allosteric inhibitors of phosphofructokinase-1?

• AMP and fructose-2,6-bisphosphate
• ATP and citrate
• ADP and F1,6BP
• Glucose and insulin

Correct Answer: ATP and citrate

Q10. Which hexokinase isozyme is NOT inhibited by its product glucose-6-phosphate and predominates in the liver?

• Hexokinase I
• Glucokinase (hexokinase IV)
• Hexokinase II
• Hexokinase III

Correct Answer: Glucokinase (hexokinase IV)

Q11. Pyruvate kinase is allosterically activated by which glycolytic intermediate (feed-forward activation)?

• Glucose-6-phosphate
• Fructose-1,6-bisphosphate
• ATP
• Citrate

Correct Answer: Fructose-1,6-bisphosphate

Q12. Pyruvate kinase is inhibited by which of the following?

• ADP and fructose-1,6-bisphosphate
• ATP and alanine
• AMP and phosphate
• Insulin and F2,6BP

Correct Answer: ATP and alanine

Q13. Which enzyme catalyzes the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate?

• Phosphoglycerate kinase
• Glyceraldehyde-3-phosphate dehydrogenase
• Enolase
• Phosphoglycerate mutase

Correct Answer: Glyceraldehyde-3-phosphate dehydrogenase

Q14. Approximately how many ATP molecules are synthesized from one mitochondrial NADH via oxidative phosphorylation (modern estimate)?

• 3 ATP
• 2.5 ATP
• 1 ATP
• 4 ATP

Correct Answer: 2.5 ATP

Q15. Which shuttle transfers cytosolic NADH into mitochondria with minimal loss of reducing equivalents (~2.5 ATP per NADH)?

• Glycerol-3-phosphate shuttle
• Malate-aspartate shuttle
• Urea shuttle
• Hexose monophosphate shuttle

Correct Answer: Malate-aspartate shuttle

Q16. The glycerol-3-phosphate shuttle transfers cytosolic reducing equivalents to mitochondria but yields less ATP per NADH; its approximate yield is:

• 2.5 ATP per NADH
• 1.5 ATP per NADH
• 3.5 ATP per NADH
• 0.5 ATP per NADH

Correct Answer: 1.5 ATP per NADH

Q17. Which glycolytic intermediate is a high-energy phosphoryl donor and is formed directly before ATP generation by phosphoglycerate kinase?

• Fructose-1,6-bisphosphate
• 1,3-Bisphosphoglycerate (1,3-BPG)
• 3-Phosphoglycerate
• Glucose-6-phosphate

Correct Answer: 1,3-Bisphosphoglycerate (1,3-BPG)

Q18. Which enzyme catalyzes the final ATP-generating step converting phosphoenolpyruvate (PEP) to pyruvate?

• Enolase
• Pyruvate kinase
• Phosphoglycerate kinase
• Pyruvate dehydrogenase

Correct Answer: Pyruvate kinase

Q19. What is the primary role of NAD+ in glycolysis?

• Allosteric activator of hexokinase
• Electron acceptor oxidizing glyceraldehyde-3-phosphate to generate NADH
• Substrate for ATP synthesis
• Carrier of inorganic phosphate

Correct Answer: Electron acceptor oxidizing glyceraldehyde-3-phosphate to generate NADH

Q20. The committed step of glycolysis is catalyzed by which enzyme?

• Hexokinase
• Phosphofructokinase-1 (PFK-1)
• Pyruvate kinase
• Glucokinase

Correct Answer: Phosphofructokinase-1 (PFK-1)

Q21. Which enzyme interconverts dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate?

• Triose phosphate isomerase
• Aldolase
• Phosphoglycerate mutase
• Enolase

Correct Answer: Triose phosphate isomerase

Q22. Aldolase acts on fructose-1,6-bisphosphate to yield which two triose phosphates?

• Glyceraldehyde-3-phosphate and dihydroxyacetone phosphate
• 3-Phosphoglycerate and 2-phosphoglycerate
• Phosphoenolpyruvate and pyruvate
• Glucose and fructose

Correct Answer: Glyceraldehyde-3-phosphate and dihydroxyacetone phosphate

Q23. Which glycolytic enzyme is inhibited by fluoride, a classical enzyme inhibitor used in blood sample preservation?

• Hexokinase
• Enolase
• Pyruvate kinase
• Glyceraldehyde-3-phosphate dehydrogenase

Correct Answer: Enolase

Q24. Arsenate toxicity affects glycolysis by:

• Blocking hexokinase irreversibly
• Replacing inorganic phosphate and preventing ATP formation at phosphoglycerate kinase
• Inhibiting lactate dehydrogenase
• Stimulating phosphofructokinase-1 activity

Correct Answer: Replacing inorganic phosphate and preventing ATP formation at phosphoglycerate kinase

Q25. Which glycolytic intermediate is the precursor for serine biosynthesis?

• 3-Phosphoglycerate
• Phosphoenolpyruvate
• Pyruvate
• Fructose-6-phosphate

Correct Answer: 3-Phosphoglycerate

Q26. Which glycolytic enzyme converts glucose-6-phosphate to fructose-6-phosphate and is freely reversible?

• Phosphoglucose isomerase
• Hexokinase
• Phosphofructokinase-1
• Glucokinase

Correct Answer: Phosphoglucose isomerase

Q27. Which glycolytic intermediate has the highest phosphoryl-transfer potential and donates a phosphate to ADP to form ATP via pyruvate kinase?

• 1,3-Bisphosphoglycerate
• Phosphoenolpyruvate (PEP)
• 3-Phosphoglycerate
• Glucose-6-phosphate

Correct Answer: Phosphoenolpyruvate (PEP)

Q28. Which enzyme catalyzes the reversible conversion of 3-phosphoglycerate to 2-phosphoglycerate?

• Phosphoglycerate mutase
• Phosphoglycerate kinase
• Enolase
• Hexokinase

Correct Answer: Phosphoglycerate mutase

Q29. Which of the following best describes the role of fructose-2,6-bisphosphate in glycolysis?

• Allosteric inhibitor of phosphofructokinase-1
• Allosteric activator of phosphofructokinase-1 enhancing glycolysis
• Direct substrate for ATP synthesis
• Inhibitor of lactate dehydrogenase

Correct Answer: Allosteric activator of phosphofructokinase-1 enhancing glycolysis

Q30. Which glycolytic enzyme deficiency is commonly associated with chronic hemolytic anemia?

• Hexokinase deficiency
• Pyruvate kinase deficiency
• Enolase deficiency
• Aldolase deficiency

Correct Answer: Pyruvate kinase deficiency

Q31. Enolase catalyzes which conversion in glycolysis, and what small molecule is produced during this reaction?

• 3-PG → 2-PG, producing ATP
• 2-PG → PEP, producing water
• PEP → pyruvate, producing CO2
• G6P → F6P, producing NADH

Correct Answer: 2-PG → PEP, producing water

Q32. Which intermediate can be diverted to the pentose phosphate pathway for NADPH and ribose-5-phosphate production?

• 3-Phosphoglycerate
• Fructose-1,6-bisphosphate
• Glucose-6-phosphate
• Phosphoenolpyruvate

Correct Answer: Glucose-6-phosphate

Q33. Which enzymatic reaction in glycolysis directly produces NADH?

• Phosphoglycerate kinase reaction
• Glyceraldehyde-3-phosphate dehydrogenase reaction
• Pyruvate kinase reaction
• Hexokinase reaction

Correct Answer: Glyceraldehyde-3-phosphate dehydrogenase reaction

Q34. In red blood cells, the conversion of 1,3-BPG to 2,3-BPG by bisphosphoglycerate mutase has which physiological effect?

• Increases hemoglobin oxygen affinity
• Decreases hemoglobin oxygen affinity facilitating oxygen release
• Converts lactate to pyruvate
• Generates additional ATP via substrate-level phosphorylation

Correct Answer: Decreases hemoglobin oxygen affinity facilitating oxygen release

Q35. Which statement correctly describes the effect of insulin on hepatic glycolysis?

• Insulin decreases fructose-2,6-bisphosphate levels and inhibits PFK-1
• Insulin increases fructose-2,6-bisphosphate levels and stimulates PFK-1
• Insulin activates gluconeogenesis enzymes directly
• Insulin inhibits hexokinase irreversibly

Correct Answer: Insulin increases fructose-2,6-bisphosphate levels and stimulates PFK-1

Q36. Which enzyme catalyzes a reaction that directly requires inorganic phosphate (Pi) as a substrate?

• Phosphoglycerate kinase
• Glyceraldehyde-3-phosphate dehydrogenase
• Hexokinase
• Enolase

Correct Answer: Glyceraldehyde-3-phosphate dehydrogenase

Q37. The overall free energy change (ΔG) for glycolysis under cellular conditions is:

• Positive, so the pathway is non-spontaneous
• Approximately zero, at equilibrium
• Negative, making the pathway overall exergonic and favorable
• Undefined because glycolysis does not involve energy changes

Correct Answer: Negative, making the pathway overall exergonic and favorable

Q38. During intense exercise when oxygen is limited, regenerating NAD+ for continued glycolysis is accomplished mainly by:

• Oxidation of NADH in mitochondria via the electron transport chain
• Conversion of pyruvate to lactate by lactate dehydrogenase
• Conversion of pyruvate to acetyl-CoA by pyruvate dehydrogenase
• Export of NADH from the cell

Correct Answer: Conversion of pyruvate to lactate by lactate dehydrogenase

Q39. Which glycolytic enzyme cleaves fructose-1,6-bisphosphate into two triose phosphates?

• Triose phosphate isomerase
• Aldolase
• Phosphofructokinase-1
• Hexokinase

Correct Answer: Aldolase

Q40. Which statement about hexokinase vs glucokinase is correct?

• Both hexokinase and glucokinase have the same Km and are inhibited by glucose-6-phosphate
• Hexokinase has low Km and is inhibited by glucose-6-phosphate; glucokinase has high Km and is not inhibited by glucose-6-phosphate
• Glucokinase is present in muscle and inhibited by G6P
• Hexokinase is only found in the liver and is not inhibited by G6P

Correct Answer: Hexokinase has low Km and is inhibited by glucose-6-phosphate; glucokinase has high Km and is not inhibited by glucose-6-phosphate

Q41. In yeast under anaerobic conditions, glycolysis is followed by fermentation producing:

• Lactate only
• Ethanol and CO2
• Acetyl-CoA and water
• Glycerol and oxygen

Correct Answer: Ethanol and CO2

Q42. Which intermediate is a branch point feeding into glycogen synthesis and the pentose phosphate pathway?

• Fructose-1,6-bisphosphate
• Glucose-6-phosphate
• 2-Phosphoglycerate
• Phosphoenolpyruvate

Correct Answer: Glucose-6-phosphate

Q43. Which glycolytic enzyme’s activity is increased by dephosphorylation in response to insulin in the liver?

• Phosphofructokinase-1
• Pyruvate kinase
• Hexokinase IV (glucokinase)
• Glyceraldehyde-3-phosphate dehydrogenase

Correct Answer: Pyruvate kinase

Q44. Which molecule acts as an indicator of high cellular energy charge and inhibits glycolysis?

• AMP
• Fructose-2,6-bisphosphate
• ATP
• ADP

Correct Answer: ATP

Q45. The conversion of phosphoenolpyruvate to pyruvate yields ATP via which mechanism?

• Oxidative phosphorylation
• Substrate-level phosphorylation
• Photophosphorylation
• Electron transport chain coupling

Correct Answer: Substrate-level phosphorylation

Q46. Which enzyme catalyzes a reversible isomerization required to interconvert an aldose and ketose form early in glycolysis?

• Hexokinase
• Phosphoglucose isomerase
• Phosphofructokinase-1
• Pyruvate kinase

Correct Answer: Phosphoglucose isomerase

Q47. Which glycolytic enzyme is responsible for forming ATP directly from ADP during the conversion of 1,3-BPG to 3-PG?

• Glyceraldehyde-3-phosphate dehydrogenase
• Phosphoglycerate kinase
• Pyruvate kinase
• Enolase

Correct Answer: Phosphoglycerate kinase

Q48. Which metabolic fate of pyruvate links glycolysis to the TCA cycle under aerobic conditions?

• Reduction to lactate by lactate dehydrogenase
• Carboxylation to oxaloacetate exclusively
• Oxidative decarboxylation to acetyl-CoA by pyruvate dehydrogenase
• Conversion to ethanol by pyruvate decarboxylase

Correct Answer: Oxidative decarboxylation to acetyl-CoA by pyruvate dehydrogenase

Q49. Which two molecular products primarily store the chemical energy released during glycolysis?

• CO2 and H2O
• ATP and NADH
• FADH2 and acetyl-CoA
• Glycerol and free fatty acids

Correct Answer: ATP and NADH

Q50. In which cellular compartment does glycolysis occur?

• Mitochondrial matrix
• Endoplasmic reticulum
• Cytosol
• Golgi apparatus

Correct Answer: Cytosol

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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