Glycolysis – Complete Notes for OSSTET
1. Introduction
Glycolysis is the first step of cellular respiration (both aerobic and anaerobic).
Occurs in the cytoplasm of all living cells.
It is the breakdown of one molecule of glucose (6C) into two molecules of pyruvate (3C each).
First discovered by Embden, Meyerhof, and Parnas → also called EMP pathway.
2. Location
Cytoplasm of the cell.
Present in all organisms (plants, animals, microorganisms).
3. Steps of Glycolysis
Glycolysis occurs in 10 enzyme-controlled steps, divided into two phases:
A. Energy Investment Phase (Steps 1–5)
Uses 2 ATP molecules.
Glucose → Glucose-6-phosphate (G6P)
Enzyme: Hexokinase (or Glucokinase in liver)
ATP consumed.
Function: traps glucose inside cell.
G6P → Fructose-6-phosphate (F6P)
Enzyme: Phosphoglucose isomerase.
F6P → Fructose-1,6-bisphosphate (F1,6BP)
Enzyme: Phosphofructokinase-1 (PFK-1)
ATP consumed (rate-limiting step of glycolysis).
F1,6BP → Glyceraldehyde-3-phosphate (G3P) + Dihydroxyacetone phosphate (DHAP)
Enzyme: Aldolase.
DHAP ⇌ G3P
Enzyme: Triose phosphate isomerase.
Result: Two molecules of G3P enter next phase.
B. Energy Payoff Phase (Steps 6–10)
Produces 4 ATP and 2 NADH.
G3P → 1,3-Bisphosphoglycerate (1,3BPG)
Enzyme: G3P dehydrogenase.
NAD⁺ reduced to NADH.
1,3BPG → 3-Phosphoglycerate (3PG)
Enzyme: Phosphoglycerate kinase.
ATP generated (substrate-level phosphorylation).
3PG → 2-Phosphoglycerate (2PG)
Enzyme: Phosphoglycerate mutase.
2PG → Phosphoenolpyruvate (PEP)
Enzyme: Enolase.
PEP → Pyruvate
Enzyme: Pyruvate kinase.
ATP generated.
4. Net Gain of Glycolysis
From 1 molecule of glucose:
ATP used: 2
ATP gained: 4
Net ATP: 2
NADH formed: 2 (→ yields ATP in electron transport chain under aerobic condition).
Final Products:
2 Pyruvate
2 NADH
2 Net ATP
5. Fate of Pyruvate
Depends on oxygen availability:
Aerobic (with O₂):
Pyruvate enters mitochondria → oxidized in Krebs cycle → complete breakdown into CO₂ + H₂O.
Anaerobic (without O₂):
In animals: Pyruvate → Lactic acid (via lactate dehydrogenase).
In plants & yeast: Pyruvate → Ethanol + CO₂ (alcoholic fermentation).
6. Regulation of Glycolysis
Key regulatory enzymes:
Hexokinase – inhibited by G6P.
PFK-1 – rate-limiting enzyme; activated by AMP/ADP, inhibited by ATP & citrate.
Pyruvate kinase – activated by F1,6BP; inhibited by ATP & alanine.
7. Significance of Glycolysis
Provides quick energy (2 ATP per glucose).
Supplies pyruvate for further energy production (Krebs cycle).
Provides intermediates for biosynthetic pathways (amino acids, glycerol, fatty acids).
Operates in both aerobic and anaerobic organisms.
8. Important MCQ Points for OSSTET
Glycolysis → cytoplasm.
Also called EMP pathway.
Rate-limiting enzyme → PFK-1.
Net gain → 2 ATP + 2 NADH.
Anaerobic end products → Lactic acid (animals), Ethanol + CO₂ (yeast/plants).
Number of steps → 10 enzyme-catalyzed reactions.
MCQs on Glycolysis (Set – 1)
1. Glycolysis occurs in which part of the cell?
a) Mitochondria
b) Cytoplasm
c) Chloroplast
d) Nucleus
Answer: b) Cytoplasm
Explanation: Glycolysis takes place in the cytoplasm of all living cells, independent of organelles.
2. Who discovered the glycolysis pathway?
a) Calvin
b) Embden, Meyerhof, and Parnas
c) Kreb
d) Warburg
Answer: b) Embden, Meyerhof, and Parnas
Explanation: Hence glycolysis is also called the EMP pathway.
3. Glycolysis breaks down one molecule of glucose into ____ molecules of pyruvate.
a) 1
b) 2
c) 3
d) 4
Answer: b) 2
Explanation: One glucose (6C) is split into two molecules of pyruvate (3C each).
4. Which enzyme converts glucose to glucose-6-phosphate?
a) Hexokinase
b) PFK-1
c) Aldolase
d) Enolase
Answer: a) Hexokinase
Explanation: Hexokinase catalyzes phosphorylation of glucose using ATP.
5. Which enzyme is the rate-limiting step of glycolysis?
a) Hexokinase
b) Pyruvate kinase
c) PFK-1
d) G3P dehydrogenase
Answer: c) PFK-1
Explanation: Phosphofructokinase-1 regulates glycolysis and is inhibited by ATP and citrate.
6. How many ATP molecules are consumed in the preparatory phase of glycolysis?
a) 1
b) 2
c) 3
d) 4
Answer: b) 2
Explanation: Two ATP are invested at steps 1 and 3.
7. How many net ATP are gained in glycolysis?
a) 1
b) 2
c) 4
d) 6
Answer: b) 2
Explanation: Total 4 ATP are produced, but 2 are used → Net gain = 2.
8. Which coenzyme is reduced during glycolysis?
a) NAD⁺
b) FAD
c) NADP⁺
d) CoA
Answer: a) NAD⁺
Explanation: Two molecules of NAD⁺ are reduced to NADH at G3P dehydrogenase step.
9. The end products of glycolysis are:
a) CO₂ + H₂O
b) 2 pyruvate + 2 NADH + 2 ATP
c) 2 pyruvate + 2 FADH₂
d) 2 acetyl-CoA
Answer: b) 2 pyruvate + 2 NADH + 2 ATP
Explanation: These are the direct products of glycolysis.
10. In absence of oxygen, pyruvate is converted into ____ in animals.
a) Ethanol
b) Lactic acid
c) Acetyl-CoA
d) CO₂
Answer: b) Lactic acid
Explanation: Anaerobic respiration in muscles converts pyruvate into lactic acid.
11. In absence of oxygen, pyruvate is converted into ____ in yeast.
a) Lactic acid
b) Acetyl-CoA
c) Ethanol + CO₂
d) Oxaloacetate
Answer: c) Ethanol + CO₂
Explanation: Yeast fermentation produces alcohol and carbon dioxide.
12. Which enzyme splits fructose-1,6-bisphosphate into G3P and DHAP?
a) Aldolase
b) Triose phosphate isomerase
c) Enolase
d) Pyruvate kinase
Answer: a) Aldolase
Explanation: Aldolase splits F1,6BP into two 3C sugars.
13. Number of enzyme-controlled steps in glycolysis is:
a) 8
b) 9
c) 10
d) 12
Answer: c) 10
Explanation: Glycolysis consists of 10 enzyme-catalyzed reactions.
14. Which reaction in glycolysis produces NADH?
a) Hexokinase step
b) G3P → 1,3-BPG
c) PEP → Pyruvate
d) 3PG → 2PG
Answer: b) G3P → 1,3-BPG
Explanation: Catalyzed by G3P dehydrogenase, reducing NAD⁺ to NADH.
15. Which step produces ATP directly (substrate-level phosphorylation)?
a) G3P → 1,3-BPG
b) 1,3-BPG → 3PG
c) 3PG → 2PG
d) PEP → Pyruvate
Answer: b) and d)
Explanation: ATP is produced in steps catalyzed by phosphoglycerate kinase and pyruvate kinase.
16. Which is the first irreversible step of glycolysis?
a) Hexokinase
b) PFK-1
c) Pyruvate kinase
d) Aldolase
Answer: a) Hexokinase
Explanation: Once glucose is phosphorylated to G6P, it cannot exit the cell.
17. Glycolysis is common to:
a) Only aerobic organisms
b) Only anaerobic organisms
c) Both aerobic and anaerobic organisms
d) Only plants
Answer: c) Both aerobic and anaerobic organisms
Explanation: It occurs in all types of respiration.
18. Net NADH produced per glucose in glycolysis is:
a) 1
b) 2
c) 3
d) 4
Answer: b) 2
Explanation: One NADH per G3P; since two G3P are formed → total 2 NADH.
19. Which enzyme converts DHAP into G3P?
a) Enolase
b) Triose phosphate isomerase
c) Hexokinase
d) Pyruvate kinase
Answer: b) Triose phosphate isomerase
Explanation: Ensures both molecules enter payoff phase.
20. Glycolysis is also known as:
a) TCA cycle
b) Calvin cycle
c) EMP pathway
d) Pentose phosphate pathway
Answer: c) EMP pathway
Explanation: Named after Embden, Meyerhof, and Parnas.
MCQs on Glycolysis (Set – 2)
21. The first step of glycolysis is catalyzed by:
a) Hexokinase
b) Phosphofructokinase
c) Pyruvate kinase
d) Aldolase
Answer: a) Hexokinase
Explanation: It phosphorylates glucose to glucose-6-phosphate using ATP.
22. Which step of glycolysis is reversible?
a) Hexokinase step
b) PFK-1 step
c) Pyruvate kinase step
d) Aldolase step
Answer: d) Aldolase step
Explanation: Aldolase reaction is freely reversible, unlike the committed steps.
23. How many NADH molecules are produced per glucose molecule in glycolysis?
a) 1
b) 2
c) 3
d) 4
Answer: b) 2
Explanation: One NADH per G3P → total 2 per glucose.
24. Which enzyme catalyzes the final step of glycolysis?
a) Enolase
b) Hexokinase
c) Pyruvate kinase
d) Aldolase
Answer: c) Pyruvate kinase
Explanation: Converts PEP to pyruvate with ATP formation.
25. Which step of glycolysis consumes ATP?
a) Hexokinase step
b) PFK-1 step
c) Both (a) and (b)
d) None
Answer: c) Both (a) and (b)
Explanation: Glucose → G6P and F6P → F1,6BP both require ATP.
26. The glycolytic pathway yields how many ATP per glucose in the absence of oxygen?
a) 1
b) 2
c) 4
d) 6
Answer: b) 2
Explanation: Net gain = 2 ATP in anaerobic glycolysis.
27. The enzyme enolase converts:
a) G3P → 1,3-BPG
b) 2PG → PEP
c) PEP → Pyruvate
d) DHAP → G3P
Answer: b) 2PG → PEP
Explanation: Enolase forms phosphoenolpyruvate (PEP).
28. Which step of glycolysis is considered the committed step?
a) Hexokinase
b) PFK-1
c) Aldolase
d) Pyruvate kinase
Answer: b) PFK-1
Explanation: This is highly regulated and commits glucose to glycolysis.
29. Which molecule is formed at the end of the preparatory phase of glycolysis?
a) G6P
b) Pyruvate
c) Two G3P
d) F6P
Answer: c) Two G3P
Explanation: Glucose is split into two glyceraldehyde-3-phosphate molecules.
30. How many steps in glycolysis generate ATP?
a) 1
b) 2
c) 3
d) 4
Answer: b) 2
Explanation: At phosphoglycerate kinase and pyruvate kinase steps.
31. How many steps in glycolysis are irreversible?
a) 1
b) 2
c) 3
d) 4
Answer: c) 3
Explanation: Hexokinase, PFK-1, and pyruvate kinase steps are irreversible.
32. The enzyme phosphoglycerate kinase catalyzes which reaction?
a) G3P → 1,3-BPG
b) 1,3-BPG → 3PG
c) 2PG → PEP
d) PEP → Pyruvate
Answer: b) 1,3-BPG → 3PG
Explanation: This step generates ATP by substrate-level phosphorylation.
33. In glycolysis, how many molecules of pyruvate are formed from one molecule of glucose?
a) 1
b) 2
c) 3
d) 4
Answer: b) 2
Explanation: Each glucose splits into two pyruvates.
34. Which glycolytic enzyme requires Mg²⁺ as a cofactor?
a) Hexokinase
b) PFK-1
c) Pyruvate kinase
d) All of these
Answer: d) All of these
Explanation: Many glycolytic kinases need Mg²⁺ for activity.
35. During anaerobic glycolysis in humans, which enzyme converts pyruvate into lactate?
a) Pyruvate decarboxylase
b) Alcohol dehydrogenase
c) Lactate dehydrogenase
d) Aldolase
Answer: c) Lactate dehydrogenase
Explanation: It regenerates NAD⁺ by reducing pyruvate.
36. The enzyme triose phosphate isomerase interconverts:
a) G6P ↔ F6P
b) DHAP ↔ G3P
c) PEP ↔ Pyruvate
d) 3PG ↔ 2PG
Answer: b) DHAP ↔ G3P
Explanation: Ensures both triose molecules proceed in glycolysis.
37. Which intermediate of glycolysis is a high-energy compound?
a) G6P
b) 1,3-BPG
c) 2PG
d) F6P
Answer: b) 1,3-BPG
Explanation: It has a high phosphoryl transfer potential.
38. Which enzyme converts glucose-6-phosphate to fructose-6-phosphate?
a) Hexokinase
b) Phosphoglucose isomerase
c) Aldolase
d) Triose phosphate isomerase
Answer: b) Phosphoglucose isomerase
Explanation: This is a reversible isomerization step.
39. The energy yield from glycolysis (per glucose) is:
a) 2 ATP + 2 NADH
b) 2 ATP + 4 NADH
c) 4 ATP + 2 FADH₂
d) 6 ATP + 2 NADH
Answer: a) 2 ATP + 2 NADH
Explanation: Net gain is 2 ATP and 2 NADH.
40. Which step in glycolysis produces water (H₂O)?
a) Hexokinase step
b) Enolase step
c) Aldolase step
d) PFK-1 step
Answer: b) Enolase step
Explanation: Enolase converts 2PG → PEP with release of H₂O.
MCQs on Glycolysis (Set – 3)
41. Glycolysis occurs in which part of the cell?
a) Nucleus
b) Cytoplasm
c) Mitochondria
d) Endoplasmic reticulum
Answer: b) Cytoplasm
Explanation: Glycolysis is a cytoplasmic pathway present in almost all cells.
42. Which step of glycolysis is an example of substrate-level phosphorylation?
a) PFK-1 reaction
b) Phosphoglycerate kinase reaction
c) Pyruvate kinase reaction
d) Both (b) and (c)
Answer: d) Both (b) and (c)
Explanation: ATP is directly synthesized at phosphoglycerate kinase and pyruvate kinase steps.
43. Glycolysis is also known as:
a) Cori cycle
b) Krebs cycle
c) EMP pathway
d) Hatch-Slack pathway
Answer: c) EMP pathway
Explanation: Discovered by Embden, Meyerhof, and Parnas.
44. In red blood cells, glycolysis is the only source of:
a) NADPH
b) ATP
c) FADH₂
d) Acetyl-CoA
Answer: b) ATP
Explanation: RBCs lack mitochondria, so ATP comes only from glycolysis.
45. Which glycolytic enzyme is regulated allosterically by ATP and AMP?
a) Aldolase
b) Hexokinase
c) PFK-1
d) Enolase
Answer: c) PFK-1
Explanation: ATP inhibits, AMP activates → controls glycolytic rate.
46. Which ion inhibits the enzyme enolase?
a) Mg²⁺
b) K⁺
c) F⁻ (Fluoride)
d) Ca²⁺
Answer: c) F⁻ (Fluoride)
Explanation: Fluoride inhibits enolase → used in blood glucose preservation.
47. Which of the following is a byproduct of glycolysis?
a) Oxygen
b) Carbon dioxide
c) Water
d) Ammonia
Answer: c) Water
Explanation: One H₂O molecule is released during enolase step.
48. What is the total ATP yield from glycolysis under aerobic conditions?
a) 2
b) 4
c) 6 or 8 (depending on shuttle)
d) 10
Answer: c) 6 or 8
Explanation: 2 ATP (direct) + 2 NADH (converted to 4–6 ATP via ETC).
49. In yeast under anaerobic condition, pyruvate is converted into:
a) Lactate
b) Ethanol + CO₂
c) Acetyl-CoA
d) Citrate
Answer: b) Ethanol + CO₂
Explanation: Alcoholic fermentation occurs in yeast.
50. Which enzyme catalyzes the conversion of phosphoenolpyruvate to pyruvate?
a) Aldolase
b) Pyruvate kinase
c) Enolase
d) Triose phosphate isomerase
Answer: b) Pyruvate kinase
Explanation: Generates 1 ATP per PEP.
51. The main purpose of fermentation following glycolysis is to:
a) Produce more ATP
b) Regenerate NAD⁺
c) Generate FADH₂
d) Increase oxygen
Answer: b) Regenerate NAD⁺
Explanation: Fermentation ensures glycolysis continues without oxygen.
52. Which of the following steps produces NADH in glycolysis?
a) Hexokinase step
b) G3P dehydrogenase step
c) Pyruvate kinase step
d) Aldolase step
Answer: b) G3P dehydrogenase step
Explanation: Each G3P → 1 NADH (total 2 per glucose).
53. The “investment phase” of glycolysis requires:
a) 1 ATP
b) 2 ATP
c) 3 ATP
d) 4 ATP
Answer: b) 2 ATP
Explanation: Glucose → G6P and F6P → F1,6BP use 2 ATP.
54. Which glycolytic intermediate is a precursor for serine biosynthesis?
a) 3-Phosphoglycerate (3PG)
b) Pyruvate
c) PEP
d) G3P
Answer: a) 3-Phosphoglycerate (3PG)
Explanation: 3PG is diverted into amino acid (serine) pathway.
55. How many enzymatic reactions occur in glycolysis?
a) 8
b) 9
c) 10
d) 11
Answer: c) 10
Explanation: Glycolysis has 10 sequential enzymatic steps.
56. Which coenzyme is required in the G3P dehydrogenase step?
a) NAD⁺
b) FAD
c) CoA
d) FMN
Answer: a) NAD⁺
Explanation: Accepts electrons to form NADH.
57. Which glycolytic enzyme deficiency causes hemolytic anemia?
a) Aldolase
b) Pyruvate kinase
c) Enolase
d) Triose phosphate isomerase
Answer: b) Pyruvate kinase
Explanation: RBCs depend solely on glycolysis → ATP shortage causes hemolysis.
58. Which of the following is NOT a glycolytic intermediate?
a) Glucose-6-phosphate
b) Fructose-1,6-bisphosphate
c) Succinyl-CoA
d) Phosphoenolpyruvate
Answer: c) Succinyl-CoA
Explanation: It is a TCA cycle intermediate, not glycolytic.
59. Which step of glycolysis is reversible and near equilibrium?
a) Hexokinase
b) Aldolase
c) PFK-1
d) Pyruvate kinase
Answer: b) Aldolase
Explanation: Many steps are reversible, but control steps are irreversible.
60. The net end products of glycolysis under aerobic conditions are:
a) 2 Pyruvate + 2 ATP + 2 NADH
b) 2 Lactate + 2 ATP
c) 2 Ethanol + 2 ATP + 2 CO₂
d) 6 CO₂ + 6 H₂O
Answer: a) 2 Pyruvate + 2 ATP + 2 NADH
Explanation: Pyruvate enters TCA cycle if oxygen is available.
MCQs on Glycolysis (Set – 4)
61. Which enzyme catalyzes the cleavage of fructose-1,6-bisphosphate?
a) Aldolase
b) Enolase
c) Isomerase
d) Mutase
Answer: a) Aldolase
Explanation: Aldolase splits F-1,6-BP into DHAP and G3P.
62. Which glycolytic enzyme requires Mg²⁺ as a cofactor?
a) Hexokinase
b) Phosphofructokinase
c) Pyruvate kinase
d) All of these
Answer: d) All of these
Explanation: Many kinases in glycolysis require Mg²⁺ for ATP binding.
63. How many pyruvate molecules are formed from one glucose in glycolysis?
a) 1
b) 2
c) 3
d) 4
Answer: b) 2
Explanation: Each glucose (6C) → 2 pyruvate (3C each).
64. Which glycolytic enzyme also functions in gluconeogenesis but in reverse?
a) Hexokinase
b) Phosphoglucose isomerase
c) Pyruvate kinase
d) PFK-1
Answer: b) Phosphoglucose isomerase
Explanation: It is reversible, working both ways.
65. The NADH generated in glycolysis is reoxidized by which shuttle in brain cells?
a) Malate-aspartate shuttle
b) Glycerol phosphate shuttle
c) Citrate shuttle
d) Carnitine shuttle
Answer: a) Malate-aspartate shuttle
Explanation: Brain & liver use malate-aspartate shuttle for NADH transfer.
66. The major rate-limiting step of glycolysis is catalyzed by:
a) Hexokinase
b) PFK-1
c) Aldolase
d) Pyruvate kinase
Answer: b) PFK-1
Explanation: PFK-1 is the key regulatory enzyme of glycolysis.
67. Which glycolytic intermediate enters the pentose phosphate pathway?
a) DHAP
b) F6P
c) PEP
d) Pyruvate
Answer: b) F6P
Explanation: Both F6P and G6P can enter PPP.
68. Which glycolytic intermediate can be used for triglyceride synthesis?
a) DHAP
b) 3PG
c) PEP
d) Pyruvate
Answer: a) DHAP
Explanation: DHAP is converted to glycerol-3-phosphate, a fat precursor.
69. Which step in glycolysis involves isomerization of a ketose to an aldose?
a) G6P → F6P
b) F6P → F1,6BP
c) G3P ↔ DHAP
d) PEP → Pyruvate
Answer: a) G6P → F6P
Explanation: Glucose-6-phosphate (aldose) is converted to fructose-6-phosphate (ketose).
70. In anaerobic glycolysis in muscle, pyruvate is converted into:
a) Lactate
b) Ethanol
c) Acetyl-CoA
d) Malate
Answer: a) Lactate
Explanation: Lactic acid fermentation regenerates NAD⁺.
71. What is the total ATP yield in anaerobic glycolysis?
a) 1 ATP
b) 2 ATP
c) 4 ATP
d) 6 ATP
Answer: b) 2 ATP
Explanation: No NADH is utilized; only 2 ATP are net gained.
72. The enzyme triose phosphate isomerase interconverts:
a) G3P and DHAP
b) G6P and F6P
c) PEP and pyruvate
d) 2PG and 3PG
Answer: a) G3P and DHAP
Explanation: Ensures that both products of aldolase can proceed in glycolysis.
73. The first irreversible step of glycolysis is catalyzed by:
a) Hexokinase
b) PFK-1
c) Pyruvate kinase
d) Aldolase
Answer: a) Hexokinase
Explanation: Hexokinase traps glucose inside the cell as G6P.
74. Which of the following can bypass glycolysis completely?
a) Neurons
b) Erythrocytes
c) Liver
d) None
Answer: c) Liver
Explanation: Liver can use fatty acid oxidation and gluconeogenesis instead.
75. Which glycolytic intermediate directly enters the TCA cycle after conversion to Acetyl-CoA?
a) PEP
b) Pyruvate
c) 3PG
d) DHAP
Answer: b) Pyruvate
Explanation: Pyruvate → Acetyl-CoA (via PDH) → TCA cycle.
76. Which step of glycolysis releases water?
a) Aldolase
b) Enolase
c) PFK-1
d) Hexokinase
Answer: b) Enolase
Explanation: Converts 2PG → PEP with release of H₂O.
77. How many NADH are produced per glucose in glycolysis?
a) 1
b) 2
c) 3
d) 4
Answer: b) 2
Explanation: Each G3P → 1 NADH; 2 G3P molecules give 2 NADH.
78. Which glycolytic enzyme is inhibited by arsenate?
a) G3P dehydrogenase
b) Pyruvate kinase
c) Aldolase
d) Enolase
Answer: a) G3P dehydrogenase
Explanation: Arsenate prevents ATP production at this step.
79. Which glycolytic enzyme deficiency leads to hereditary hemolytic anemia other than pyruvate kinase?
a) Hexokinase
b) G3P dehydrogenase
c) PFK-1
d) Enolase
Answer: a) Hexokinase
Explanation: Rare deficiency reduces ATP → RBC damage.
80. The conversion of glucose to lactate in muscle is known as:
a) Alcoholic fermentation
b) Lactic acid fermentation
c) Oxidative phosphorylation
d) Glycogenesis
Answer: b) Lactic acid fermentation
Explanation: Anaerobic process producing lactate from glucose.
MCQs on Glycolysis (Set – 5: Q.81–100)
81. Which enzyme catalyzes the final step of glycolysis?
a) Hexokinase
b) PFK-1
c) Pyruvate kinase
d) Enolase
Answer: c) Pyruvate kinase
Explanation: Converts PEP → Pyruvate, producing ATP.
82. The Pasteur effect refers to:
a) Inhibition of glycolysis by oxygen
b) Enhancement of glycolysis by oxygen
c) Anaerobic breakdown of glucose
d) ATP synthesis in mitochondria
Answer: a) Inhibition of glycolysis by oxygen
Explanation: Aerobic conditions suppress glycolysis due to efficient ATP from respiration.
83. In yeast, anaerobic glycolysis produces:
a) Lactate
b) Ethanol + CO₂
c) Acetyl-CoA
d) Oxaloacetate
Answer: b) Ethanol + CO₂
Explanation: Alcoholic fermentation is carried out by yeast.
84. The Cori cycle connects glycolysis in muscle with:
a) Liver gluconeogenesis
b) Brain metabolism
c) Fatty acid oxidation
d) Pentose phosphate pathway
Answer: a) Liver gluconeogenesis
Explanation: Lactate from muscle is transported to liver → glucose.
85. Which vitamin-derived coenzyme is required in glycolysis?
a) Thiamine (B1)
b) Niacin (B3)
c) Riboflavin (B2)
d) Pyridoxine (B6)
Answer: b) Niacin (B3)
Explanation: Niacin forms NAD⁺, required in G3P dehydrogenase step.
86. The Warburg effect describes:
a) Increased glycolysis in cancer cells even with oxygen
b) Inhibition of glycolysis in tumors
c) Anaerobic glycolysis in muscles
d) ATP generation in mitochondria
Answer: a) Increased glycolysis in cancer cells even with oxygen
Explanation: Cancer cells rely heavily on aerobic glycolysis.
87. In glycolysis, which molecule acts as an allosteric activator of PFK-1?
a) ATP
b) Citrate
c) AMP
d) NADH
Answer: c) AMP
Explanation: AMP indicates low energy and activates PFK-1.
88. Pyruvate kinase is activated by:
a) ATP
b) F1,6BP
c) Citrate
d) NADH
Answer: b) F1,6BP
Explanation: This is a feed-forward activation mechanism.
89. The energy investment phase of glycolysis uses:
a) 1 ATP
b) 2 ATP
c) 3 ATP
d) 4 ATP
Answer: b) 2 ATP
Explanation: 1 ATP used by hexokinase, 1 ATP by PFK-1.
90. The energy payoff phase of glycolysis yields:
a) 2 ATP + 1 NADH
b) 4 ATP + 2 NADH
c) 4 ATP + 4 NADH
d) 2 ATP + 2 NADH
Answer: b) 4 ATP + 2 NADH
Explanation: From two G3P molecules → 4 ATP, 2 NADH.
91. Which enzyme deficiency is the most common cause of hereditary hemolytic anemia?
a) Hexokinase
b) Pyruvate kinase
c) PFK-1
d) Enolase
Answer: b) Pyruvate kinase
Explanation: RBCs depend on glycolysis for ATP; deficiency causes hemolysis.
92. Which step in glycolysis is an example of substrate-level phosphorylation?
a) Hexokinase
b) Pyruvate kinase
c) PFK-1
d) Phosphoglucose isomerase
Answer: b) Pyruvate kinase
Explanation: PEP → Pyruvate produces ATP directly.
93. Which intermediate is the highest-energy compound in glycolysis?
a) 1,3-BPG
b) PEP
c) 2PG
d) F1,6BP
Answer: b) PEP
Explanation: PEP has very high phosphoryl transfer potential.
94. Which intermediate in glycolysis is used in amino acid (serine) synthesis?
a) 3PG
b) Pyruvate
c) DHAP
d) F6P
Answer: a) 3PG
Explanation: 3-Phosphoglycerate is precursor for serine biosynthesis.
95. Which enzyme converts glucose to glucose-6-phosphate?
a) Hexokinase
b) PFK-1
c) Aldolase
d) Isomerase
Answer: a) Hexokinase
Explanation: First irreversible step in glycolysis.
96. Which enzyme produces NADH during glycolysis?
a) Hexokinase
b) Pyruvate kinase
c) G3P dehydrogenase
d) Enolase
Answer: c) G3P dehydrogenase
Explanation: G3P → 1,3-BPG produces NADH.
97. Which molecule inhibits hexokinase?
a) Glucose-6-phosphate
b) ATP
c) Citrate
d) Fructose-2,6-bisphosphate
Answer: a) Glucose-6-phosphate
Explanation: Product inhibition ensures no waste of glucose.
98. Which of the following is a reversible reaction in glycolysis?
a) Hexokinase
b) PFK-1
c) Aldolase
d) Pyruvate kinase
Answer: c) Aldolase
Explanation: Aldolase step is reversible; key regulatory steps are irreversible.
99. The total ATP yield from glycolysis under aerobic condition is:
a) 2
b) 4
c) 6–8
d) 10
Answer: c) 6–8
Explanation: 2 ATP + 2 NADH (→ 4–6 ATP via ETC) = 6–8 ATP total.
100. Glycolysis occurs in which part of the cell?
a) Nucleus
b) Cytoplasm
c) Mitochondria
d) Endoplasmic reticulum
Answer: b) Cytoplasm
Explanation: Entire glycolysis pathway takes place in cytosol.
