Glycolysis Practice Questions
20 free Glycolysis practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
The scheme of glycolysis was given by which group of scientists?
- A Calvin, Benson, and Bassham
- B Embden, Meyerhof, and Parnas
- C Watson, Crick, and Wilkins
- D Hatch, Slack, and Kortschak
Correct answer: Embden, Meyerhof, and Parnas
Glycolysis is often referred to as the EMP pathway, named after Gustav Embden, Otto Meyerhof, and Jakub Parnas. They were the primary researchers who elucidated the sequence of enzymatic reactions in the cytosol.
In which part of the cell does glycolysis occur in both aerobic and anaerobic organisms?
- A Cytoplasm (cytosol)
- B Mitochondrial matrix
- C Inner mitochondrial membrane
- D Cytoplasmic peroxisomes
Correct answer: Cytoplasm (cytosol)
Glycolysis occurs in the cytoplasm (cytosol) of the cell and does not require any membrane-bound organelles. It is therefore the common initial pathway for both aerobic and anaerobic respiration.
Sucrose is converted into glucose and fructose by the enzyme:
- A Zymase
- B Invertase
- C Hexokinase
- D Phosphofructokinase
Correct answer: Invertase
In plants, sucrose is the end product of photosynthesis and is converted into the monosaccharides glucose and fructose by the enzyme invertase. These two sugars then enter the glycolytic pathway.
During the 'preparatory phase' of glycolysis, how many ATP molecules are consumed for one molecule of glucose?
- A 1
- B 2
- C 3
- D 4
Correct answer: 2
Two molecules of ATP are used during the phosphorylation steps of glycolysis. Specifically, they are used in the conversion of glucose to glucose-6-phosphate and fructose-6-phosphate to fructose-1,6-bisphosphate.
Which enzyme catalyzes the phosphorylation of glucose to glucose-6-phosphate?
- A Phosphofructokinase
- B Pyruvate kinase
- C Hexokinase
- D Enolase
Correct answer: Hexokinase
Hexokinase is the enzyme that initiates glycolysis by phosphorylating glucose at the expense of one ATP molecule. This step traps the glucose molecule inside the cell as a charged phosphate ester.
Fructose-1,6-bisphosphate splits into two 3-carbon compounds. These are:
- A PGA and DHAP
- B BPGA and PGAL
- C PGAL and DHAP
- D PEP and PGA
Correct answer: PGAL and DHAP
The 6-carbon molecule fructose-1,6-bisphosphate is cleaved by the enzyme aldolase into two 3-carbon isomers: glyceraldehyde-3-phosphate (PGAL) and dihydroxyacetone phosphate (DHAP).
In the payoff phase of glycolysis, NAD+ is reduced to NADH + H+ during the conversion of:
- A Glucose to Glucose-6-phosphate
- B BPGA to 3-PGA
- C PGAL to BPGA
- D PEP to Pyruvic acid
Correct answer: PGAL to BPGA
During the oxidation of 3-phosphoglyceraldehyde (PGAL) to 1,3-bisphosphoglycerate (BPGA), electrons are transferred to NAD+. This step is essential for the subsequent generation of ATP.
How many total molecules of ATP are directly synthesized (gross yield) from one molecule of glucose during glycolysis?
- A 2
- B 4
- C 36
- D 38
Correct answer: 4
A total of four ATP molecules are produced via substrate-level phosphorylation (two from each of the two triose molecules). However, the net gain is only two ATP because two were consumed in the preparatory phase.
What is the end product of glycolysis?
- A Acetyl-CoA (2C)
- B Citric acid (6C)
- C Pyruvic acid
- D Lactic acid (3C)
Correct answer: Pyruvic acid
Glycolysis breaks down one molecule of glucose into two molecules of pyruvic acid. This 3-carbon organic acid then serves as the starting point for either fermentation or the Krebs cycle.
The conversion of PEP (phosphoenolpyruvate) to pyruvic acid results in the production of:
- A Hexokinase (HK-1)
- B Phosphofructokinase
- C Aldolase (ALDO)
- D Pyruvate kinase (PK)
Correct answer: Phosphofructokinase
Phosphofructokinase (PFK) is the primary regulatory enzyme because it catalyzes the irreversible rate-limiting step. It is allosterically inhibited by high levels of ATP and citrate.
Which of the following is the key 'regulatory' or 'pacemaker' enzyme of glycolysis?
- A Hexokinase
- B Phosphofructokinase
- C Aldolase
- D Pyruvate kinase
Correct answer: Phosphofructokinase
Phosphofructokinase (PFK) is the primary regulatory enzyme because it catalyzes the irreversible rate-limiting step. It is allosterically inhibited by high levels of ATP and citrate.
During the dehydration step of glycolysis, 2-phosphoglycerate is converted to phosphoenolpyruvate (PEP) by which enzyme?
- A Mutase
- B Isomerase
- C Enolase
- D Dehydrogenase
Correct answer: Enolase
Enolase catalyzes the removal of a water molecule from 2-phosphoglycerate to form the high-energy compound phosphoenolpyruvate (PEP). This step prepares the molecule for the final ATP-generating reaction.
Which molecule is known as the 'mobile electron carrier' that is reduced during glycolysis and carries electrons to the ETC in aerobic respiration?
- A ATP
- B FAD
- C NAD+
- D Coenzyme Q
Correct answer: NAD+
NAD+ (Nicotinamide Adenine Dinucleotide) acts as an oxidizing agent in glycolysis, picking up two electrons and a proton to become NADH. In aerobic conditions, this NADH is then shuttled toward the mitochondria for oxidative phosphorylation.
In the absence of oxygen, what is the fate of the NADH produced in glycolysis?
- A It is converted to ATP directly in the cytoplasm.
- B It donates electrons to pyruvate or acetaldehyde in fermentation.
- C It accumulates in the cell vacuole.
- D It is oxidized to CO2 and water immediately.
Correct answer: It donates electrons to pyruvate or acetaldehyde in fermentation.
In anaerobic conditions, NADH must be re-oxidized to NAD+ to allow glycolysis to continue. This is achieved by donating electrons to pyruvate (forming lactic acid) or acetaldehyde (forming ethanol).
What is the net gain of ATP molecules for every one molecule of glucose undergoing glycolysis?
- A 1
- B 2
- C 4
- D 8
Correct answer: 2
Although four ATP molecules are produced, two ATP molecules are consumed in the early stages (steps 1 and 3). Therefore, the net metabolic gain is 2 ATP molecules per glucose molecule.
Which step in glycolysis involves the use of inorganic phosphate (Pi) rather than ATP?
- A Glucose → Glucose-6-P
- B Fructose-6-P → Fructose-1,6-bisphosphate
- C PGAL → 1,3-BPGA (using Pi)
- D PEP → Pyruvate
Correct answer: PGAL → 1,3-BPGA (using Pi)
The conversion of glyceraldehyde-3-phosphate (PGAL) to 1,3-bisphosphoglycerate (BPGA) uses inorganic phosphate from the cytosol. This is an oxidation-coupled phosphorylation step.
How many molecules of pyruvic acid are produced from the complete glycolysis of three molecules of glucose?
- A 2
- B 3
- C 6
- D 12
Correct answer: 6
Since one molecule of glucose produces two molecules of pyruvic acid, three molecules of glucose will yield $3 imes 2 = 6$ molecules of pyruvic acid.
Which of the following describes the nature of the glycolysis pathway?
- A Strictly aerobic only
- B Strictly anaerobic only
- C Oxygen-independent
- D Requires CO2 input
Correct answer: Oxygen-independent
Glycolysis is oxygen-independent, meaning it can occur whether oxygen is present or not. It is the only pathway for ATP production in obligate anaerobes.
The conversion of 3-phosphoglyceric acid (3-PGA) to 2-phosphoglyceric acid (2-PGA) is a/an:
- A Oxidation
- B Reduction
- C Isomerization
- D Decarboxylation
Correct answer: Isomerization
The enzyme phosphoglyceromutase shifts the phosphate group from the 3rd carbon to the 2nd carbon. This is an isomerization reaction that rearranges the molecule without changing its chemical formula.
Which of the following is NOT produced during glycolysis?
- A ATP
- B NADH + H+
- C Pyruvic acid
- D FADH2
Correct answer: FADH2
FADH2 is only produced during the Krebs Cycle (TCA cycle) in the mitochondrial matrix. Glycolysis only produces ATP, NADH, and pyruvic acid.