Respiration – Glycolysis: NEET MCQs with Answers

15 free questions on Respiration – Glycolysis for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

Syllabus covered: Glycolysis

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Question 1

Previous-year question
In plants, the enzyme invertase splits sucrose into two monosaccharides, both of which then enter glycolysis. Which are these monosaccharides? [NEET (Sawaimadhopur) 2024]
  1. Glucose and fructose
  2. Glucose and galactose
  3. Fructose and galactose
  4. Glucose and glucose
Show answer
Answer: (A) Glucose and fructose
Explanation: Sucrose is hydrolysed by invertase into glucose and fructose, both of which are phosphorylated and enter the glycolytic pathway. Galactose is a product of lactose hydrolysis, and two glucose molecules come from maltose.

Question 2

Previous-year question
During glycolysis, the conversion of 1,3-bisphosphoglyceric acid into 3-phosphoglyceric acid is best described as: [NEET (Sawaimadhopur) 2024]
  1. Energy utilising process
  2. Phosphorylation process
  3. Isomerisation process
  4. Energy yielding process
Show answer
Answer: (D) Energy yielding process
Explanation: Conversion of 1,3-bisphosphoglyceric acid (BPGA) to 3-phosphoglyceric acid (PGA) is an energy-yielding step in which one ATP is formed by substrate-level phosphorylation. It does not consume ATP, it is a dephosphorylation of the substrate rather than its phosphorylation, and it is not an isomerisation.

Question 3

Previous-year question
Assertion: ATP is utilised at two steps in glycolysis. [NEET 2023]
Reason: The first ATP is used to convert glucose into glucose-6-phosphate and the second ATP is used to convert fructose-6-phosphate into fructose-1,6-diphosphate.
  1. Both A and R are true but R is NOT the correct explanation of A.
  2. A is true but R is false.
  3. A is false but R is true.
  4. Both A and R are true and R is the correct explanation of A.
Show answer
Answer: (D) Both A and R are true and R is the correct explanation of A.
Explanation: Assertion is true: ATP is consumed at two steps of glycolysis. Reason is also true and explains it: one ATP is used to phosphorylate glucose to glucose-6-phosphate (hexokinase) and another to convert fructose-6-phosphate to fructose-1,6-bisphosphate (phosphofructokinase).

Question 4

Previous-year question
In glycolysis, ATP is produced during which of the following conversions? [NEET (Paper-2) 2021]
  1. Glucose to glucose 6-phosphate
  2. Fructose 6-phosphate to fructose 1,6-bisphosphate
  3. 1,3-bisphosphoglyceric acid to 3-phosphoglyceric acid
  4. Both fructose 6-phosphate to fructose 1,6-bisphosphate and 1,3-bisphosphoglyceric acid to 3-phosphoglyceric acid
Show answer
Answer: (C) 1,3-bisphosphoglyceric acid to 3-phosphoglyceric acid
Explanation: ATP is formed by substrate-level phosphorylation when 1,3-bisphosphoglyceric acid (BPGA) is converted to 3-phosphoglyceric acid, and again when PEP is converted to pyruvic acid. The conversions of glucose to glucose 6-phosphate and of fructose 6-phosphate to fructose 1,6-bisphosphate consume ATP instead of producing it.

Question 5

Previous-year question
The conversion of glucose to glucose-6-phosphate, the first irreversible reaction of glycolysis, is catalysed by [NEET 2019]
  1. aldolase
  2. hexokinase
  3. enolase
  4. phosphofructokinase
Show answer
Answer: (B) hexokinase
Explanation: Hexokinase catalyses this priming reaction using one molecule of ATP. Being irreversible, it traps the sugar within the cell and commits it to glycolysis; phosphofructokinase catalyses the second, later phosphorylation.

Question 6

Previous-year question
The incomplete oxidation of glucose into pyruvic acid through several intermediate steps is known as [AIPMT 1988]
  1. TCA pathway
  2. glycolysis
  3. HMS pathway
  4. Krebs' cycle
Show answer
Answer: (B) glycolysis
Explanation: Glycolysis is the process in which glucose is only partially (incompletely) oxidised to pyruvic acid through a series of ten enzyme-catalysed intermediate steps in the cytoplasm. Complete oxidation to CO₂ and water occurs later, in the Krebs' cycle and electron transport chain.

Question 7

Previous-year question
The EMP pathway can produce a total of [AIPMT 1990]
  1. 6 ATP
  2. 8 ATP
  3. 24 ATP
  4. 38 ATP
Show answer
Answer: (B) 8 ATP
Explanation: EMP (Embden–Meyerhof–Parnas) pathway is another name for glycolysis. It yields 2 NADH (worth 2 × 3 = 6 ATP when oxidised through the ETC) plus a net 2 ATP by substrate-level phosphorylation, giving a total energy value of 8 ATP.
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Question 8

Previous-year question
The end product of glycolysis is [AIPMT 1990]
  1. acetyl Co-A
  2. pyruvic acid
  3. glucose 1-phosphate
  4. fructose 1-phosphate
Show answer
Answer: (B) pyruvic acid
Explanation: Glycolysis ends with pyruvic acid. One molecule of glucose is broken down in the cytoplasm into two molecules of pyruvic acid. Acetyl Co-A is formed subsequently, by the oxidative decarboxylation of pyruvate, and marks the link reaction rather than the end of glycolysis.

Question 9

Previous-year question
In animal cells, the first stage of glucose breakdown is [AIPMT 1994]
  1. Krebs' cycle
  2. glycolysis
  3. oxidative phosphorylation
  4. ETC
Show answer
Answer: (B) glycolysis
Explanation: Glycolysis is the first stage of glucose breakdown and takes place in the cytoplasm. It is the sequence of reactions in which glucose is degraded anaerobically to pyruvic acid, with a net gain of 2 ATP. Being independent of oxygen, it is the common pathway for both aerobic and anaerobic respiration.

Question 10

Previous-year question
During the oxidation step of glycolysis, electrons are removed by [AIPMT 2004]
  1. ATP
  2. glyceraldehyde-3-phosphate
  3. NAD⁺
  4. molecular oxygen
Show answer
Answer: (C) NAD⁺
Explanation: NAD⁺ acts as the electron acceptor during glycolysis. When glyceraldehyde-3-phosphate is oxidised to 1,3-bisphosphoglycerate, NAD⁺ removes the electrons (as a hydride ion) and is itself reduced to NADH + H⁺. Molecular oxygen is not involved at any stage of glycolysis.

Question 11

Previous-year question
The conversion of glucose to glucose-6-phosphate, the first irreversible reaction of glycolysis, is catalysed by [NEET (National) 2019]
  1. hexokinase
  2. enolase
  3. phosphofructokinase
  4. aldolase
Show answer
Answer: (A) hexokinase
Explanation: Hexokinase catalyses the phosphorylation of glucose to glucose-6-phosphate using one ATP. It is the first step of the activation (preparatory) phase of glycolysis and is essentially irreversible, effectively committing the glucose molecule to the pathway by trapping it inside the cell.

Question 12

Previous-year question
Given below are two statements, one labelled as Assertion (A) and the other labelled as Reason (R). Assertion (A): ATP is used at two steps in glycolysis. Reason (R): The first ATP is used in converting glucose into glucose-6-phosphate and the second ATP is used in converting fructose-6-phosphate into fructose-1,6-bisphosphate. In the light of the above statements, choose the correct answer from the options given below. [NEET 2023]
  1. Both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.
  2. Both Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.
  3. Assertion is true but the Reason is false.
  4. Both Assertion and Reason are false.
Show answer
Answer: (A) Both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.
Explanation: Both statements are true and the Reason correctly explains the Assertion. In the preparatory (investment) phase of glycolysis, ATP is consumed twice: first when hexokinase phosphorylates glucose to glucose-6-phosphate, and second when phosphofructokinase phosphorylates fructose-6-phosphate to fructose-1,6-bisphosphate. The Reason precisely identifies these two steps.

Question 13

Previous-year question
The connecting link between glycolysis and the Krebs cycle is the conversion of pyruvate into [1990]
  1. lactate
  2. oxaloacetate
  3. acetyl CoA
  4. phosphoenolpyruvate
Show answer
Answer: (C) acetyl CoA
Explanation: Pyruvate entering the mitochondrial matrix is oxidatively decarboxylated by the pyruvate dehydrogenase complex, losing a carbon as carbon dioxide and reducing NAD⁺, and the remaining two-carbon fragment is linked to coenzyme A. The acetyl CoA so formed condenses with oxaloacetate to begin the Krebs cycle.

Question 14

Previous-year question
The enzyme hexokinase, which converts glucose to glucose-6-phosphate in glycolysis, is inhibited by glucose-6-phosphate. This is an example of [1996]
  1. feedback allosteric inhibition
  2. competitive inhibition
  3. positive feedback
  4. non-competitive inhibition
Show answer
Answer: (A) feedback allosteric inhibition
Explanation: The product of the reaction binds to a site on the enzyme other than the active site and reduces its activity, so the pathway slows when its own product accumulates. Because the inhibitor is the end product acting at an allosteric site, this is feedback allosteric inhibition.

Question 15

Previous-year question
In glycolysis, during oxidation, electrons are removed by [2006]
  1. NAD⁺
  2. ATP
  3. molecular oxygen
  4. glyceraldehyde-3-phosphate
Show answer
Answer: (A) NAD⁺
Explanation: The oxidative step of glycolysis is the conversion of glyceraldehyde-3-phosphate into 1,3-bisphosphoglycerate, in which two electrons and a proton are transferred to NAD⁺ to give NADH. Molecular oxygen takes no part in glycolysis, which is why the pathway proceeds equally in anaerobic conditions.

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