NCERT Class 11 Science — Chapter 2: Respiration in Plants

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Assertion (A): The respiratory balance sheet calculation assumes that NADH produced in glycolysis is transferred to mitochondria. Reason (R): Glycolysis takes place within the mitochondrial matrix where the Krebs cycle occurs.

Official previous-year question

Verified 1 Aug 2026.

Options

ABoth A and R are true and R is the correct explanation of A
BBoth A and R are true but R is NOT the correct explanation of A
CA is true but R is false
DA is false but R is true

Did you get this right?

Solution

The correct option is

A is true but R is false

Explanation

The respiratory balance sheet is a theoretical calculation used to estimate the net gain of ATP from the complete oxidation of one glucose molecule. These calculations are based on specific assumptions regarding the sequential functioning of metabolic pathways and the transfer of intermediates between cellular compartments.

Statement-wise Analysis

Assertion (A): Correct
The calculation of the net ATP yield assumes a sequential, orderly pathway where NADH synthesized during glycolysis is transferred into the mitochondria. Since oxidative phosphorylation (the process that converts NADH to ATP) occurs on the inner mitochondrial membrane, the NADH produced in the cytoplasm during glycolysis must be transported into the mitochondria to contribute to the total ATP count.
Reason (R): Incorrect
Glycolysis occurs in the cytoplasm (cytosol) of the cell, not within the mitochondrial matrix. It is the Krebs cycle (Tricarboxylic Acid Cycle) that takes place within the mitochondrial matrix. Because glycolysis and the Krebs cycle occur in different compartments, the NADH produced in glycolysis requires specific shuttle systems (like the malate-aspartate shuttle or glycerol-3-phosphate shuttle) to enter the mitochondria.

Key Takeaway: Glycolysis is an anaerobic process occurring in the cytoplasm, whereas the Krebs cycle occurs in the mitochondrial matrix. The respiratory balance sheet assumes the successful transport of cytoplasmic NADH into the mitochondria for oxidative phosphorylation.

Your note

More from Chapter 2: Respiration in Plants

Assertion (A): Plants do not present great demands for gas exchange compared to animals. Reason (R): Each plant part takes care of its own gas-exchange needs, resulting in massive transport of gases from one part to another.

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Match the enzyme with its specific action: List I | List II A. Hexokinase | 1. Converts Pyruvate to Acetyl CoA B. Invertase | 2. Reduces Pyruvate to Lactic acid C. Lactate dehydrogenase | 3. Splits Sucrose into Glucose and Fructose D. Pyruvate dehydrogenase | 4. Phosphorylates Glucose Select the correct answer using the code given below

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Assertion (A): Oxygen plays a vital role in the early stages of the Krebs cycle. Reason (R): Oxygen acts as the final hydrogen acceptor in the electron transport system.

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Match the respiratory substrate/enzyme with its entry or action: List I | List II A. Fatty acids | 1. Degrade proteins B. Glycerol | 2. Enter pathway as Acetyl CoA C. Amino acids | 3. Enter pathway as PGAL D. Proteases | 4. Enter at various stages after deamination Select the correct answer using the code given below

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Match the respiration context with its feature: List I | List II A. Yeast | 1. Site of Glycolysis B. Muscle cells (during heavy exercise) | 2. Site of Krebs’ cycle C. Mitochondria | 3. Produces Ethanol and CO₂ D. Cytoplasm | 4. Produces Lactic acid Select the correct answer using the code given below

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The correct option is

A is true but R is false

Explanation

Statement-wise Analysis

Assertion (A): Correct
The calculation of the net ATP yield assumes a sequential, orderly pathway where NADH synthesized during glycolysis is transferred into the mitochondria. Since oxidative phosphorylation (the process that converts NADH to ATP) occurs on the inner mitochondrial membrane, the NADH produced in the cytoplasm during glycolysis must be transported into the mitochondria to contribute to the total ATP count.
Reason (R): Incorrect
Glycolysis occurs in the cytoplasm (cytosol) of the cell, not within the mitochondrial matrix. It is the Krebs cycle (Tricarboxylic Acid Cycle) that takes place within the mitochondrial matrix. Because glycolysis and the Krebs cycle occur in different compartments, the NADH produced in glycolysis requires specific shuttle systems (like the malate-aspartate shuttle or glycerol-3-phosphate shuttle) to enter the mitochondria.