Respiration in Plants — Class 11 Biology NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 11 Biology chapter "Respiration in Plants" — 8 important questions with detailed answers for CBSE board exam preparation.

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TL;DR: Free step-by-step NCERT solutions for Class 11 Biology chapter "Respiration in Plants" — 8 important questions with detailed answers for CBSE board ex…

Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated Jul 23, 2026

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Key Questions Covered:

Define respiration. Why is it essential for plants?
What are the stages of aerobic respiration?
Describe glycolysis. Where does it occur and what are its products?
What is anaerobic respiration? Give examples in plants.
Distinguish between aerobic and anaerobic respiration.
What is the Krebs cycle? List its main products.
+ 2 more questions in the full chapter

Solutions Summary:

Question	Status
Define respiration. Why is it essential for plants?	✓ Solved
What are the stages of aerobic respiration?	✓ Solved
Describe glycolysis. Where does it occur and what are its…	✓ Solved
What is anaerobic respiration? Give examples in plants.	✓ Solved
Distinguish between aerobic and anaerobic respiration.	✓ Solved
What is the Krebs cycle? List its main products.	✓ Solved

Showing 6 of 8 questions

Q1: Define respiration. Why is it essential for plants?

Respiration is a catabolic process in which organic compounds are oxidized to release energy in the form of ATP. In plants, it occurs continuously in all living cells. Essential for: - Providing ATP (energy currency) for all life processes - Biosynthetic reactions (protein, nucleic acid synthesis) - Active transport and ion uptake - Maintenance of cell structure and turgor - Growth and reproduction Unlike photosynthesis, respiration occurs 24 hours in all parts of the plant.

Q2: What are the stages of aerobic respiration?

Aerobic respiration has three stages: 1. Glycolysis (cytoplasm): Glucose (6C) → 2 Pyruvate (3C) + 2 ATP + 2 NADH 2. Krebs cycle/Citric Acid Cycle (mitochondrial matrix): Acetyl-CoA completely oxidized, releases CO2 + 8 NADH + 2 FADH2 + 2 ATP 3. Electron Transport Chain (inner mitochondrial membrane): NADH and FADH2 oxidized, O2 reduced to H2O, ~32-34 ATP generated Total yield: ~36-38 ATP per glucose molecule

Q3: Describe glycolysis. Where does it occur and what are its products?

Glycolysis is the breakdown of one molecule of glucose (6C) into two molecules of pyruvate (3C). Location: Cytoplasm Main steps: - Glucose → Glucose-6-phosphate → Fructose-1,6-bisphosphate (uses 2 ATP) - Fructose-1,6-bisphosphate → 2 G3P (3-carbon molecules) - G3P → Pyruvate (produces 4 ATP + 2 NADH) Net products: 2 Pyruvate + 2 ATP (net) + 2 NADH Glycolysis is anaerobic and does not require oxygen.

Q4: What is anaerobic respiration? Give examples in plants.

Anaerobic respiration is oxidation of organic compounds without oxygen. Two main types in plants: 1. Alcoholic fermentation: Pyruvate → Ethanol + CO2 (occurs in yeast, many plant roots) 2. Lactic acid fermentation: Pyruvate → Lactic acid (occurs in muscle cells and some plants) Both regenerate NAD+ from NADH so glycolysis continues. Yields only 2 ATP per glucose (much less than aerobic). Occurs when oxygen is limited, e.g., in waterlogged soils, during flooding, in germinating seeds without suff...

Q5: Distinguish between aerobic and anaerobic respiration.

Aerobic respiration: Requires O2 as final electron acceptor. Complete oxidation of glucose. Occurs in cytoplasm and mitochondria. Produces ~36-38 ATP per glucose. End products: CO2 and H2O. Anaerobic respiration: No O2 required. Incomplete oxidation. Occurs in cytoplasm only. Produces only 2 ATP per glucose. End products: Ethanol/Lactic acid and CO2 (in fermentation). Aerobic is much more efficient and is the primary mode in most plant cells under normal conditions.

Q6: What is the Krebs cycle? List its main products.

The Krebs cycle (Citric Acid Cycle/TCA cycle) is a series of enzyme-catalyzed reactions occurring in the mitochondrial matrix. Acetyl-CoA (2C) combines with oxaloacetate (4C) to form citrate (6C), which is progressively oxidized back to oxaloacetate. Main products per turn (1 Acetyl-CoA): - 3 NADH (used in electron transport chain) - 1 FADH2 (used in electron transport chain) - 1 GTP/ATP (direct energy) - 2 CO2 (complete oxidation of acetyl group) The cycle occurs twice per glucose (2 Acetyl-CoA...

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