Last Updated on September 27, 2025 by XAM CONTENT
To succeed in Class 11 Biology exams, a strong grasp of Chapter 12 – Respiration in Plants is essential. Our comprehensive collection of chapterwise MCQ questions with answers for Class 11 Biology is designed according to the latest syllabus and exam guidelines, ensuring targeted preparation and better performance. It is a part of MCQ Questions for CBSE Class 11 Biology Series.
These multiple-choice questions will help you assess your knowledge, improve accuracy, and boost confidence for your exams. Whether you are preparing for school tests, online tests or competitive exams, these Respiration in Plants MCQs will strengthen your conceptual clarity.
| Chapter | Respiration in Plants |
| Book | Biology for Class 11 |
| Type of Questions | MCQ Questions |
| Nature of Questions | Competency Based Questions |
| Board | CBSE |
| Class | 11 |
| Subject | Biology |
| Useful for | Class 11 Studying Students |
| Answers provided | Yes |
| Difficulty level | Mentioned |
| Important Link | Class 11 Biology Chapterwise MCQ Questions |
MCQ Questions on Respiration in Plants Class 11 Biology (PDF Download)
Question 1.
Which is the common step in both aerobic and anaerobic respiration?
(a) Glycolysis
(b) Krebs cycle
(c) ETS
(d) Oxidative phosphorylation
Show Answer
Answer: (a) Glycolysis
Explanation: Glycolysis occurs in the cytoplasm and is the first step of respiration in both aerobic and anaerobic pathways, breaking down glucose into pyruvate.
Question 2.
Where does glycolysis take place in a cell?
(a) Mitochondrial matrix
(b) Cytoplasm
(c) Inner mitochondrial membrane
(d) Chloroplast
Show Answer
Answer: (b) Cytoplasm
Explanation: Glycolysis is a cytoplasmic process that breaks one glucose molecule into two pyruvate molecules, producing ATP and NADH.
Question 3.
The net gain of ATP from one molecule of glucose in glycolysis is:
(a) 2 ATP
(b) 4 ATP
(c) 6 ATP
(d) 8 ATP
Show Answer
Answer: (a) 2 ATP
Explanation: Glycolysis produces 4 ATP molecules, but 2 are consumed in initial steps, giving a net gain of 2 ATP per glucose molecule.
Question 4.
Which of the following is the link between glycolysis and Krebs cycle?
(a) Oxaloacetate
(b) Acetyl‑CoA
(c) Pyruvate dehydrogenase
(d) Citrate
Show Answer
Answer: (b) Acetyl‑CoA
Explanation: Pyruvate from glycolysis is oxidatively decarboxylated to form Acetyl‑CoA, which then enters the Krebs cycle in the mitochondrial matrix.
Question 5.
The first stable compound of Krebs cycle is:
(a) Malate
(b) Citrate
(c) Oxaloacetate
(d) Fumarate
Show Answer
Answer: (b) Citrate
Explanation: Acetyl‑CoA condenses with oxaloacetate to form citrate, the first stable compound of the Krebs cycle.
Question 6.
How many molecules of NADH are formed from one turn of Krebs cycle?
(a) 2
(b) 3
(c) 4
(d) 6
Show Answer
Answer: (b) 3
Explanation: Each turn of the Krebs cycle produces 3 NADH, 1 FADH₂, and 1 GTP (ATP equivalent) per acetyl‑CoA.
Question 7.
Where does the electron transport system (ETS) operate in mitochondria?
(a) Outer membrane
(b) Inner membrane
(c) Matrix
(d) Intermembrane space
Show Answer
Answer: (b) Inner membrane
Explanation: ETS is located on the inner mitochondrial membrane, where electrons are passed along carriers, generating a proton gradient.
Question 8.
The terminal electron acceptor in aerobic respiration is:
(a) NAD⁺
(b) FAD
(c) O₂
(d) CO₂
Show Answer
Answer: (c) O₂
Explanation: Oxygen acts as the final electron acceptor in aerobic respiration, combining with electrons and protons to form water.
Question 9.
How many ATP molecules are produced in aerobic respiration from one molecule of glucose?
(a) 36–38 ATP
(b) 20–22 ATP
(c) 12–14 ATP
(d) 2 ATP
Show Answer
Answer: (a) 36–38 ATP
Explanation: Complete oxidation of one glucose molecule in aerobic respiration yields about 36–38 ATP depending on efficiency and shuttle systems.
Question 10.
Which of the following occurs in anaerobic respiration but not in aerobic respiration?
(a) Glycolysis
(b) Formation of lactic acid or ethanol
(c) Electron transport system
(d) Krebs cycle
Show Answer
Answer: (b) Formation of lactic acid or ethanol
Explanation: Anaerobic respiration involves incomplete breakdown of pyruvate into lactic acid (animals) or ethanol + CO₂ (plants, microbes).
Question 11.
Which enzyme catalyzes the conversion of pyruvate to ethanol during fermentation?
(a) Pyruvate dehydrogenase
(b) Alcohol dehydrogenase
(c) Lactate dehydrogenase
(d) PEP carboxylase
Show Answer
Answer: (b) Alcohol dehydrogenase
Explanation: Alcohol dehydrogenase converts acetaldehyde (from pyruvate) to ethanol in yeast and other organisms during fermentation.
Question 12.
Respiratory quotient (RQ) of carbohydrates is:
(a) 0.7
(b) 0.9
(c) 1.0
(d) 1.2
Show Answer
Answer: (c) 1.0
Explanation: RQ is the ratio of CO₂ evolved to O₂ consumed. For carbohydrates, complete oxidation gives an RQ of 1.0.
Question 13.
Which of the following respiratory substrates has the lowest RQ?
(a) Carbohydrates
(b) Fats
(c) Organic acids
(d) Proteins
Show Answer
Answer: (b) Fats
Explanation: Fats have an RQ of less than 1 (≈0.7) since more oxygen is required for their oxidation compared to CO₂ released.
Question 14.
Which step of respiration produces the highest number of ATP molecules?
(a) Glycolysis
(b) Krebs cycle
(c) ETS (Oxidative phosphorylation)
(d) Fermentation
Show Answer
Answer: (c) ETS (Oxidative phosphorylation)
Explanation: The electron transport system produces the bulk of ATP (about 32–34 molecules) via oxidative phosphorylation.
Question 15.
The enzyme ATP synthase is located in:
(a) Outer mitochondrial membrane
(b) Inner mitochondrial membrane
(c) Cytoplasm
(d) Ribosomes
Show Answer
Answer: (b) Inner mitochondrial membrane
Explanation: ATP synthase (F₀F₁ particle) is embedded in the inner mitochondrial membrane, using proton gradients to synthesize ATP.
Question 16.
In which part of the mitochondria are protons accumulated during electron transport?
(a) Matrix
(b) Intermembrane space
(c) Outer membrane
(d) Cristae
Show Answer
Answer: (b) Intermembrane space
Explanation: Proton pumps of ETS actively transport H⁺ into the intermembrane space, creating a proton gradient essential for chemiosmosis.
Question 17.
Pasteur effect is observed in:
(a) Increase in glycolysis under anaerobic conditions
(b) Decrease in glycolysis in presence of oxygen
(c) Inhibition of Krebs cycle
(d) Overproduction of ATP
Show Answer
Answer: (b) Decrease in glycolysis in presence of oxygen
Explanation: Pasteur effect refers to the suppression of fermentation when oxygen is available, as aerobic respiration is more efficient in ATP yield.
Question 18.
In anaerobic respiration of yeast, the end products are:
(a) Lactic acid only
(b) Ethanol and CO₂
(c) Pyruvate and ATP
(d) Glucose and water
Show Answer
Answer: (b) Ethanol and CO₂
Explanation: Yeast ferments pyruvate into ethanol and CO₂, regenerating NAD⁺ to sustain glycolysis.
Question 19.
RQ greater than 1 is observed when the respiratory substrate is:
(a) Carbohydrate
(b) Fat
(c) Organic acid
(d) Protein
Show Answer
Answer: (c) Organic acid
Explanation: Oxidation of organic acids releases more CO₂ compared to oxygen consumed, giving an RQ value greater than 1.
Question 20.
The process of oxidative phosphorylation is directly linked with:
(a) Glycolysis
(b) Substrate‑level phosphorylation
(c) Electron transport chain
(d) Fermentation
Show Answer
Answer: (c) Electron transport chain
Explanation: Oxidative phosphorylation occurs in mitochondria, where energy from electron transport is used to pump protons, and ATP synthase converts ADP to ATP.
We hope the given mcq questions with Answers for Respiration in Plants Class 11 helps you in your learning.
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Topics from which mcq questions may be asked
- Glycolysis
- Kreb’s cycle
- Fermentation
Respiration provides the energy needed for every living process.
Frequently Asked Questions (FAQs) on Respiration in Plants MCQ Questions
Q1: What is the best way to prepare for Class 11 Biology MCQ questions?
A1: The best way is to study NCERT concepts thoroughly, practice topicwise MCQs regularly. Solving previous year MCQs and mock tests can boost accuracy and speed.
Q2: Are NCERT questions enough for Class 11 Biology MCQ-based exams?
A2: NCERT forms the base for all CBSE Physics MCQs. However, for better preparation, students should solve additional MCQs from reference books and practice HOTS and competency-based questions to develop better understanding.
Q3: Where can I find chapterwise Class 11 Biology MCQ questions with answers?
A3: You can find chapterwise MCQ questions with answers and detailed explanations on trusted educational platforms like xamcontent.com and physicsgurukul.com. These cover both basic and advanced-level questions.
Q4: Do CBSE Class 11 exams include MCQs?
A4: Yes, as per the latest CBSE exam pattern, objective questions, including MCQs, are part of the final exam paper. MCQs test conceptual understanding and application skills.
Q5: How to score high in Class 11 Biology MCQs?
A5: To score high, understand the theory from NCERT, solve a variety of MCQs (basic and conceptual), and regularly revise theory. Avoid guesswork and focus on time management during tests.
