Introduction to Respiration in Plants
Respiration in plants mcq is a fundamental biological process that involves the breakdown of organic molecules to release energy. Unlike animals, plants do not have specialized respiratory systems. Instead, they rely on diffusion to exchange gases through stomata, lenticels, and root hairs.
While photosynthesis is responsible for producing glucose, respiration ensures the energy stored in glucose is converted into ATP (adenosine triphosphate), which is crucial for metabolic functions. NEET aspirants must have a deep understanding of respiration in plants mcq, as it is an important topic in the syllabus.
Types of Respiration in Plants
1. Aerobic Respiration
- This occurs in the presence of oxygen.
- It is the most efficient form of respiration, producing the highest ATP yield.
- The glucose molecule is completely oxidized into carbon dioxide and water.
Equation:C6H12O6+6O2→6CO2+6H2O+38ATPC_6H_{12}O_6 + 6O_2 → 6CO_2 + 6H_2O + 38ATPC6H12O6+6O2→6CO2+6H2O+38ATP
2. Anaerobic Respiration
- This occurs in the absence of oxygen.
- It is less efficient as glucose is only partially broken down.
- Produces alcohol or lactic acid as byproducts.
Equation (Alcoholic fermentation in yeast):C6H12O6→2C2H5OH+2CO2+2ATPC_6H_{12}O_6 → 2C_2H_5OH + 2CO_2 + 2ATPC6H12O6→2C2H5OH+2CO2+2ATP
Mechanism of Respiration
Respiration in plants occurs in three major steps:
1. Glycolysis (Cytoplasm)
- The first step of respiration is where glucose (C₆) is broken into two molecules of pyruvate (C₃).
- Produces a net gain of 2 ATP and 2 NADH.
2. Krebs Cycle (Mitochondria)
- Pyruvate is converted into acetyl-CoA, which enters the Krebs cycle.
- Produces NADH, FADH₂, and GTP (energy equivalents).
3. Electron Transport Chain (Mitochondria)
- Uses NADH and FADH₂ to generate ATP through oxidative phosphorylation.
- Produces 34 ATP molecules.
Factors Affecting Respiration in Plants
- Temperature: Higher temperatures increase enzyme activity, but excessive heat can denature them.
- Oxygen Availability: Essential for aerobic respiration; a lack of oxygen leads to anaerobic respiration.
- Water Content: Water deficiency slows down respiration due to enzyme inactivation.
- Substrate Type: Different substrates yield different amounts of ATP (e.g., fats produce more ATP than carbohydrates).
Respiratory Quotient (RQ) and Its Importance
- Definition: The ratio of CO₂ evolved to O₂ consumed.
- Equation: RQ=CO2 evolvedO2 consumedRQ = \frac{\text{CO}_2 \text{ evolved}}{\text{O}_2 \text{ consumed}}RQ=O2 consumedCO2 evolved
- Values:
- Carbohydrates: RQ = 1
- Fats: RQ < 1
- Proteins: RQ ≈ 0.8
Multiple-choice questions (MCQs) on Plant Respiration
1. Which molecule acts as a common intermediate for the breakdown of carbohydrates, fats, and proteins?
A) Pyruvic acid
B) Acetyl CoA
C) Glucose
D) Fructose-1,6-bisphosphate
Answer: B) Acetyl CoA
Explanation: Acetyl CoA is the key intermediate that enters the Krebs cycle.
2. The end product of glycolysis is:
A) Citric acid
B) Pyruvic acid
C) Acetyl CoA
D) ATP
Answer: B) Pyruvic acid
Explanation: Glycolysis breaks glucose into two molecules of pyruvate.
3. In which organelle does the Krebs cycle occur?
A) Chloroplast
B) Mitochondria
C) Cytoplasm
D) Ribosome
Answer: B) Mitochondria
Explanation: The Krebs cycle (also called the citric acid cycle) takes place in the mitochondrial matrix, where pyruvate is further broken down to generate energy.
4. What is the main function of NADH and FADH₂ in respiration?
A) Act as enzymes
B) Transport electrons to the Electron Transport Chain (ETC)
C) Synthesize proteins
D) Convert glucose into pyruvate
Answer: B) Transport electrons to the Electron Transport Chain (ETC)
Explanation: NADH and FADH₂ are electron carriers that play a crucial role in oxidative phosphorylation by donating electrons to the ETC for ATP production.
5. What is the site of glycolysis?
A) Cytoplasm
B) Mitochondria
C) Nucleus
D) Chloroplast
Answer: A) Cytoplasm
Explanation: Glycolysis is the first step in respiration and occurs in the cytoplasm, where glucose is broken down into pyruvate.
6. What is the total number of ATP molecules produced in aerobic respiration from one glucose molecule?
A) 2
B) 38
C) 4
D) 12
Answer: B) 38
Explanation: In aerobic respiration, complete oxidation of one glucose molecule produces a net yield of 38 ATP molecules.
7. What is the final electron acceptor in aerobic respiration?
A) Carbon dioxide
B) Oxygen
C) NADH
D) Water
Answer: B) Oxygen
Explanation: Oxygen acts as the final electron acceptor in the Electron Transport Chain (ETC), forming water at the end of the process.
8. Which enzyme is responsible for ATP synthesis in mitochondria?
A) Rubisco
B) ATP synthase
C) PEP carboxylase
D) Amylase
Answer: B) ATP synthase
Explanation: ATP synthase is an enzyme that facilitates the synthesis of ATP from ADP and inorganic phosphate during oxidative phosphorylation.
9. In anaerobic respiration, what is the end product in muscle cells?
A) Ethanol
B) Lactic acid
C) Acetyl CoA
D) Carbon dioxide
Answer: B) Lactic acid
Explanation: Without oxygen, muscle cells perform lactic acid fermentation, converting pyruvate into lactic acid.
10. The RQ (Respiratory Quotient) value for the complete oxidation of glucose is:
A) 0.7
B) 1.0
C) 0.9
D) 1.2
Answer: B) 1.0
Explanation: The Respiratory Quotient (RQ) for carbohydrate oxidation (glucose) is 1.0, as the volume of CO₂ evolved is equal to the volume of O₂ consumed.
11. Which of the following processes occurs in both aerobic and anaerobic respiration?
A) Electron Transport Chain
B) Glycolysis
C) Krebs Cycle
D) Oxidative Phosphorylation
Answer: B) Glycolysis
Explanation: Glycolysis is the common pathway for both aerobic and anaerobic respiration, as it breaks glucose down into pyruvate.
12. Which intermediate compound links glycolysis to the Krebs cycle?
A) NADH
B) FADH₂
C) Acetyl CoA
D) Oxaloacetate
Answer: C) Acetyl CoA
Explanation: Pyruvate from glycolysis is converted into Acetyl CoA, which then enters the Krebs cycle.
13. Which gas is released during anaerobic respiration in yeast?
A) Oxygen
B) Carbon dioxide
C) Nitrogen
D) Hydrogen
Answer: B) Carbon dioxide
Explanation: In anaerobic respiration (fermentation), yeast converts glucose into ethanol and carbon dioxide.
14. What is the role of oxygen in respiration?
A) Provides energy
B) Acts as the final electron acceptor in the Electron Transport Chain
C) Converts glucose into ATP
D) Removes carbon dioxide
Answer: B) Acts as the final electron acceptor in the Electron Transport Chain
Explanation: Oxygen is required in the last step of aerobic respiration, where it accepts electrons and forms water.
15. What happens to pyruvate in anaerobic respiration?
A) It enters the Krebs cycle
B) It gets converted into ethanol or lactic acid
C) It is used for photosynthesis
D) It forms ATP directly
Answer: B) It gets converted into ethanol or lactic acid
Explanation: Pyruvate undergoes fermentation in anaerobic conditions, leading to the formation of ethanol (in yeast) or lactic acid (in muscles).
16. In which stage of respiration is the most ATP produced?
A) Glycolysis
B) Krebs Cycle
C) Electron Transport Chain
D) Fermentation
Answer: C) Electron Transport Chain
Explanation: The Electron Transport Chain produces the highest amount of ATP through oxidative phosphorylation.
17. The main site of ATP synthesis in aerobic respiration is:
A) Cytoplasm
B) Mitochondria
C) Chloroplast
D) Ribosome
Answer: B) Mitochondria
Explanation: ATP is primarily synthesized in the mitochondria during oxidative phosphorylation.
18. Which step in respiration does NOT produce ATP directly?
A) Glycolysis
B) Krebs Cycle
C) Electron Transport Chain
D) Pyruvate to Acetyl CoA conversion
Answer: D) Pyruvate to Acetyl CoA conversion
Explanation: The conversion of pyruvate to Acetyl CoA does not directly generate ATP but produces NADH, which later contributes to ATP synthesis.
19. What is the function of Coenzyme Q in the Electron Transport Chain?
A) Accepts oxygen
B) Transfers electrons between Complexes I and III
C) Synthesizes ATP
D) Converts NADH into FADH₂
Answer: B) Transfers electrons between Complexes I and III
Explanation: Coenzyme Q (Ubiquinone) plays a key role in shuttling electrons within the Electron Transport Chain.
20. Which enzyme catalyzes the first step of glycolysis?
A) ATP synthase
B) Hexokinase
C) Pyruvate kinase
D) Dehydrogenase
Answer: B) Hexokinase
Explanation: Hexokinase catalyzes the phosphorylation of glucose to glucose-6-phosphate in the first step of glycolysis.
Significance of MCQs in NEET Preparation
MCQs help students:
- Identify weak areas.
- Improve time management skills.
- Learn application-based concepts.
Tips and Tricks for Answering MCQs Correctly
- Read the question carefully.
- Eliminate incorrect options first.
- Manage your time effectively.
Conclusion
Respiration in plants is a crucial concept in the NEET syllabus. Regular practice of MCQs will enhance conceptual clarity and boost confidence. Study consistently and practice previous years’ NEET questions to score well.
For comprehensive coaching, visit NEET World.
FAQs on Respiration in Plants for NEET
1. Why do plants need respiration if they produce energy via photosynthesis?
Photosynthesis occurs only in light, while respiration is continuous, providing energy at all times.
2. What is the main site of respiration in plants?
Mitochondria are the primary site for ATP production in aerobic respiration.
3. What is the significance of the Electron Transport Chain?
It is the step where maximum ATP is generated.
4. How does respiration affect plant growth?
It provides the energy required for cell division and development.
5. What is the net ATP gain in anaerobic respiration?
Only 2 ATP per glucose molecule.
