Respiration In Plants Question And Answers

Class 11 Biology WBCHSE Respiration In Plants Some Important Questions And Answers

Question 1. Name the main three events that occur during glycolysis.
Answer:

The main three events of glycolysis are—

1. Oxidation of glucose and synthesis of pyruvate.
2. Reduction of NAD and formation of NADH+H⁺
3. Formation of ATP from ADP by substrate-level phosphorylation.

Question 2. Respiration is known as an exothermic process. Why?
Answer: During respiration respiratory substrates are oxidized to convert static energy into kinetic energy. Some percentage of this energy is stored in highly energized ATP compounds as chemical energy. The rest of the kinetic energy is converted into heat energy. Because of this release of heat energy and so, respiration is known as an exothermic process.

Question 3. Why is glucose considered as the ‘starting point of respiration’?
Answer: The substances, oxidised in the cytoplasm during respiration are known as respiratory substrates. Among all the substances, glucose is used as the primary respiratory substrate. Hence, glucose is considered the ‘starting point of respiration’.

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Question 4. What is the pentose phosphate pathway?
Answer: The pentose phosphate pathway is an alternative pathway of glycolysis or EMP pathway. NADPH+H⁺ is produced by this pathway. This pathway also takes part in the synthesis of fats and nucleic acids.

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Question 5. What happens to the reactions of the TCA cycle in the absence of oxygen?
Answer: In the electron transport chain, NADH+H⁺ and FADH₂ are oxidized in the presence of oxygen to form NAD and FAD respectively. The FAD and NAD are again used in the TCA cycle in the presence of oxygen. These two compounds keep the TCA cycle running. So, reactions of the TCA cycle stop in the absence of oxygen.

Question 6. What is the fate of products, produced during glycolysis?
Answer: Pyruvic acid is produced during glycolysis. Pyruvic acid follows any of the following three processes to produce more energy.

The processes are—

1. lactic acid fermentation,
2. Ethyl alcohol fermentation,
3. Krebs cycle. The fate of pyruvic acid depends on the availability of free oxygen.

Question 7. Name the enzymes present in the mitochondrial matrix.
Answer:

The following enzymes are present in the mitochondrial matrix—

1. Citric acid synthetase
2. Isocitrate dehydrogenase
3. A-ketoglutarate dehydrogenase
4. Fumarate
5. Malate dehydrogenase.

Question 8. Name the enzymes present in the inner mitochondrial membrane, which take part in cellular respiration.
Answer:

The enzymes present in the inner mitochondrial membrane that take part in cellular respiration are—

1. Cytochrome C reductase,
2. NADH dehydrogenase,
3. Succinate dehydrogenase,
4. Glycerol 3-phosphate dehydrogenase and
5. ATP synthase.

Question 9. Name the inhibitors of the Krebs cycle.
Answer:

Some compounds that act as inhibitors of the Krebs cycle are—

1. Fluoroacetate which inhibits the action of aconitase enzyme;
2. Arsenite which inhibits dehydrogenase;
3. Malonate inhibits the action of succinate dehydrogenase.

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Question 10. Why is aerobic respiration more important than anaerobic respiration?
Answer: 686 kcal energy is released by oxidation of 1 molecule of glucose during aerobic respiration whereas, only 28-40 kcal energy is released during anaerobic respiration. Again, during aerobic respiration, CO₂ and water are released as byproducts.

But during anaerobic respiration, ethyl alcohol is produced in plants, and lactic acid is produced in animals, as a byproduct. These products are harmful to the respective organisms. Hence, aerobic respiration is more important than anaerobic respiration.

Question 11. How does gaseous exchange occur in plants, though they do not have any special respiratory organs?
Answer: In plants, gaseous exchange occurs throughout the body surface. The amount of gaseous exchange is low in plants as compared to animals. Gaseous exchange also occurs in plants through some special openings like stomata and lenticels. The gaseous exchange takes place in different parts of the plants by diffusion, through intercellular space present between the matured parenchyma cells.

Question 12. Why is carbon dioxide not produced during glycolysis?
Answer: Carbon dioxide is not produced during glycolysis because decarboxylation of carbohydrates does not occur in the process of glycolysis.

Question 13. What is oxidative decarboxylation?
Answer: The process where pyruvic acid is transported to the mitochondrial matrix from the inner mitochondrial membrane by a specific transport protein and is oxidized to produce carbon dioxide is known as oxidative decarboxylation.

Question 14. What is the Crabtree effect?
Answer: The oxygen consumption is suppressed by a high concentration of glucose in the living cells. This phenomenon is known as the Crabtree effect.

Class 11 Biology WBCHSE Respiration In Plants VeryShort Answer Type Questions

Question 1. Name the site of oxidative phosphorylation.
Answer: Oxysomes are the sites of oxidative phosphorylation.

Question 2. Why is fructose 6-phosphate known as fructose monophosphate?
Answer: As it contains a single phosphate group at carbon 6, it is known as fructose monophosphate.

Question 3. What is the alternate name for fructose bisphosphate?
Answer: Fructose 1,6-bisphosphate or fructose 2,6-bisphosphate.

Question 4. How many highly energized phosphates are present in 1 molecule of ATP?
Answer: There are 2 highly energized phosphates in ATP— phosphate and y phosphate.

Question 5. Write down the elementary difference between 3-phosphoglycerate and 2-phosphoglycerate.
Answer: In 3-PGA, the phosphate group remains at carbon number 3, while in 2-PGA the same is enzymatically shifted to carbon 2 of the molecule.

Question 6. What is the unit of oxidative photophosphorylation?
Answer: The unit of oxidative phosphorylation is kJ/mol.

Question 7. How many ATP molecules are synthesized during the glycolysis phase of anaerobic respiration?
Answer: 2 ATP molecules are formed in anaerobic glycolysis.

Question 8. What is the site for terminal respiration?
Answer: In prokaryotes, it occurs in the cell membrane, and in eukaryotes, it occurs in the cristae of the inner mitochondrial membrane

Question 9. Name the special structures present on leaves that are responsible for gaseous exchange in plants.
Answer: Stomata are special structures present in the leaf epidermis and are responsible for gaseous exchange

Question 10. AnsweGive the location of enzymes involved in the Krebs cycle.
Answer: All the enzymes participate actively in the Krebs cycle, except succinate dehydrogenase, which remains dissolved in the mitochondrial matrix. It is one of the components of Complex II of ETS present on the inner mitochondrial membrane

Question 11. Mention the location of coenzymes of ETS in mitochondria.
Answer: The coenzymes remain dissolved in the mitochondrial matrix.

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Question 12. What is the other name for TCA Cycle?
Answer: The other name of TCA cycle is the Citric Acid Cycle or Krebs cycle.

Question 13. What is the full form of ETS? Where does it occur?
Answer: ETS stands for electron transport system. It occurs in the inner mitochondrial membrane.

Question 14. What are respiratory substrates?
Answer: The organic substances that are catabolized or broken down enzymatically in cellular respiration to release energy are known as respiratory substrates.

Question 15. How many highly energized phosphate compounds (ATP) can be obtained from one molecule of glucose?
Answer: 38 highly energized phosphate compounds (ATP) are obtained from 1 molecule of glucose.

Question 16. What are the raw materials for cellular respiration?
Answer: The energy fuels for cellular respiration are carbohydrates (usually glucose). Lipids and proteins may also be used as substrates for respiration under certain conditions.

Question 17. What is the function of ATP?
Answer: It provides energy for the cellular activities. So, it is often referred to as energy currency.

Question 18. How many molecules of ATP are net gained in Krebs cycle and glycolysis?
Answer: 12 ATP in the Krebs cycle and 2 ATP in glycolysis.

Question 19. What is zymosis?
Answer: The process of anaerobic respiration in yeast is known as zymosis.

Question 20. Which phase connects glycolysis and the TCA cycle?
Answer: The oxidative decarboxylation of pyruvate to acetyl CoA in the mitochondrial matrix is the connecting step of glycolysis and the TCA cycle.

Question 21. Name the stage of respiration that releases 1 molecule of H₂O as one of the respiratory products.
Answer: During terminal respiration, one molecule of H₂O is one of the respiratory products.

Question 22. Which compound acts as energy currency in plants and animals?
Answer: ATP functions as an energy currency in plants and animals.

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Question 23. What is synthesized by the F₀-F₁ complex?
Answer: They constitute the ATP synthase enzyme and synthesize ATP if a proton gradient is available across the mitochondrial membrane.

Question 24. Name the main compound produced during glycolysis in skeletal muscles and fermentation in yeast.
Answer: Lactate (lactic acid) is formed in skeletal muscle during glycolysis and ethanol (ethyl alcohol) is formed during fermentation in yeast.

Question 25. How many grams of glucose is oxidized during aerobic respiration?
Answer: 180 gm of glucose are oxidized during aerobic respiration.

Question 26. What is RQ?
Answer: RQ or respiratory quotient is the ratio of the volume of carbon dioxide liberated in respiration with the volume of oxygen consumed by a respiring tissue (or organism) for the same time period.

Question 27. Which type of respiration has an infinite RQ value?
Answer: In the fermentation process, the RQ value of glucose is infinity (oo) .

Question 28. Mention the significance of RQ.
Answer: The chemical nature of the respiratory substrate can be determined by knowing the RQ value.

Question 29. What is terminal oxidation?
Answer: Terminal oxidation is the final step in aerobic respiration which involves the oxidation of protons (H+) released by the coenzymes during oxidative phosphorylation, by the final acceptor of protons, i.e., oxygen, which also accepts electrons coming from ETS 4H⁺ + O₂ + 4e^– —> 2H₂O

Question 30. Name one compound produced during the anabolic phase of the Krebs cycle.
Answer: Cis-aconitate.

Question 31. Who observed the similarities between respiration and combustion?
Answer: Lavoisier observed the similarities between respiration and combustion

Question 32. Which plant shows zero RQ value?
Answer: During the night, the respiratory CO₂ is utilized to synthesize organic acid by CAM plants (such as Bryophyllum). O₂ consumption, therefore, takes place without concomitant CO₂ evolution and the RQ value becomes zero.

Question 33. Name the first complex of the electron transport chain or ETC.
Answer: The name of the first complex of the electron transport chain is NADH dehydrogenase.

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Question 34. In which process does zymase act as an essential enzyme?
Answer: In the fermentation of sugar into ethanol and carbon dioxide, zymase acts as an essential enzyme.

Question 35. Name the two main compounds produced in heterotactic fermentation.
Answer: In heterotactic fermentation ethanol and lactic acid are produced.

Question 36. What type of substrates have an RQ of 1?
Answer: Carbohydrates are the respiratory substrate having an RQ of 1.

Question 37. Where does anaerobic respiration occur in the human body?
Answer: Anaerobic respiration occurs in skeletal muscle cells of the human body when they lack sufficient oxygen supply.

Question 38. Which phase of glycolysis directly produces water?
Answer: Dehydration of 2-phosphoglycerate to phosphoenolpyruvate catalyzed by enolase, directly produces water molecules.

Question 39. Mention the step of the citric acid cycle, which is not mediated by dehydrogenase enzyme.
Answer: Conversion of oxaloacetic acid to citric acid is not mediated by dehydrogenase enzyme.

Question 40. What is oxidative phosphorylation?
Answer: The process of ATP formation, as a result of the transportation of electrons from NADH or FADH₂ to O₂ through a series of electron carriers is known as oxidative phosphorylation.