Respiration in Plants : 12th Class Biology Question Answer Lesson 12 – NIOS

Respiration in Plants : 12th Class Biology Question Answer Lesson 12 – NIOS

Respiration in Plants : 12th Class Biology Question Answer Lesson 12 - NIOS


  1. How do plant and other organisms obtain energy for various activites such asgrowth?
    Ans. The green Plants convert solar energy to chemical energy and store it inthe form of complex organic molecules. During respiration, they are oxidised and large amount of energy is released. This is stored as ATP. Plants use this ATP for metabolic activities.
  2. Name the energy-rich molecule formed during respiration from food.
    Ans. In the form of ATP.
  3. Give two differences between aerobic and anaerobic respiration.


  1. Name the surfaces that help plants in taking up oxygen from the atmosphere.
    Ans. Gaseous exchange takes place through the general body surface of the plants; through the stomata; and the lenticels.
  2. Name the process by which oxygen is taken up by the plants from the
    Ans. Diffusion
  3. Name the gases given out by plants during day time and night.
    Ans. Oxygen ; Carbon dioxide
  4. Why do plants not have any special respiratory organs like animals? Give two reasons.
    Ans. They have a large surface area to allow exchange of gases from and
    (b) their requirement of oxygen is much less.


  1. Why is pyruvic acid converted into alcohol or lactic acid during fermentation?
    Ans. In the presence of O2, it is completely broken down to simple forms such as CO2 and H2O.
    2Pyruvic acid + 6O2 ⎯→ 6CO2 + 6H2O + 30ATP (8ATP are obtained from glycolysis)

    In the absence of O2 they carry out alcoholic fermentation.
    2Pyruvic acid ⎯→ 2Ethyl alcohol + 2CO2
  2. Why is there less release of energy during anaerobic respiration?
    Ans. This is becausse organic molecules are only partially oxidised in anaerobic respiration and much of the energy remains in the end products such as alcohol or lactic acid.
  3. List the three phases of aerobic respiration of glucose. Where in the cell do these reactions take place?
    Ans. Glycolysis – in cytosol
    Krebs’ Cycle – matrix of mitochondria
    E.T.C. – inner membrane of mitochondria
  4. What is the role of O2 in aerobic respiration?
    Ans. O2 acts as the terminal acceptor of electrons and H2, removed from the glucose molecule and gets reduced to H2O.
  5. Name the substrate and products of Krebs’ Cycle.
    Ans. Substrate- Acetyl CoA
    Product-2 CO2, 3 NADH2, 1 FADH2, 1 ATP

  6. How do fatty acids enter Krebs’ Cycle?
    Ans. Fatty Acid undergoes β oxidation and produces acetyl CoA. This can enter the Kreb’s Cycle
  7. When the amount of CO2 uptake during photosysthesis is equal to the amountof CO2 generated through respiration, it is called ……………
  8. What is amphibolic pathway?


  1. What is the R.Q. for carbohydrates and fats?
    Ans. R.Q. is 1
  2. What is the effect of high concentration of O Plants and animals 2 on respiration?
    Ans. Rate of respiration increases up to a point and beyond this point its rateof increase falls.
  3. What is the ideal temperature for the process of respiration ?
    Ans. 30-35°C
  4. Define R.Q.
    Ans. It is the ratio of the volume of CO2 evolved to the volume of O2 consumedin respiration. It gives us an idea of the kind of substrate used for respiration.
  5. What is the limiting factor of respiration in dry seeds?
    Ans. Water for hydration of respiratory enzymes.


  1. Name the products that are formed when RUBP combines with O2. Name the enzyme that is responsible for this reaction.
    Ans. Products are1 P.G.A. and 1 Phosphoglycolate
  2. Give one point of difference between respiration and photorespiration.?
  3. State the conditions under which photorespiration occurs?
    Ans. (a)Light
    (b) High concentration of O2
    (c) Low concentration of CO2


  1. Define respiration
  2. What is the role of O2 in electron transport chain (ETC)?
  3. How many molecules of ATP are released when a molecule of glucose is oxidised to
    (a) CO2 and H2O?
    (b) Ethyl alcohol and CO2?
  4. Write the equation for aerobic respiration.
  5. Name the end products of electron transport chains.
  6. Respiration is a continuous process in green plants. Then why is it that they give out O2 and not CO2 during the day?
  7. What is the site for
    (a) Glycolysis,
    (b) Krebs Cycle,
    (c) ATP generation by oxidative phosphorylation?
  8. What is the fate of pyruvic acid in the (a) presence, and (b) absence of oxygen?Write the equations representing the processes, that take place in (a) & (b).
  9. What is the significance of stepwise oxidation of organic molecules instead ofone step reaction?
  10. What is the significance of photorespiration?
  11. List the substrates that enter and the products produced in
    (a) Glycolysis
    (b) Krebs Cycle
  12. How is yeast useful in industry? Give any three examples.
  13. How does exchange of respiratory gases take place in plants
  14. Define RQ. What is its significance?
  15. Mention the significance of TCA cycle.
  16. Why does fermentation yield less energy than aerobic respiration?
  17. List any 2 important contributions of PPP in a cell.
  18. What are the three major phases of glycolysis?
  19. What is the importance of Krebs’ Cycle?
  20. Differentiate between aerobic and anaerobic respiration
  21. Why is photorespiration a wasteful reaction?
  22. What is respiratory chain or ETC? What is its significance?
  23. Discuss the site of Pentose Phosphate Pathway in a cell.

NIOS 12th class biology Q Ans

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