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CNMS ICSE - 7 Std
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Chapter: 05. Respiration In Plants

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Test Yourself

A. Multiple Choice Questions

Energy is released during (a) Internal respiration (b) External respiration © Cell respiration (d) Breathing
Answer: © Cell respiration
Respiration is a (a) Physical process (b) Chemical process © Biochemical process (d) Physicochemical process
Answer: © Biochemical process
Which of the following statements is not correct about cellular respiration? (a) Energy is released (b) Occurs in all living forms © Oxygen is used and
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is liberated (d)
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is used to produce energy
Answer: (d)
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is used to produce energy
During respiration, yeast produces (a) Heat and energy (b) Ethyl alcohol and energy © Alcohol, carbon dioxide and energy (d) Water, carbon dioxide and energy
Answer: © Alcohol, carbon dioxide and energy
Exchange of respiratory gases in plants takes place through (a) Stomata (b) Entire leaf surface © Roots (d) Buds and flowers
Answer: (a) Stomata
Respiration is a (a) Catabolic process (b) Anabolic process © Catabolic endergonic reaction (d) Anabolic exergonic reaction
Answer: (a) Catabolic process
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B. Assertion-Reason Type Questions

Directions: Choose the correct option: ​(a) Both Assertion [A] and Reason [R] are true. ​(b) Both Assertion [A] and Reason [R] are false. ​© Assertion [A] is true but Reason [R] is false. ​(d) Assertion [A] is false but Reason [R] is true.
Assertion [A]: In anaerobic respiration, one of the end products is alcohol. ​Reason [R]: There is an incomplete breakdown of glucose.
Answer: (a) Both Assertion [A] and Reason [R] are true.
Assertion [A]: The opening and closing of stomatal pore is a function of the guard cells. ​Reason [R]: Stomatal pores are the site of aerobic respiration.
Answer: © Assertion [A] is true but Reason [R] is false. (Note: Stomatal pores are the sites of gaseous exchange/breathing, whereas aerobic respiration occurs inside the mitochondria of cells.)
Assertion [A]: Plants have complex respiratory organs. ​Reason [R]: Each part of a plant can independently take in oxygen from surrounding air and give out
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.
Answer: (d) Assertion [A] is false but Reason [R] is true. (Note: Plants do not have specialized respiratory organs.)
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C. Fill in the blanks with suitable words.

Leaves have ________ for gaseous exchanges.
Answer: stomata
________ respiration occurs in yeast cells.
Answer: Anaerobic
Waste product of respiratory process is ________.
Answer: carbon dioxide
Exchange of respiratory gases is between ________ and ________.
Answer: atmosphere (or air), cells
________ is taken in and ________ is expelled during gaseous exchange.
Answer: Oxygen, carbon dioxide
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D. State whether these statements are true or false. If false, rewrite the correct form of statements.

Most plants depend on anaerobic respiration.
Answer: False. Most plants depend on aerobic respiration.
Cell respiration is an exergonic process.
Answer: True.
Plants carry out photosynthesis only during daytime and respiration only at night.
Answer: False. Plants carry out photosynthesis only during daytime and respiration all the time (both day and night).
No carbon dioxide is released by plant cells during daytime.
Answer: False. Carbon dioxide is released by plant cells during respiration in the daytime, but it is immediately reused for photosynthesis instead of being released into the environment.
Root cells obtain oxygen from air.
Answer: True.
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E. Give one word for the following.

Anaerobic breakdown of sugars into alcohol.
Answer: Fermentation
The biochemical process during which glucose is oxidised into carbon dioxide and water.
Answer: Aerobic respiration (or Cellular respiration)
The energy rich compound in a cell.
Answer: ATP (Adenosine Triphosphate)
Cell organelle in which aerobic respiration is completed.
Answer: Mitochondria
Spaces in old stems below bark that ensure gaseous exchange.
Answer: Lenticels
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F. Give reasons for the following.

Plants do not have breathing organs.
Answer: Every part of a plant (leaves, stems, and roots) can independently take in oxygen and expel carbon dioxide from its immediate surroundings. Because the gases move entirely by simple diffusion over short distances, specialized breathing organs are not required.
Energy released during anaerobic respiration is much less than energy released during aerobic respiration.
Answer: In anaerobic respiration, glucose is incompletely oxidised in the absence of oxygen, producing intermediate products like ethyl alcohol. As a result, only a tiny fraction of the chemical energy locked in glucose is released compared to aerobic respiration, where glucose is completely oxidised into carbon dioxide and water.
Plants do not take in oxygen and give out carbon dioxide during daytime. Does it mean plants do not respire during day?
Answer: No, plants respire continuously during the day. However, during the daytime, the carbon dioxide released by respiration is immediately consumed during photosynthesis, and the oxygen produced as a byproduct of photosynthesis is utilized for respiration. Because these processes balance out, there is no net intake of oxygen or release of carbon dioxide from the atmosphere.
To demonstrate that carbon dioxide is produced during respiration by plants, we use sprouted seeds and not green plants.
Answer: Sprouted seeds actively respire but do not perform photosynthesis because they lack green leaves and chlorophyll. If green plants were used in daylight, they would perform photosynthesis and consume the released carbon dioxide, preventing us from demonstrating its production.
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G. Differentiate between the following.

Gaseous exchange and cell respiration
Answer:
Gaseous Exchange (Breathing): It is a mechanical/physical process that involves taking in oxygen and expelling carbon dioxide. It occurs by simple diffusion through stomata or lenticels, and no energy is released.
Cell Respiration: It is a chemical/biochemical process that occurs inside the cells where glucose is oxidised with the help of enzymes to release energy (stored as ATP).
Aerobic and anaerobic respiration
Answer:
Aerobic Respiration
Anaerobic Respiration
Occurs in the presence of oxygen.
Occurs in the absence of oxygen.
Glucose is completely oxidised.
Glucose is oxidised incompletely.
End-products are carbon dioxide and water.
End-products are ethyl alcohol and carbon dioxide (in plants) or lactic acid (in animal cells).
High amount of energy is produced.
Very little energy is produced.
Requires mitochondria.
Does not require mitochondria (occurs in cytoplasm).
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Respiration and photosynthesis
Answer:
Respiration
Photosynthesis
Takes place in all living cells.
Takes place only in green parts of plants containing chlorophyll.
Occurs continuously (both day and night).
Occurs only in the presence of sunlight (during daytime).
Consumes oxygen and releases carbon dioxide.
Consumes carbon dioxide and releases oxygen.
Involves the breakdown of glucose.
Involves the synthesis of glucose.
Occurs inside mitochondria and cytoplasm.
Occurs inside chloroplasts.
Exergonic process (energy is released).
Endergonic process (energy is used/stored).
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H. Match the columns.

Column A
Column B
1. Ethyl alcohol
(a) Aerobic
2. Stomata
(b) Diffusion
3. Respiration in germinating seeds
© Carbon dioxide
4. Transport of respiratory gases
(d) Anaerobic respiration
5. Limewater
(e) Leaves
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Answer:
Ethyl alcohol — (d) Anaerobic respiration
Stomata — (e) Leaves
Respiration in germinating seeds — (a) Aerobic
Transport of respiratory gases — (b) Diffusion
Limewater — © Carbon dioxide
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I. Answer these questions.

Name the end-products of aerobic respiration.
Answer: Carbon dioxide (
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), water (
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), and energy (stored as ATP).
Give equation in words to represent process of respiration.
Answer:
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What is the source of oxygen for respiration in plants during daytime?
Answer: The source of oxygen is the oxygen produced as a byproduct of photosynthesis inside the chloroplasts of the plant cells.
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J. Case-based Questions

What is the difference between respiration and photosynthesis?
Answer: Respiration is an exergonic biochemical process occurring in all living cells at all times, where glucose is broken down to release carbon dioxide, water, and energy (ATP). Photosynthesis is an endergonic process occurring only in chlorophyll-containing cells during the day, where glucose is synthesized using carbon dioxide, water, and light energy, releasing oxygen.
“All plants give out oxygen during day and carbon dioxide during the night.” Do you agree with this statement? Give reason.
Answer: Yes, this statement is correct. During the day, both photosynthesis and respiration take place, but the rate of photosynthesis is much higher than respiration, resulting in a net release of oxygen. At night, photosynthesis stops in the absence of sunlight, but respiration continues, meaning the plants only consume oxygen and release carbon dioxide.
How does gaseous exchange take place in plants?
Answer: Gaseous exchange in plants takes place entirely by simple diffusion. Oxygen and carbon dioxide pass into and out of plant cells through specific specialized openings: stomata in the leaves and young stems, lenticels in the bark of old woody stems, and root hairs in the roots.
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ThinkZone

Why do green plants not need to breathe in oxygen during daytime?
Answer: During the daytime, green plants undergo photosynthesis, which produces oxygen as a waste product. A portion of this oxygen is directly utilized by the plant cells to carry out respiration, making it unnecessary for them to take in additional oxygen from the atmosphere.
If a green plant is placed in sunlight in an air-tight bell jar with a beaker containing limewater, will limewater turn milky? Why or why not?
Answer: No, the limewater will not turn milky. Although the plant produces carbon dioxide during respiration, it immediately reabsorbs it to perform photosynthesis in the presence of sunlight. Since no excess carbon dioxide accumulates in the air inside the jar, it cannot react with the limewater.
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