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CNMS ICSE - 7 Std
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Answer key

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Chapter: 05. Respiration In Plants

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SECTION A: MULTIPLE CHOICE QUESTIONS

© Mitochondria
(b) Ethyl alcohol, carbon dioxide, and energy
(b) It is the immediate source of energy for the cell.
(d) Breathing
© A part of the oxygen produced during photosynthesis is utilized for respiration.
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SECTION B: FILL IN THE BLANKS

fermentation (specifically, lactic acid fermentation)
lenticels
exergonic
ATP (or adenosine triphosphate)
soil
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SECTION C: TRUE OR FALSE

True
False. Correction: Plants carry out respiration all the time (both day and night), but photosynthesis occurs only during the daytime in the presence of sunlight.
True
False. Correction: Yeast yields ethyl alcohol because it respires anaerobically (without oxygen).
True
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SECTION D: EXPLANATION OF TERMS

Fermentation: The anaerobic respiration occurring in yeast which involves the breakdown of sugars into alcohol and carbon dioxide.
Aerobes: Organisms that use oxygen for respiration to break down glucose and release energy.
Exergonic reaction: A chemical or biochemical reaction in which energy is produced or released (such as respiration).
Cellular respiration: A biochemical process in which glucose is oxidized inside the cells in the presence of oxygen to release water, carbon dioxide, and energy stored as ATP.
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SECTION E: DIFFERENTIATE CONCEPTS

Breathing vs. Cellular Respiration:
Nature of process: Breathing is a physical/mechanical process, while cellular respiration is a biochemical process.
Energy release: No energy is released during breathing, whereas energy is released and stored as ATP during cellular respiration.
Aerobic vs. Anaerobic Respiration:
Requirement of oxygen: Aerobic respiration occurs in the presence of oxygen, while anaerobic respiration occurs in the absence of oxygen.
End-products in plant cells: The end-products of aerobic respiration are carbon dioxide and water, while the end-products of anaerobic respiration in plant cells (like yeast) are ethyl alcohol and carbon dioxide.
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SECTION F: DIAGRAM-BASED QUESTION

The limewater in the test tube will turn milky.
Sprouted/germinating seeds are used because they active respire and release carbon dioxide, but they do not perform photosynthesis (which would otherwise consume the carbon dioxide during the day, making it difficult to demonstrate its release).
The bottle is wrapped with black paper to prevent light from entering, ensuring that no photosynthesis can occur if there are any tiny green parts, and to keep the seeds in darkness.
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SECTION G: OBSERVATION-BASED & EVERYDAY USE QUESTIONS

At night, plants do not carry out photosynthesis due to the absence of sunlight, but they continue to respire. This means they take in oxygen and release carbon dioxide. Consequently, the concentration of carbon dioxide under the tree goes up at night, which can make it unhealthy or unsafe to sleep there.
Yeast respires anaerobically in the absence of oxygen. During this process, it breaks down sugar into ethyl alcohol and carbon dioxide (a process called fermentation). Because of this production of ethyl alcohol, yeast is utilized to make wine and beer.
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SECTION H: SHORT & LONG ANSWER QUESTIONS

Word Equations: ​(a) Aerobic respiration:
math
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​(b) Anaerobic respiration (in plants):
math
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Gas Exchange in different plant parts:
Leaves: Obtain oxygen through tiny pores called stomata, which open into air cavities.
Stems: Young stems use stomata, while old woody stems use lenticels located below the bark.
Roots: Root hairs extend into soil particles and absorb oxygen trapped in the air spaces between soil particles by diffusion.
Differences between Respiration and Photosynthesis (Any three):
Occurrence: Respiration takes place in all living cells, whereas photosynthesis takes place only in the green parts of plants.
Time: Respiration occurs all the time (day and night), while photosynthesis occurs only during the daytime in the presence of sunlight.
Gases: Respiration uses oxygen and releases carbon dioxide, while photosynthesis uses carbon dioxide and releases oxygen.
Glucose: Respiration involves the breakdown of glucose, while photosynthesis involves the synthesis of glucose.
Organelle: Respiration occurs in mitochondria, while photosynthesis occurs in chloroplasts.
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