Life Processes – important questions for Boards 2027
CBSE Class 10 Science
Carbohydrates not used immediately by a plant are stored mainly as: (A) Protein (B) Starch (C) Cellulose (D) Fatty acids
Answer
(B) Starch — carbohydrates which are not used immediately are stored in the form of starch, which serves as the internal energy reserve.
Distinguish between autotrophs and heterotrophs in terms of the food materials they use. Give one example of each.
Answer
Some organisms use simple food material obtained from inorganic sources in the form of carbon dioxide and water. These organisms, the autotrophs, include green plants and some bacteria. Other organisms utilise complex substances; heterotrophic organisms include animals and fungi.
State what chloroplasts contain. Describe the role of stomata in gas exchange during photosynthesis and identify other plant surfaces across which gas exchange occurs.
Answer
1. Chloroplasts are cell organelles in some leaf cells and contain chlorophyll. 2. Stomata are tiny pores on the surface of leaves; massive amounts of gaseous exchange take place through them for photosynthesis. Guard cells control the opening and closing of each pore. 3. Gas exchange also occurs across the surfaces of stems, roots and leaves.
State the storage form of some excess energy in humans. Then list the main events of photosynthesis in sequence and explain, using desert plants as an example, why the steps need not occur immediately one after another.
Answer
Photosynthesis fulfils the carbon and energy requirements of autotrophic organisms by converting carbon dioxide and water into carbohydrates. 1. Some of the energy derived from food in humans is stored in the body in the form of glycogen. 2. First, chlorophyll absorbs light energy. 3. Next, light energy is converted into chemical energy, and water molecules split into hydrogen and oxygen. 4. Finally, carbon dioxide is reduced to carbohydrates. These steps need not occur one after another immediately: desert plants take up carbon dioxide at night and prepare an intermediate, which is acted upon by energy absorbed by chlorophyll during the day. Thus, the stages of photosynthesis can occur at different times.
Name two factors on which an organism’s form of nutrition depends.
Answer
The form of nutrition differs depending on the type and availability of food material as well as how it is obtained by the organism.
What role do enzymes play in the nutrition of heterotrophs? Explain how heterotrophs depend on autotrophs, giving two examples of heterotrophs.
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Describe how ATP is formed from ADP and inorganic phosphate during respiration. State how much energy is released when its terminal phosphate linkage is broken, and give two cellular processes that use ATP.
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Describe the role of salivary amylase in digestion. Then state the substances released by the gastric glands and explain the roles of hydrochloric acid, pepsin and mucus. Where does complete digestion of carbohydrates, proteins and fats occur, and which organs provide secretions to assist it?
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How do fungi such as bread mould obtain nutrition?
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How does photosynthesis fulfil the carbon and energy requirements of autotrophs? State the raw materials and conditions needed to produce carbohydrates.
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71 more probable questions in this chapter, every one with a full answer.
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