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Life Processes: CBSE Class 10 Biology practice questions

Practise 50 questions on Life Processes, free, with an explanation for each answer.

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Sample questions

A human is a large multi-cellular organism. Why is simple diffusion not enough to meet its oxygen needs?

A single cell beside a block of many cells
  1. Oxygen is not soluble in body fluids at all
  2. Many cells are not in direct contact with the surroundings, so oxygen would reach them far too slowly
  3. Diffusion works only for carbon dioxide, not for oxygen
  4. Cells in multi-cellular organisms do not need oxygen
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B. Many cells are not in direct contact with the surroundings, so oxygen would reach them far too slowly

In a single-celled organism the whole surface touches the environment, so diffusion is enough. In a large body most cells are far from the surface, so simple diffusion cannot supply them. That creates the need for specialised organs and a transport system. Oxygen does dissolve and diffuse, and cells certainly need it, so the other options are false.

What is the role of hydrochloric acid in the stomach?

Gastric glands in the stomach wall releasing hydrochloric acid and pepsin, with a protective mucus layer
  1. It creates an acidic medium that helps the enzyme pepsin to act
  2. It digests fats into fatty acids
  3. It makes the food alkaline
  4. It protects the stomach lining from digestion
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A. It creates an acidic medium that helps the enzyme pepsin to act

Hydrochloric acid creates the acidic medium in which pepsin, the protein-digesting enzyme, works best. Mucus, not the acid, protects the stomach lining. Fats are digested later in the small intestine, where the food is made alkaline (by bile), not in the stomach.

Two plants were kept in the dark. Then they were placed under bell-jars in sunlight. Jar (a) had a watch-glass of potassium hydroxide (KOH). Jar (b) had no KOH. Which leaf shows more starch, and why?

Two bell jars over potted plants: one with a dish of potassium hydroxide inside, one without
  1. Leaf (b), because KOH in jar (a) absorbs carbon dioxide so less photosynthesis happens there
  2. Leaf (a), because KOH adds nutrients
  3. Both the same, because starch forms in the dark
  4. Leaf (a), because KOH absorbs oxygen
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A. Leaf (b), because KOH in jar (a) absorbs carbon dioxide so less photosynthesis happens there

KOH absorbs carbon dioxide. The plant in jar (a) has no CO2, so it cannot photosynthesise and makes little or no starch. The plant in jar (b) has CO2 and makes starch. This shows that carbon dioxide is essential for photosynthesis.

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