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Class 10 Science Chapter 5: Life Processes MCQs with answers

10 multiple-choice questions on Life Processes, each with its answer and the reason, written from the NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter.

Question 1
Carbohydrate that a green plant does not use at once is stored as its internal energy reserve in the form of
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Answer: (c) starch

Unused carbohydrate is stored as starch, the plant's energy reserve. Glycogen is the reserve in which animals store energy.

Question 2
Salivary amylase in the mouth converts
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Answer: (b) starch into simple sugar

Saliva contains salivary amylase, which breaks starch, a complex molecule, into simple sugar.

Question 3
The enzyme that can act only in the acidic medium created by hydrochloric acid in the stomach is
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Answer: (a) pepsin

The gastric glands release pepsin, a protein-digesting enzyme, and the hydrochloric acid gives the acidic medium pepsin needs. Trypsin and lipase are pancreatic enzymes.

Question 4
In a person whose bile duct is blocked, the digestion of which food is affected most?
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Answer: (c) Fats

Bile salts break large fat globules into smaller ones so that lipase can act efficiently. Without bile the fat stays in large globules and is poorly digested.

Question 5
The villi on the inner lining of the small intestine mainly
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Answer: (d) increase the surface area for absorption

Villi are finger-like projections that increase the surface area for absorption and are richly supplied with blood vessels.

Question 6
A cow has a much longer small intestine than a tiger because
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Answer: (a) the cellulose in grass needs a longer time to digest

Herbivores eating grass need a longer small intestine to digest cellulose; meat is easier to digest, so carnivores have a shorter one.

Question 7
In the first step of respiration, glucose is broken down in the cytoplasm into pyruvate. How many carbon atoms does one pyruvate molecule have?
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Answer: (b) Three

Glucose is a six-carbon molecule and pyruvate, formed from it in the cytoplasm, is a three-carbon molecule.

Question 8
During fermentation, yeast converts each pyruvate molecule into ethanol and one molecule of carbon dioxide. The ethanol molecule therefore has
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Answer: (d) two carbon atoms

Pyruvate has three carbons and carbon dioxide takes one, so ethanol has 3 − 1 = 2 carbons.

Question 9
Which product is formed both when yeast breaks down pyruvate without oxygen and when pyruvate is broken down in the mitochondria using oxygen?
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Answer: (c) Carbon dioxide

In yeast pyruvate gives ethanol and carbon dioxide; in mitochondria it gives carbon dioxide and water. Only carbon dioxide is common. Lactic acid forms in muscle.

Question 10
The energy released during cellular respiration is immediately used to make
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Answer: (d) ATP

Energy released in respiration is used at once to synthesise ATP, the energy currency of the cell.

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