Class 10th Science Chapter 5 – Life Processes – Exercises

Q1. The kidneys in human beings are a part of the system for:

(a) nutrition
(b) respiration
(c) excretion
(d) transportation

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Answer: (c) excretion

Explanation:

• Kidneys remove nitrogenous wastes such as urea, uric acid and excess salts from the blood.

• They filter blood and form urine, which is then expelled from the body.

• This process is called excretion, handled by the excretory system.

Therefore, kidneys belong to the excretory system.

Q2. The xylem in plants are responsible for:

(a) transport of water
(b) transport of food
(c) transport of amino acids
(d) transport of oxygen

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Answer: (a) transport of water

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Explanation:

• Xylem is a conducting tissue in plants responsible for the upward transport of water and minerals from the roots to different parts of the plant.

• Phloem transports food (such as sugars) prepared by leaves during photosynthesis to other parts of the plant.

Q3. The autotrophic mode of nutrition requires

(a) carbon dioxide and water
(b) chlorophyll
(c) sunlight
(d) all of the above

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Answer: (d) all of the above

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Explanation:

Autotrophic nutrition is the process by which green plants prepare their own food through photosynthesis.

Q4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in

(a) cytoplasm
(b) mitochondria
(c) chloroplast
(d) nucleus

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Answer: (b) mitochondria

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Explanation:

After glycolysis in the cytoplasm, pyruvate enters the mitochondria, where it is broken down in the presence of oxygen (aerobic respiration).

$$\text{Pyruvate}+O_2\to C{O}_2+H_{2}O+\text{Energy (ATP)}$$

Q5. How are fats digested in our bodies? Where does this process take place?

Answer:

• Fats are digested in the small intestine.

• The liver secretes bile, which is stored in the gall bladder and released into the small intestine.

• Bile breaks large fat globules into tiny droplets (emulsification), making digestion easier.

• Pancreatic lipase enzyme then converts emulsified fats into fatty acids and glycerol.

Reaction summary:

$$\text{Fat}\stackrel{\text{bile}}{\to }\text{small droplets}\stackrel{\text{lipase}}{\to }\text{fatty acids + glycerol}$$

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Q6. What is the role of saliva in the digestion of food?

Answer:

Saliva plays two important roles:

1. Moistens and softens food to make it easy to swallow.

2. Contains an enzyme called salivary amylase which breaks down starch (carbohydrate) into simple sugar (maltose).

Equation:

$$\text{Starch}\stackrel{\text{amylase}}{\to }\text{maltose}$$

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Q7. What are the necessary conditions for autotrophic nutrition and what are its by-products?

Answer:

Necessary conditions for autotrophic nutrition:

• Sunlight

• Chlorophyll

• Carbon dioxide

• Water

By-products:

$$\text{Glucose (food)}\text{and}\text{Oxygen}$$

Photosynthesis reaction:

$$6C{O}_2+6H_{2}O\stackrel{\text{sunlight, chlorophyll}}{\to }{C}_6{H}_{12}{O}_6+6O_2$$

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Q8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.

Answer:

Examples of organisms using anaerobic respiration:

• Yeast

• Certain bacteria

• Muscle cells in humans (during vigorous exercise)

Equation examples:

$$\text{Glucose}\to \text{Ethanol}+C{O}_2+\text{Energy (yeast)}$$
$$\text{Glucose}\to \text{Lactic acid}+\text{Energy (muscle cells)}$$

Q9. How are the alveoli designed to maximise the exchange of gases?

Answer:

Alveoli are designed to maximise gas exchange because:

• They are very small and numerous (millions in number), providing a very large surface area.

• They have thin walls (one cell thick) which allow faster diffusion of gases.

• They are surrounded by a network of capillaries with rich blood supply.

• They remain moist, helping gases dissolve and diffuse easily.

Result:

Oxygen diffuses into the blood, and carbon dioxide diffuses out rapidly.

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Q10. What would be the consequences of a deficiency of haemoglobin in our bodies?

Answer:

Haemoglobin carries oxygen in the blood.
If haemoglobin is deficient:

• Less oxygen will be transported to body cells.

• The person becomes tired, weak and pale.

• Severe deficiency causes anaemia.

• In extreme cases, tissues can be permanently damaged due to lack of oxygen.

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Q11. Describe double circulation of blood in human beings. Why is it necessary?

Answer:

Double circulation means that blood flows through the heart twice during one complete cycle.

Two circuits involved:

1. Pulmonary circulation

   • From heart → lungs → heart

   • Carries deoxygenated blood to lungs and returns oxygenated blood.

2. Systemic circulation

   • From heart → body → heart

   • Carries oxygenated blood to body and returns deoxygenated blood.

Why is it necessary?

• To separate oxygenated and deoxygenated blood

• For maintaining efficient supply of oxygen

• To release large amounts of energy needed by warm-blooded organisms like humans

• For proper functioning of organs

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Q12. What are the differences between the transport of materials in xylem and phloem?

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Q13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.

Conclusion

Both alveoli and nephrons:

• Provide large surface area

• Have thin membranes

• Are highly vascular (rich blood supply)