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Science Class- 10

Class 10 - Chapter 5: Life Processes

NCERTChapter 5Solution

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

Answer: (c) Excretion.

Kidneys remove waste products such as urea, excess salts and water from the blood.

Q2. The xylem in plants are responsible for

Answer: (a) Transport of water.

Xylem tissues transport water and minerals from roots to different parts of the plant.

Q3. The autotrophic mode of nutrition requires

Answer: (d) All of the above.

Autotrophic nutrition requires carbon dioxide, water, chlorophyll and sunlight for photosynthesis.

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

Answer: (b) Mitochondria.

In aerobic respiration, pyruvate is completely oxidized in the mitochondria to produce carbon dioxide, water and energy.

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

Fat digestion takes place mainly in the small intestine.

Bile juice from the liver breaks large fat globules into smaller droplets. This process is called emulsification.

The enzyme lipase then breaks fats into fatty acids and glycerol, which are absorbed by the intestinal walls.

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

Saliva moistens and softens food, making it easier to swallow.

It contains the enzyme salivary amylase (ptyalin), which begins the digestion of starch and converts it into simple sugars.

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

Necessary Conditions:

  • Sunlight
  • Chlorophyll
  • Carbon dioxide
  • Water

By-products:

Oxygen is released as a by-product during photosynthesis.

Photosynthesis Equation:

6CO2 + 6H2O → C6H12O6 + 6O2

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

Aerobic Respiration Anaerobic Respiration
Occurs in the presence of oxygen. Occurs in the absence of oxygen.
Produces carbon dioxide, water and large amount of energy. Produces alcohol/lactic acid and less energy.
Complete breakdown of glucose. Incomplete breakdown of glucose.
Mainly occurs in mitochondria. Occurs in cytoplasm.

Examples of organisms using anaerobic respiration:

  • Yeast
  • Certain bacteria

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

Alveoli are tiny balloon-like structures present in the lungs.

  • They provide a large surface area for gas exchange.
  • Their walls are very thin.
  • They are richly supplied with blood capillaries.
  • They maintain a concentration gradient for rapid diffusion of gases.

These features help in efficient exchange of oxygen and carbon dioxide.

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

Haemoglobin carries oxygen in the blood.

A deficiency of haemoglobin causes anaemia.

Consequences:

  • Fatigue and weakness
  • Shortness of breath
  • Dizziness
  • Pale skin
  • Reduced oxygen supply to body tissues

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

In human beings, blood passes through the heart twice during one complete circulation.

Path of Blood Flow:

Body → Heart → Lungs → Heart → Body

This is called double circulation and consists of:

  1. Pulmonary circulation (heart to lungs and back)
  2. Systemic circulation (heart to body and back)

Necessity:

  • Prevents mixing of oxygenated and deoxygenated blood.
  • Ensures efficient oxygen supply to body tissues.
  • Helps maintain high energy requirements of the body.

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

Xylem Phloem
Transports water and minerals. Transports food (sugars).
Movement is mainly upward. Movement can be upward and downward.
Transport occurs through dead cells. Transport occurs through living cells.
Requires little or no energy. Requires energy (ATP).

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

Alveoli Nephrons
Present in lungs. Present in kidneys.
Thin-walled sac-like structures. Tubular filtering units.
Rich supply of blood capillaries. Rich supply of blood capillaries.
Exchange oxygen and carbon dioxide. Filter blood and form urine.
Provide a large surface area for gaseous exchange. Provide a large surface area for filtration and reabsorption.

Similarity: Both alveoli and nephrons have thin walls, extensive capillary networks and large surface areas to perform efficient exchange processes.