10th Life Processes NCERT Solution

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

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

Answer: (c) excretion.

2. The xylem in plants are responsible for

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

Answer: (a) transport of water.

3. The autotrophic mode of nutrition requires

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

Answer: (d) all of the above.

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

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

Answer: (b) mitochondria.

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

Fats are emulsified by bile salts in the small intestine, breaking large globules into tiny droplets. Pancreatic lipase then hydrolyzes these droplets into fatty acids and glycerol. This entire process occurs in the small intestine.

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

Saliva moistens and lubricates food, forming a bolus for swallowing. It contains salivary amylase, which begins the chemical digestion of starch into maltose.

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

Autotrophic nutrition requires carbon dioxide, water, sunlight, and chlorophyll. Through photosynthesis, plants produce glucose and release oxygen as a by-product.

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

Aerobic respiration uses oxygen to fully oxidize glucose, yielding about 36–38 ATP molecules per glucose. Anaerobic respiration occurs without oxygen, yielding only 2 ATP per glucose and producing lactic acid in animals or ethanol and CO₂ in yeast. Yeast, some bacteria (e.g., Clostridium), and muscle cells under strenuous exercise perform anaerobic respiration.

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

Alveoli have extremely thin (one-cell-thick) walls and are surrounded by dense capillary networks. Their spherical shape and enormous collective surface area, along with a moist lining, minimize diffusion distance and maximize gas exchange efficiency.

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

Haemoglobin deficiency leads to reduced oxygen-carrying capacity of blood, causing anemia. Symptoms include fatigue, weakness, shortness of breath, and pallor due to insufficient oxygen delivery to tissues.

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

In double circulation, deoxygenated blood from the right ventricle travels via the pulmonary artery to the lungs for oxygenation and returns via the pulmonary vein to the left atrium. The left ventricle then pumps oxygenated blood through the aorta into systemic circulation, delivering oxygen to body tissues, and returns deoxygenated blood to the right atrium. This separation maintains high systemic pressure for efficient tissue perfusion and prevents mixing of oxygenated and deoxygenated blood.

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

• Xylem transports water and dissolved minerals unidirectionally from roots to aerial parts; it consists of dead, lignified cells and relies on transpiration pull.
• Phloem transports organic solutes (mainly sucrose) bidirectionally between sources (e.g., leaves) and sinks (e.g., roots, fruits); it consists of living sieve tubes and companion cells and uses active transport during loading and unloading.

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

• Alveoli are tiny air sacs with thin epithelium and rich capillary networks; they facilitate passive diffusion of O₂ into blood and CO₂ out.
• Nephrons consist of the glomerulus enclosed in Bowman's capsule and a renal tubule (proximal tubule, loop of Henle, distal tubule, collecting duct). They perform filtration (of plasma under pressure), selective reabsorption (of water, ions, nutrients), and secretion (of waste and excess ions) to form urine.

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