CBSE Class 10 Science (2026–27)
Chapter 5: Life Processes
20 Important Questions and Answers
1. What are life processes? Why are they essential for living organisms?
Answer:
Life processes are the basic activities performed by living organisms to maintain and sustain life. These include nutrition, respiration, transportation, and excretion. Through nutrition, organisms obtain energy and raw materials for growth and repair. Respiration releases energy from food. Transportation helps in the movement of nutrients, gases, and wastes throughout the body. Excretion removes harmful metabolic wastes. Without these processes, cells would not receive energy or nutrients, and waste products would accumulate, causing damage. Thus, life processes ensure survival, growth, reproduction, and proper functioning of all living organisms.
2. Differentiate between autotrophic and heterotrophic nutrition.
Answer:
Autotrophic nutrition is the mode of nutrition in which organisms prepare their own food from simple inorganic substances like carbon dioxide and water using sunlight. Green plants and some bacteria are autotrophs. Heterotrophic nutrition is the mode in which organisms depend on other organisms for food. Animals, fungi, and most bacteria are heterotrophs. Autotrophs contain chlorophyll and perform photosynthesis, while heterotrophs lack chlorophyll. Heterotrophic nutrition may be holozoic, saprophytic, or parasitic. Thus, the major difference lies in the ability to synthesize food independently.
3. Explain the process of photosynthesis.
Answer:
Photosynthesis is the process by which green plants prepare food in the presence of sunlight. It occurs mainly in the leaves containing chlorophyll. During photosynthesis, carbon dioxide enters through stomata, and water is absorbed by roots and transported to leaves. Chlorophyll captures solar energy and converts carbon dioxide and water into glucose. Oxygen is released as a by-product. The glucose produced is either used immediately for energy or stored as starch. Photosynthesis is important because it provides food for all living organisms directly or indirectly and maintains the oxygen-carbon dioxide balance in nature.
4. What is the role of stomata in plants?
Answer:
Stomata are tiny pores present mainly on the lower surface of leaves. They are surrounded by guard cells that regulate their opening and closing. Stomata perform two important functions. First, they allow the exchange of gases between the plant and the atmosphere. Carbon dioxide enters for photosynthesis, while oxygen exits. Second, they help in transpiration, the loss of water vapor from leaves. This process creates a pull that helps transport water and minerals from roots to different parts of the plant. Thus, stomata play a vital role in photosynthesis, respiration, and water regulation.
5. Describe the human digestive system.
Answer:
The human digestive system consists of the alimentary canal and associated glands. Digestion begins in the mouth, where food is chewed and mixed with saliva. The food then passes through the oesophagus to the stomach, where proteins begin digestion. In the small intestine, bile from the liver and pancreatic juices help digest fats, proteins, and carbohydrates completely. Nutrients are absorbed through villi into the bloodstream. The undigested food moves to the large intestine, where water is absorbed. Finally, waste is expelled through the rectum and anus. This system ensures proper digestion and absorption of nutrients.
6. Explain the role of hydrochloric acid in the stomach.
Answer:
Hydrochloric acid (HCl) is secreted by the glands present in the stomach lining. It creates an acidic medium necessary for the activation of the enzyme pepsin, which digests proteins. The acidic environment also kills many harmful microorganisms present in food, preventing infections. Additionally, HCl helps in breaking down food particles into simpler forms, making digestion easier. However, the stomach is protected from the harmful effects of this acid by a mucus lining. Thus, hydrochloric acid plays an essential role in digestion and protection against pathogens.
7. What is respiration? Why is it important?
Answer:
Respiration is the biological process through which food is broken down to release energy required for various life activities. During respiration, glucose reacts with oxygen to produce carbon dioxide, water, and energy. This energy is stored in the form of ATP and is used for growth, movement, repair, and other cellular functions. Respiration occurs continuously in all living cells. It can be aerobic, requiring oxygen, or anaerobic, occurring without oxygen. Since all life processes require energy, respiration is considered one of the most important activities for the survival of organisms.
8. Differentiate between aerobic and anaerobic respiration.
Answer:
Aerobic respiration occurs in the presence of oxygen and results in the complete breakdown of glucose into carbon dioxide and water. It releases a large amount of energy. Anaerobic respiration occurs in the absence of oxygen and causes incomplete breakdown of glucose. It produces less energy along with products such as lactic acid or alcohol and carbon dioxide. Aerobic respiration mainly takes place in mitochondria, while anaerobic respiration occurs in the cytoplasm. Humans normally perform aerobic respiration, but muscle cells may undergo anaerobic respiration during vigorous exercise.
9. Explain the mechanism of breathing in humans.
Answer:
Breathing involves inhalation and exhalation. During inhalation, the diaphragm contracts and moves downward while the ribs move upward and outward. This increases the volume of the chest cavity, reducing air pressure inside the lungs. As a result, air enters the lungs. During exhalation, the diaphragm relaxes and moves upward, while the ribs move downward and inward. This decreases the chest cavity volume, increasing pressure inside the lungs and forcing air out. This process ensures a continuous supply of oxygen and removal of carbon dioxide from the body.
10. How does transportation occur in human beings?
Answer:
Transportation in humans is carried out by the circulatory system, which consists of the heart, blood, and blood vessels. The heart pumps blood throughout the body. Blood carries oxygen, nutrients, hormones, and other substances to cells and removes carbon dioxide and wastes. Arteries carry blood away from the heart, veins return blood to the heart, and capillaries allow exchange of materials between blood and tissues. This transportation system ensures that every cell receives essential substances and that waste products are removed efficiently, helping maintain normal body functions.
11. What is double circulation? Why is it advantageous?
Answer:
Double circulation refers to the movement of blood through the heart twice during one complete circulation. In humans, deoxygenated blood goes from the heart to the lungs for oxygenation and returns to the heart. It is then pumped to the rest of the body. This involves pulmonary circulation and systemic circulation. Double circulation prevents the mixing of oxygenated and deoxygenated blood, ensuring efficient oxygen supply to tissues. It also helps maintain high blood pressure in the systemic circuit, allowing rapid transport of nutrients and oxygen throughout the body.
12. Describe the structure and functions of the human heart.
Answer:
The human heart is a muscular organ located in the chest cavity. It has four chambers: two atria and two ventricles. The right side receives deoxygenated blood from the body and pumps it to the lungs. The left side receives oxygenated blood from the lungs and pumps it to the body. Valves prevent the backward flow of blood. The heart continuously pumps blood through rhythmic contractions called heartbeats. Its main function is to maintain circulation, ensuring the transport of oxygen, nutrients, hormones, and waste materials throughout the body.
13. What are xylem and phloem? State their functions.
Answer:
Xylem and phloem are vascular tissues in plants responsible for transportation. Xylem transports water and minerals absorbed by roots to different parts of the plant. It also provides mechanical support. Phloem transports food prepared in the leaves through photosynthesis to all plant parts, including roots, stems, fruits, and growing tissues. The movement of food through phloem is called translocation. Together, these tissues form the plant’s transport system and ensure the distribution of essential substances needed for growth, development, and survival.
14. Explain transpiration and its significance.
Answer:
Transpiration is the process by which plants lose water in the form of water vapor through stomata present on leaves. This process helps create a suction force called transpiration pull, which aids in the upward movement of water and minerals from roots to leaves. Transpiration also helps cool the plant and maintain temperature balance. It contributes to the water cycle by releasing moisture into the atmosphere. Although excessive transpiration may cause water loss, under normal conditions it is essential for efficient transport and overall plant health.
15. What is excretion? Why is it necessary?
Answer:
Excretion is the process of removing metabolic waste products from the body. During various life processes, substances such as urea, carbon dioxide, excess salts, and water are produced. If these wastes accumulate, they can become toxic and damage cells and tissues. Excretion helps maintain a healthy internal environment by eliminating harmful substances. In humans, the kidneys, lungs, skin, and liver participate in excretion. This process is necessary to maintain homeostasis, regulate body fluid composition, and ensure proper functioning of all organs and systems.
16. Describe the structure and function of nephrons.
Answer:
Nephrons are the structural and functional units of the kidneys. Each kidney contains millions of nephrons. A nephron consists of Bowman’s capsule, glomerulus, tubules, and collecting ducts. Blood is filtered in the glomerulus, and useful substances such as glucose, amino acids, and water are reabsorbed into the bloodstream. Excess water, salts, and nitrogenous wastes remain in the filtrate and form urine. The urine is then collected and transported to the urinary bladder. Nephrons play a crucial role in excretion and maintaining water and salt balance in the body.
17. How do plants excrete waste materials?
Answer:
Plants do not have a specialized excretory system like animals. They remove gaseous wastes such as oxygen and carbon dioxide through stomata and lenticels. Excess water is removed through transpiration. Some waste substances are stored in leaves, bark, fruits, and old tissues, which are later shed. Plants may also store wastes in vacuoles or convert them into harmless substances such as gums, resins, and latex. Thus, plants use various methods to eliminate or store waste products without requiring specialized excretory organs.
18. Why is the small intestine considered the main site of digestion and absorption?
Answer:
The small intestine is the main site of digestion and absorption because it receives digestive juices from the liver and pancreas. These juices contain enzymes and bile that complete the digestion of carbohydrates, proteins, and fats. The inner lining of the small intestine has numerous finger-like projections called villi, which increase the surface area for absorption. Nutrients such as glucose, amino acids, fatty acids, vitamins, and minerals are absorbed through the villi into the bloodstream. Therefore, the small intestine plays a key role in providing nutrients to the body.
19. What is the importance of blood in transportation?
Answer:
Blood is a fluid connective tissue that performs several transport functions. It carries oxygen from the lungs to body tissues and transports carbon dioxide back to the lungs. Blood also delivers nutrients absorbed from the digestive system to cells. Hormones secreted by glands are transported through blood to target organs. Additionally, blood carries waste products to excretory organs such as kidneys and skin. White blood cells protect the body from infections, while platelets help in clotting. Thus, blood is essential for maintaining coordination and proper functioning of the body.
20. Explain the relationship between photosynthesis and respiration.
Answer:
Photosynthesis and respiration are complementary processes. During photosynthesis, green plants use carbon dioxide and water to produce glucose and oxygen in the presence of sunlight. During respiration, organisms use glucose and oxygen to release energy, producing carbon dioxide and water as by-products. The products of one process become the raw materials for the other. Photosynthesis stores solar energy in the form of food, while respiration releases that stored energy for life activities. Together, these processes maintain the balance of oxygen and carbon dioxide in nature and support life on Earth.