Chapter 5: Life Processes

Q1. Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms?

Solution

In multicellular organisms, the body is large and complex. Diffusion can only work over short distances. Oxygen cannot reach all parts of the body by diffusion alone. Therefore, multicellular organisms need specialized organs (like lungs, heart, blood vessels) for efficient transport of oxygen and nutrients.

Q2. What are the raw materials for photosynthesis?

Solution

The raw materials for photosynthesis are:
• Carbon dioxide (CO₂) — from the atmosphere through stomata
• Water (H₂O) — absorbed from soil through roots
• Sunlight — energy source for the reaction

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in presence of sunlight and chlorophyll)

Q3. What is the difference between respiration and combustion?

Solution

Respiration:
• Biological process in living cells
• Enzyme-catalysed
• Releases energy gradually
• Produces ATP

Combustion:
• Chemical process (burning)
• No enzymes involved
• Releases energy suddenly as heat and light
• No ATP production

Q4. What is the role of the heart in the human body?

Solution

The heart is a pumping organ that:
• Pumps deoxygenated blood to the lungs for oxygenation
• Pumps oxygenated blood to all body parts
• It is a four-chambered muscular organ
• Beats about 72 times per minute
• Ensures continuous flow of blood through double circulation

Q5. What is the difference between arteries and veins?

Solution

Arteries:
• Carry oxygenated blood (except pulmonary artery)
• Carry blood away from heart
• Thick walls, no valves
• Blood flows under high pressure

Veins:
• Carry deoxygenated blood (except pulmonary vein)
• Carry blood towards heart
• Thin walls, have valves
• Blood flows under low pressure

Q6. What is the function of nephrons in the human body?

Solution

Nephrons are the functional units of the kidney. They:
• Filter blood to remove waste products
• Form urine through filtration and reabsorption
• Maintain water and salt balance in the body
• Reabsorb useful substances like glucose, amino acids
• Each kidney has about 1 million nephrons

Q7. What is the difference between aerobic and anaerobic respiration?

Solution

Aerobic respiration:
• Requires oxygen
• Complete breakdown of glucose
• Produces CO₂ + H₂O + 38 ATP
• Takes place in mitochondria

Anaerobic respiration:
• Does NOT require oxygen
• Incomplete breakdown of glucose
• Produces ethanol + CO₂ + 2 ATP (in yeast)
• Takes place in cytoplasm

Q8. How do plants transport water and nutrients?

Solution

Plants transport through two types of tissues:
• Xylem: Transports water and minerals from roots to leaves (unidirectional — upward)
• Phloem: Transports food (sugars) from leaves to other parts (bidirectional — downward and upward)

Xylem transport is driven by root pressure and transpiration pull.

Human digestive system showing major organs

Chapter 6: Control and Coordination →

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