Class 10: Science (In English) – Lesson 5. Life Processes

EXPLANATION & SUMMARY

🔵 Detailed Explanation
Introduction: The Essence of Life Processes
Living organisms differ from non-living things because they perform certain essential activities. These activities provide energy, remove wastes, and maintain internal balance. Collectively, these are called life processes. The primary ones discussed in this lesson are:

🔵 Nutrition
🟢 Respiration
🟡 Transportation
🔴 Excretion
💡 Concept: Without these processes, living beings cannot survive, grow, or reproduce.

🔵 Nutrition
Nutrition is the process of taking in food and converting it into usable energy.
Types of Nutrition
Autotrophic Nutrition

🌿
Carried out by green plants through photosynthesis.
Raw materials: Carbon dioxide, water, sunlight, chlorophyll.
Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Steps:
➡️ Absorption of light by chlorophyll.
➡️ Splitting of water (photolysis).
➡️ Reduction of CO₂ to form glucose.

✔️ Importance: Provides food and oxygen for all life.
Heterotrophic Nutrition 🧠
Organisms depend on other organisms.

Types:
🔵 Holozoic: Humans, animals (ingestion, digestion, absorption, assimilation, egestion).
🟢 Saprophytic: Fungi, bacteria (feed on dead matter).
🟡 Parasitic: Depend on hosts (e.g., Cuscuta).
✏️ Note: Humans use holozoic nutrition, involving a complete digestive system.

🟢 Human Digestive System
Mouth: Teeth and saliva (amylase) begin starch digestion.
Oesophagus: Moves food by peristalsis.
Stomach: Secretes gastric juice—HCl, pepsin, mucus; digests proteins.

Small Intestine:
➡️ Liver secretes bile (emulsifies fats).
➡️ Pancreas secretes enzymes for carbohydrates, proteins, fats.
➡️ Absorption through villi into blood.

Large Intestine: Absorbs water, forms feces.
💡 Concept: Villi increase surface area for nutrient absorption.

🟡 Respiration
Respiration releases energy by breaking down glucose.
Aerobic respiration (with O₂):
Glucose → CO₂ + H₂O + Energy (38 ATP)

Anaerobic respiration (without O₂):
➡️ In yeast: Glucose → Alcohol + CO₂ + Energy
➡️ In muscles: Glucose → Lactic acid + Energy
✔️ Application: Muscle cramps occur due to lactic acid accumulation.

Human Respiratory System:
Organs: Nose, trachea, bronchi, lungs, alveoli.
Alveoli: Site of gaseous exchange. O₂ enters blood, CO₂ exits.
Transport: Oxygen carried by haemoglobin; CO₂ as bicarbonates.
✏️ Note: Breathing and respiration are different—breathing is physical, respiration is chemical.

🔴 Transportation in Humans
Circulatory System ensures distribution of nutrients, gases, and wastes.
Heart: 4 chambers (left and right atria, left and right ventricles).
Double circulation: Blood passes twice through heart per cycle, ensuring separation of oxygenated and deoxygenated blood.

Blood vessels:
🔵 Arteries: Thick walls, carry blood away from heart.
🟢 Veins: Thin walls, valves, carry blood toward heart.
🟡 Capillaries: Exchange of materials.

Lymph: Drains excess fluid, transports fats, protects against infections.
💡 Concept: Double circulation is an advanced adaptation for efficient oxygen supply.

🟢 Transportation in Plants
Xylem: Transports water and minerals via transpiration pull and root pressure.
Phloem: Transports food from leaves to all parts (translocation).
✔️ Application: Transpiration cools plants and maintains water balance.

🟡 Excretion
Excretion removes waste products formed during metabolism.
In Humans
Organs: Kidneys, ureters, bladder, urethra.

Nephron (functional unit):
➡️ Filtration in glomerulus.
➡️ Reabsorption in tubules.
➡️ Secretion of wastes.
Result: Urine (urea, salts, water).

✔️ Dialysis: Artificial purification of blood in kidney failure.
In Plants
Wastes stored in vacuoles.
Gaseous wastes released through stomata, lenticels.
Excrete resins, gums, latex as by-products.

Conclusion
Life processes such as nutrition, respiration, transportation, and excretion are vital for maintaining life. They ensure organisms obtain energy, eliminate wastes, and maintain internal balance. Without these, survival is impossible.

🟢 Summary
Nutrition: Autotrophic (photosynthesis), heterotrophic (holozoic, saprophytic, parasitic), human digestive system.
Respiration: Aerobic and anaerobic pathways, human respiratory organs, alveoli gas exchange, haemoglobin transport.
Transportation: Humans—heart, double circulation, blood vessels, lymph; Plants—xylem, phloem, transpiration pull, translocation.
Excretion: Humans—kidneys, nephrons, urine formation; Plants—vacuoles, stomata, resins.

📝 Quick Recap
🌿 Nutrition: Plants (photosynthesis), animals (holozoic).
⚡ Respiration: Aerobic vs anaerobic; energy as ATP.
🧠 Transport: Heart and vessels in humans, xylem & phloem in plants.
💧 Excretion: Kidneys in humans, vacuoles/resins in plants.
✔️ Life processes keep organisms alive and balanced.

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QUESTIONS FROM TEXTBOOK

Question 1
The kidneys in human beings are a part of the system for
(a) nutrition
(b) respiration
(c) excretion
(d) transportation
Answer
✔️ Kidneys are part of the excretory system.
Their main function is to remove nitrogenous wastes (urea, uric acid, ammonia) from the blood.
They also maintain water–salt balance (osmoregulation) and pH balance.
Correct option: (c) excretion

Question 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
✔️ Xylem conducts water and dissolved minerals from roots to aerial parts of the plant.
Transport occurs through root pressure, capillary action, and transpiration pull.
Correct option: (a) transport of water

Question 3
The autotrophic mode of nutrition requires
(a) carbon dioxide and water
(b) chlorophyll
(c) sunlight
(d) all of the above
Answer
✔️ For photosynthesis, plants require:
Carbon dioxide and water (raw materials).
Chlorophyll (pigment to trap sunlight).
Sunlight (energy source).
Correct option: (d) all of the above

Question 4
The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm
(b) mitochondria
(c) chloroplast
(d) nucleus
Answer
✔️ Pyruvate (formed in cytoplasm during glycolysis) enters mitochondria for complete oxidation in aerobic respiration.
Reaction: Pyruvate → CO₂ + H₂O + Energy (ATP).
This is known as the Krebs cycle followed by the electron transport chain.
Correct option: (b) mitochondria

Question 5
How are fats digested in our bodies? Where does this process take place?
Answer
✔️ Digestion of fats occurs mainly in the small intestine.
➡️ Steps:
Bile (from liver) emulsifies large fat globules into tiny droplets, increasing enzyme action surface.
Pancreatic lipase enzyme breaks down emulsified fats into fatty acids and glycerol.
These products are absorbed by villi into lymph vessels.
✏️ Note: No digestion of fats occurs in mouth or stomach; it is specific to small intestine.

Question 6
What is the role of saliva in the digestion of food?
Answer
✔️ Saliva plays two important roles:
Contains salivary amylase which digests starch into maltose (sugar).
Moistens and lubricates food, making swallowing easier.
💡 Concept: Salivary digestion is the first chemical step in human digestion.

Question 7
What are the necessary conditions for autotrophic nutrition and what are its by-products?
Answer
✔️ Conditions:
Carbon dioxide, water, sunlight, and chlorophyll.
✔️ Process: Photosynthesis.
Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
✔️ By-products: Oxygen (O₂) is released; glucose is formed as the main product.

Question 8
What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
Answer
✔️ Differences:
Aerobic respiration: Uses O₂, occurs in mitochondria, complete breakdown of glucose, produces more ATP (38).
Anaerobic respiration: Does not use O₂, occurs in cytoplasm, incomplete breakdown of glucose, produces less ATP (2).
✔️ Organisms with anaerobic respiration: Yeast (alcoholic fermentation), certain bacteria, muscle cells during heavy exercise.

Question 9
How are the alveoli designed to maximise the exchange of gases?
Answer
✔️ Alveoli are tiny balloon-like sacs in the lungs with special adaptations:
Very thin walls for rapid diffusion.
Surrounded by dense network of capillaries.
Moist surface for efficient gas dissolution.
Large number (millions) providing vast surface area.
💡 Concept: These features ensure maximum oxygen intake and carbon dioxide release.

Question 10
What would be the consequences of a deficiency of haemoglobin in our bodies?
Answer
✔️ Haemoglobin binds and transports oxygen in blood.
➡️ If haemoglobin is deficient:
Less oxygen transported to cells.
Leads to tiredness, weakness, breathlessness.
Severe deficiency causes anaemia.

Question 11
Describe double circulation of blood in human beings. Why is it necessary?
Answer
✔️ Double circulation means blood passes through the heart twice in one complete cycle:
Pulmonary circulation: Right side → lungs → left side (oxygenation of blood).
Systemic circulation: Left side → body → right side (distribution of oxygenated blood and return of deoxygenated blood).
✔️ Necessity:
Keeps oxygenated and deoxygenated blood separate.
Ensures high efficiency of oxygen supply, vital for warm-blooded animals like humans.

Question 12
What are the differences between the transport of materials in xylem and phloem?
Answer
✔️ Differences:
Xylem: Transports water and minerals from roots to leaves, movement is unidirectional, passive process (does not require energy).
Phloem: Transports food (sugars) from leaves to other parts, movement is bidirectional, active process (requires energy).

Question 13
Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
Answer
✔️ Alveoli:
Structure: Tiny sacs with thin walls and rich capillary network.
Function: Exchange of O₂ and CO₂ between air and blood by diffusion.
✔️ Nephrons:
Structure: Microscopic filtration units with glomerulus and tubules.
Function: Filter blood, remove nitrogenous wastes, reabsorb useful substances, form urine.
💡 Concept: Both are structural and functional units—alveoli for respiration, nephrons for excretion.

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OTHER IMPORTANT QUESTIONS FOR EXAMS

(CBSE MODEL QUESTION PAPER)

ESPECIALLY MADE FROM THIS CHAPTER ONLY

🟢 Section A
🔒 ❓ Q1. Which process is essential for maintaining life in all living organisms?
🟢 1️⃣ Reproduction
🔵 2️⃣ Respiration
🟡 3️⃣ Movement
🟣 4️⃣ Growth
✔️ Answer: 🔵2️⃣ Respiration

🔒 ❓ Q2. Which of the following is the raw material for photosynthesis?
🟢 1️⃣ Oxygen and water
🔵 2️⃣ Carbon dioxide and water
🟡 3️⃣ Glucose and oxygen
🟣 4️⃣ Sunlight and chlorophyll
✔️ Answer: 🔵2️⃣ Carbon dioxide and water

🔒 ❓ Q3. In human beings, digestion of protein begins in the:
🟢 1️⃣ Mouth
🔵 2️⃣ Stomach
🟡 3️⃣ Small intestine
🟣 4️⃣ Large intestine
✔️ Answer: 🔵2️⃣ Stomach

🔒 ❓ Q4. Which pigment is necessary for photosynthesis?
🟢 1️⃣ Haemoglobin
🔵 2️⃣ Chlorophyll
🟡 3️⃣ Melanin
🟣 4️⃣ Auxin
✔️ Answer: 🔵2️⃣ Chlorophyll

🔒 ❓ Q5. The blood vessel that carries blood from the heart to all parts of the body is called:
🟢 1️⃣ Vein
🔵 2️⃣ Capillary
🟡 3️⃣ Artery
🟣 4️⃣ Nephron
✔️ Answer: 🟡3️⃣ Artery

🔒 ❓ Q6. The main function of stomata is:
🟢 1️⃣ Transport of food
🔵 2️⃣ Exchange of gases
🟡 3️⃣ Absorption of minerals
🟣 4️⃣ Reproduction
✔️ Answer: 🔵2️⃣ Exchange of gases

🔒 ❓ Q7. Which part of the nephron filters blood?
🟢 1️⃣ Bowman’s capsule and glomerulus
🔵 2️⃣ Ureter
🟡 3️⃣ Urethra
🟣 4️⃣ Urinary bladder
✔️ Answer: 🟢1️⃣ Bowman’s capsule and glomerulus

🔒 ❓ Q8. The transport of water and minerals in plants takes place through:
🟢 1️⃣ Phloem
🔵 2️⃣ Xylem
🟡 3️⃣ Stomata
🟣 4️⃣ Chloroplast
✔️ Answer: 🔵2️⃣ Xylem

🔒 ❓ Q9. Which component of blood helps in clotting?
🟢 1️⃣ RBCs
🔵 2️⃣ WBCs
🟡 3️⃣ Platelets
🟣 4️⃣ Plasma
✔️ Answer: 🟡3️⃣ Platelets

🔒 ❓ Q10. The breakdown of pyruvate into ethanol and carbon dioxide occurs during:
🟢 1️⃣ Aerobic respiration in mitochondria
🔵 2️⃣ Anaerobic respiration in yeast
🟡 3️⃣ Photosynthesis
🟣 4️⃣ Digestion in stomach
✔️ Answer: 🔵2️⃣ Anaerobic respiration in yeast

🔒 ❓ Q11. Assertion (A): All living organisms need energy to perform life processes.
🔒 ❓ Reason (R): Energy is obtained by the oxidation of food during respiration.
🟢 1️⃣ Both A and R are true, and R is the correct explanation of A
🔵 2️⃣ Both A and R are true, but R is not the correct explanation of A
🟡 3️⃣ A is true, but R is false
🟣 4️⃣ A is false, but R is true
✔️ Answer: 🟢1️⃣ Both A and R are true, and R is the correct explanation of A

🔒 ❓ Q12. Assertion (A): The small intestine is the site of complete digestion of food.
🔒 ❓ Reason (R): Bile juice and pancreatic juice act in the small intestine.
🟢 1️⃣ Both A and R are true, and R is the correct explanation of A
🔵 2️⃣ Both A and R are true, but R is not the correct explanation of A
🟡 3️⃣ A is true, but R is false
🟣 4️⃣ A is false, but R is true
✔️ Answer: 🟢1️⃣ Both A and R are true, and R is the correct explanation of A

🔒 ❓ Q13. Assertion (A): Arteries always carry oxygenated blood.
🔒 ❓ Reason (R): Pulmonary artery carries deoxygenated blood from the heart to the lungs.
🟢 1️⃣ Both A and R are true, and R is the correct explanation of A
🔵 2️⃣ Both A and R are true, but R is not the correct explanation of A
🟡 3️⃣ A is false, but R is true
🟣 4️⃣ A is true, but R is false
✔️ Answer: 🟡3️⃣ A is false, but R is true

🔒 ❓ Q14. Assertion (A): In plants, phloem transports food.
🔒 ❓ Reason (R): Phloem transport requires energy.
🟢 1️⃣ Both A and R are true, and R is the correct explanation of A
🔵 2️⃣ Both A and R are true, but R is not the correct explanation of A
🟡 3️⃣ A is true, but R is false
🟣 4️⃣ A is false, but R is true
✔️ Answer: 🔵2️⃣ Both A and R are true, but R is not the correct explanation of A

🔒 ❓ Q15. Assertion (A): Kidneys remove nitrogenous wastes from the blood.
🔒 ❓ Reason (R): Nephrons are the structural and functional units of kidneys.
🟢 1️⃣ Both A and R are true, and R is the correct explanation of A
🔵 2️⃣ Both A and R are true, but R is not the correct explanation of A
🟡 3️⃣ A is true, but R is false
🟣 4️⃣ A is false, but R is true
✔️ Answer: 🔵2️⃣ Both A and R are true, but R is not the correct explanation of A

🔒 ❓ Q16. What is the basic unit of kidney called?
📌 ✅ Answer: Nephron

🔒 ❓ Q17. Which blood pigment carries oxygen in human beings?
📌 ✅ Answer: Haemoglobin

🔒 ❓ Q18. What is the process of taking food into the body called?
📌 ✅ Answer: Nutrition

🔒 ❓ Q19. Name the tissue that transports food in plants.
📌 ✅ Answer: Phloem

🔒 ❓ Q20. Which cell organelle is called the powerhouse of the cell?
📌 ✅ Answer: Mitochondria

🟢 Section B (Q21–26: Very Short Answers, 2 marks each)
Question 21
What is peristalsis?
Answer
Rhythmic, wave-like muscular contractions of the alimentary canal.
Pushes food forward from oesophagus to stomach and through intestines.

Question 22
Why is transpiration important in plants?
Answer
Helps in upward movement of water and minerals.
Cools plant surface and maintains water cycle.

Question 23
State the role of hydrochloric acid in stomach.
Answer
Provides acidic medium for action of enzyme pepsin.
Kills harmful bacteria in food.

Question 24
What is the difference between breathing and respiration?
Answer
Breathing: Physical process of inhalation and exhalation.
Respiration: Biochemical process of breakdown of glucose to release energy.

Question 25
Why are capillaries suited for exchange of materials?
Answer
Thin-walled and narrow, allowing diffusion of gases and nutrients.
Dense network ensures close contact with tissues.

Question 26
What is excretion in plants?
Answer
Removal of metabolic wastes like CO₂, water, resins, gums.
Occurs through stomata, lenticels, or storage in vacuoles.

🟡 Section C (Q27–33: Short Answers, 3 marks each)
Question 27
Explain the process of photosynthesis with a balanced chemical equation.
Answer
Process by which green plants make food using CO₂, water, sunlight, chlorophyll.
Steps: Light absorption, splitting of water, reduction of CO₂, glucose formation.
Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Question 28
List three differences between arteries and veins.
Answer
Arteries: Thick walls, carry blood away from heart, high pressure.
Veins: Thin walls, carry blood to heart, valves prevent backflow.
Arteries carry oxygenated blood (except pulmonary artery), veins carry deoxygenated blood (except pulmonary vein).

Question 29
Explain the role of diaphragm in breathing.
Answer
Inhalation: Diaphragm contracts, moves downward → increases chest cavity volume → air enters lungs.
Exhalation: Diaphragm relaxes, moves upward → decreases volume → air expelled.

Question 30
Why do herbivores have a longer small intestine compared to carnivores?
Answer
Herbivores digest cellulose-rich plant food.
Require longer time and surface area for absorption.
Carnivores eat protein-rich food, digested faster, so shorter intestine.

Question 31
How does urine formation take place in nephron?
Answer
Filtration of blood in Bowman’s capsule.
Reabsorption of useful substances (glucose, water, salts).
Secretion of wastes, forming urine that passes into collecting duct.

Question 32
Give reasons:
(a) Desert plants open stomata at night.
(b) Oxygen is released during photosynthesis.
Answer
(a) To reduce water loss due to transpiration in hot day conditions.
(b) Splitting of water molecules during photosynthesis releases O₂ as by-product.

Question 33
Explain the mechanism of transport of food in phloem.
Answer
Food prepared in leaves is transported to other parts by phloem (translocation).
Movement is bidirectional.
Requires energy in form of ATP to load sucrose into sieve tubes, creating pressure gradient for flow.


Question 34
Explain the structure and working of human heart with the help of a flow sequence of blood circulation.
Answer
Human heart: Muscular organ with 4 chambers – Right atrium, Right ventricle, Left atrium, Left ventricle.
Flow sequence:
🔵 Deoxygenated blood from body → Right atrium → Right ventricle → Pulmonary artery → Lungs.
🟢 In lungs: Exchange of gases, blood becomes oxygenated.
🟡 Oxygenated blood from lungs → Pulmonary vein → Left atrium → Left ventricle → Aorta → Entire body.
Valves ensure one-way flow of blood.
Double circulation ensures separation of oxygenated and deoxygenated blood → efficient oxygen supply.
✔️ Importance: Maintains high energy output required for warm-blooded animals like humans.

Question 35
Describe the human respiratory system. Explain the process of breathing in detail.
Answer
Organs: Nose → Pharynx → Trachea (windpipe with C-shaped cartilage rings) → Bronchi → Bronchioles → Alveoli.
Breathing process:
➡️ Inhalation: Diaphragm contracts & moves down, ribs move outward → chest cavity expands → air rushes in.
➡️ Exhalation: Diaphragm relaxes & moves up, ribs fall inward → chest cavity volume decreases → air pushed out.
Gas exchange:
O₂ diffuses from alveoli into blood (higher concentration in alveoli).
CO₂ diffuses from blood into alveoli.
Transport: O₂ carried by haemoglobin, CO₂ as bicarbonates.
✔️ Breathing ensures continuous supply of oxygen for cellular respiration and removal of carbon dioxide.

Question 36
Explain the process of digestion of carbohydrates, proteins and fats in human alimentary canal with related enzymes and secretions.
Answer
Mouth: Salivary amylase breaks starch → maltose.
Stomach: Gastric juice (HCl + pepsin + mucus). Pepsin digests proteins → peptones.
Small intestine:
🔵 Bile (from liver): Emulsifies fats into droplets.
🟢 Pancreatic juice (from pancreas): Amylase (carbs → maltose), Trypsin (proteins → peptides), Lipase (fats → fatty acids & glycerol).
🟡 Intestinal juice: Final breakdown – maltase, peptidase, lipase complete digestion.
Absorption: Through villi into blood/lymph.
Large intestine: Absorbs water, undigested matter removed as feces.
✔️ Complete digestion ensures supply of glucose, amino acids, fatty acids and glycerol for body functions.

🟣 Section E (Q37–Q39: Case/Source Based, 4 marks each)
Question 37
Case: A student performs an experiment by blowing air into lime water through a straw. He observes that lime water turns milky.
Questions:
(a) Why does lime water turn milky?
(b) Write the equation of the reaction.
(c) What does this experiment prove about respiration?
Answer
(a) Lime water turns milky due to formation of calcium carbonate.
(b) Ca(OH)₂ + CO₂ → CaCO₃ + H₂O
(c) Exhaled air contains CO₂ → proves that CO₂ is a product of respiration.

Question 38
Case: A person suffers from kidney failure and is advised dialysis.
Questions:
(a) What is dialysis?
(b) How does it help in purification of blood?
(c) Name two wastes removed by dialysis.
Answer
(a) Dialysis: Artificial method of purifying blood using a dialysis machine when kidneys fail.
(b) Blood passes through semi-permeable membrane in machine → wastes diffuse out → cleaned blood returned to body.
(c) Removes urea, excess salts and water.

Question 39
Case: A potted plant is kept in sunlight for several hours. A leaf is then tested with iodine solution after removing chlorophyll.
Questions:
(a) Why is the leaf treated with alcohol before testing with iodine?
(b) Why is iodine solution used?
(c) What will be the colour change if starch is present?
(d) What does this experiment prove?
Answer
(a) Alcohol removes chlorophyll, making the leaf colourless for starch test.
(b) Iodine solution detects starch.
(c) Blue–black colour appears if starch is present.
(d) Proves that photosynthesis occurs in leaves and starch is formed as its product.

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