Chapter 5: Life Processes

Science · CBSE Class 10 · NCERT Solutions

📖 Chapter 5 — Life Processes (CBSE Class 10 Science): Detailed notes — nutrition, respiration, transportation and excretion in plants and animals.

Chapter 5 — Life Processes

🌱 1. What are Life Processes?

The basic functions performed by living organisms to maintain life: nutrition, respiration, transportation and excretion (plus control & reproduction).

🍽️ 2. Nutrition

Autotrophic (plants): make own food by photosynthesis — 6CO₂ + 6H₂O →(sunlight, chlorophyll)→ C₆H₁₂O₆ + 6O₂. Occurs in chloroplasts; gases exchanged via stomata.
Heterotrophic: saprophytic (fungi), parasitic (Cuscuta), holozoic (Amoeba, humans).
Human digestion: Mouth (saliva → amylase digests starch) → Stomach (HCl + pepsin digests protein) → Small intestine (bile emulsifies fat; pancreatic + intestinal juices complete digestion) → absorption by villi → egestion.

🫁 3. Respiration

Glucose is broken down to release energy (ATP). Glycolysis (in cytoplasm): glucose → pyruvate. Then:

Aerobic (with O₂)	Anaerobic (without O₂)
in mitochondria → CO₂ + H₂O + much energy	in cytoplasm → lactic acid (muscles) OR ethanol + CO₂ (yeast) + little energy

Human respiratory system: nostrils → trachea → bronchi → lungs → alveoli (thin-walled, large surface, capillary-rich) where O₂/CO₂ exchange occurs. Haemoglobin in blood carries O₂.

🩸 4. Transportation

Human heart: 4 chambers (2 atria, 2 ventricles). Double circulation — blood passes through the heart twice (pulmonary: heart↔lungs; systemic: heart↔body). Keeps oxygenated & deoxygenated blood separate.
Blood vessels: arteries (carry blood away, thick walls), veins (bring blood back, valves), capillaries (exchange). Lymph also transports.
In plants: Xylem — water & minerals upward (transpiration pull, dead cells). Phloem — food (sucrose) both ways (translocation, uses ATP, living cells).

💧 5. Excretion

Human excretory system: kidneys (filtering units = nephrons: glomerulus filters blood, tubule reabsorbs useful substances), ureters, urinary bladder, urethra → urine. Plants excrete via stomata, falling leaves, gums/resins.

🧠 Remember: Photosynthesis needs sunlight+chlorophyll+CO₂+water → O₂. Glycolysis in cytoplasm; pyruvate breakdown in mitochondria. Xylem=water(dead), Phloem=food(living). Nephron=kidney's filter. Double circulation.

⭐ Exam Tips: ① Photosynthesis (equation, conditions, stomata). ② Human digestion (enzymes). ③ Aerobic vs anaerobic; alveoli. ④ Double circulation; heart chambers. ⑤ Xylem vs phloem. ⑥ Nephron & urine formation.

📘 Textbook Question Answers

Q1-4MCQs: kidney system; xylem; autotrophic needs; pyruvate breakdown.

Q1: (c) excretion. Q2: (a) transport of water. Q3: (d) all of the above (CO₂, water, chlorophyll, sunlight). Q4: (b) mitochondria.

Q5How are fats digested and where?

Fats are digested in the small intestine. Bile (from the liver) emulsifies large fat globules into small droplets, then the enzyme lipase (from pancreatic and intestinal juice) breaks them into fatty acids and glycerol.

Q6-7Role of saliva; conditions & by-products of autotrophic nutrition.

Q6: Saliva moistens food and contains salivary amylase, which breaks down starch into sugar (maltose). Q7: Conditions for photosynthesis: sunlight, chlorophyll, CO₂ and water. By-product: oxygen (glucose is stored as starch).

Q8Aerobic vs anaerobic respiration; name anaerobic organisms.

Aerobic: occurs with oxygen, in mitochondria, complete breakdown of glucose → CO₂ + H₂O + a large amount of energy. Anaerobic: without oxygen, in cytoplasm, incomplete breakdown → lactic acid (in muscles) or ethanol + CO₂ (in yeast) + a small amount of energy. Anaerobic organisms: yeast, some bacteria.

Q9-10How alveoli maximise gas exchange; effect of haemoglobin deficiency.

Q9: Alveoli are balloon-like, thin-walled, very numerous (large surface area) and surrounded by a network of blood capillaries — maximising gas exchange. Q10: Haemoglobin carries oxygen; its deficiency causes anaemia, leading to less oxygen supply, tiredness and breathlessness.

Q11Describe double circulation and why it is necessary.

In double circulation, blood passes through the heart twice in one cycle: the pulmonary circuit (heart → lungs → heart) and the systemic circuit (heart → body → heart). It is necessary to keep oxygenated and deoxygenated blood separate, ensuring an efficient oxygen supply — important for warm-blooded animals with high energy needs.

Q12Differences between transport in xylem and phloem.

Xylem: transports water and minerals upward (one direction) using transpiration pull (physical force), through dead cells; no energy needed. Phloem: transports food (sucrose) in both directions (translocation), through living cells, using energy (ATP).

Q13Compare alveoli (lungs) and nephrons (kidneys).

Alveoli are thin-walled air sacs with a large surface area and rich capillary supply for gaseous exchange (O₂ in, CO₂ out). Nephrons are filtering units with a glomerulus and tubule that filter blood and reabsorb useful materials to form urine. Both have thin membranes and a rich blood supply, but alveoli exchange gases while nephrons filter waste.

Extra practice (4× the textbook) — MCQ, short answer & long answer.

🎯 Extra MCQ

1The pigment that traps light energy is —

Chlorophyll.

2Which enzyme in the stomach digests protein?

Pepsin.

3The exit for undigested food is —

The anus (egestion).

4The upper chambers of the heart are —

Atria (auricles).

📝 Short Answer

5Why is small intestine long?

To provide a large surface area (with villi) for complete digestion and absorption of food.

6Why do we get cramps in muscles after heavy exercise?

Due to anaerobic respiration producing lactic acid, which accumulates in muscles.

7What is transpiration? Give one use.

Loss of water vapour from plant leaves; it creates a suction (transpiration pull) that draws water up and cools the plant.

8What is the role of HCl in the stomach?

It kills germs, makes the medium acidic for pepsin to act, and helps digest protein.

9Name the two circuits of double circulation.

Pulmonary circulation (heart–lungs) and systemic circulation (heart–body).

📖 Long Answer

10Describe the process of photosynthesis with its equation.

In the presence of sunlight and chlorophyll, green plants combine carbon dioxide (from air, via stomata) and water (from roots) to make glucose and release oxygen: 6CO₂ + 6H₂O →(sunlight/chlorophyll)→ C₆H₁₂O₆ + 6O₂. Glucose is stored as starch.

11Explain urine formation in the nephron.

Blood is filtered at the glomerulus; the filtrate passes into the tubule where useful substances (glucose, salts, water) are reabsorbed into the blood. The remaining waste (urea, excess salts, water) forms urine, which passes to the bladder.

12Describe the human digestive system briefly.

Food passes: mouth (amylase digests starch) → oesophagus → stomach (HCl + pepsin digest protein) → small intestine (bile + pancreatic + intestinal juices complete digestion; villi absorb nutrients) → large intestine (absorbs water) → anus (egestion of waste).

13How is respiration in plants different from that in animals?

Plants exchange gases through stomata/lenticels and there is no special transport system for gases (each part respires on its own); the rate is slower. Animals have specialised respiratory organs (lungs/gills) and blood to transport gases, with a higher rate of respiration.

14Distinguish arteries from veins.

Arteries carry blood away from the heart, have thick elastic walls, no valves, and carry oxygenated blood (except pulmonary artery). Veins bring blood back to the heart, have thin walls with valves, and carry deoxygenated blood (except pulmonary vein).

15Why is separation of oxygenated and deoxygenated blood important in mammals?

Because mammals are warm-blooded and need a lot of energy; separation ensures a highly efficient supply of oxygen to tissues, supporting their high metabolic rate.