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Life Processes – Class 10 Science notes, important questions and MCQs

NCERT Class 10 Science, chapter 5. Notes, key terms, important questions with answers and MCQs.

Chapter overview

Life processes — nutrition, respiration, transportation and excretion — keep an organism alive by supplying energy and materials and removing wastes.

Nutrition

Autotrophs (green plants) make food by photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ in the presence of sunlight and chlorophyll.
Stomata allow gas exchange; guard cells open and close them.
Human digestion: mouth (salivary amylase), stomach (HCl, pepsin), small intestine (bile, pancreatic juice, villi absorb food).

Respiration

Aerobic: glucose → CO₂ + H₂O + much energy (in mitochondria).
Anaerobic: in yeast → ethanol + CO₂; in muscles → lactic acid (cramps).
Lungs have alveoli for gas exchange; haemoglobin carries oxygen.

Transport and excretion

Human heart has 4 chambers; double circulation keeps oxygenated and deoxygenated blood separate.
Plants: xylem carries water and minerals; phloem carries food (translocation).
Kidneys filter blood through nephrons to form urine.

Key terms

Autotrophic nutrition: making one's own food from simple substances
Villi: finger-like projections in the small intestine that increase absorption
Nephron: filtering unit of the kidney
Translocation: transport of food in phloem

Formulas

Photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (sunlight, chlorophyll)
Aerobic respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP)

Important questions with answers

Why is the rate of breathing faster in aquatic organisms than in terrestrial ones?2 marks

The amount of oxygen dissolved in water is much lower than in air, so aquatic organisms must breathe faster to get enough oxygen.

Explain double circulation in humans and why it is necessary.3 marks

Blood passes through the heart twice in one cycle: the right side sends deoxygenated blood to the lungs (pulmonary circulation) and the left side sends oxygenated blood to the body (systemic circulation). Keeping the two kinds of blood separate gives an efficient oxygen supply, needed by warm-blooded animals with high energy use.

Describe the structure and working of a nephron.5 marks

A nephron has a cup-shaped Bowman's capsule around a cluster of capillaries (the glomerulus), followed by a long tubule that opens into a collecting duct. Blood is filtered under pressure in the glomerulus; the filtrate contains water, glucose, amino acids, salts and urea. As it passes along the tubule, useful substances such as glucose, amino acids, most salts and much of the water are reabsorbed into the surrounding capillaries. The remaining liquid, urine, flows into the collecting duct, then the ureter and the urinary bladder.

Quick revision

Pepsin digests proteins in the stomach.
Bile emulsifies fats (it has no enzyme).
Xylem = water; phloem = food.
Nephron is the unit of the kidney.

Exam tips

Draw and label the human heart, alimentary canal and nephron — they are frequently asked.
Remember: arteries carry blood away from the heart, veins carry it to the heart.

Practice MCQs

The site of photosynthesis in a cell is the
1. mitochondrion
2. nucleus
3. chloroplast
4. ribosome
Show answer
Answer: (c) chloroplast. Chloroplasts contain chlorophyll.
Which tissue carries water in plants?
1. phloem
2. epidermis
3. cambium
4. xylem
Show answer
Answer: (d) xylem. Xylem.
The functional unit of the kidney is the
1. nephron
2. neuron
3. alveolus
4. villus
Show answer
Answer: (a) nephron. Nephron.
Bile helps in digestion by
1. digesting proteins
2. killing germs
3. digesting starch
4. emulsifying fats
Show answer
Answer: (d) emulsifying fats. It breaks fat into small droplets.
In human muscles, lack of oxygen during exercise produces
1. ethanol
2. CO₂ only
3. citric acid
4. lactic acid
Show answer
Answer: (d) lactic acid. Anaerobic respiration in muscles.
How many chambers does the human heart have?
1. 2
2. 3
3. 4
4. 5
Show answer
Answer: (c) 4. Two atria and two ventricles.
Why is double circulation needed in mammals?
1. to digest food faster
2. to make urine
3. to keep oxygenated and deoxygenated blood separate for high energy needs
4. to cool the body only
Show answer
Answer: (c) to keep oxygenated and deoxygenated blood separate for high energy needs. Separation gives efficient oxygen supply.
The opening and closing of stomata is controlled by
1. root hairs
2. guard cells
3. xylem
4. phloem
Show answer
Answer: (b) guard cells. Guard cells swell or shrink with water.

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Written by Kundali IQ from standard, well-established facts to help with revision. This is not an official NCERT publication; always read your textbook too.