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BSEB Chapter 6 · CBSE Chapter 5Chapter 6Chapter 5: Life Processes

Class 10 Science · MCQs with answers

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  1. What is the nutrition of organisms that make their own food called?

    1. (A) Heterotrophic nutrition
    2. (B) Parasitic nutrition
    3. (C) Autotrophic nutrition
    4. (D) Saprophytic nutrition
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    Correct answer: (C) Autotrophic nutrition

    Explanation: Green plants make their own food by photosynthesis, so their nutrition is autotrophic. Organisms that depend on others for food are heterotrophs.

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  2. What are the raw materials for photosynthesis?

    1. (A) Oxygen and glucose
    2. (B) Carbon dioxide and water
    3. (C) Nitrogen and water
    4. (D) Oxygen and water
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    Correct answer: (B) Carbon dioxide and water

    Explanation: In the presence of chlorophyll and sunlight, plants make glucose from carbon dioxide and water, releasing oxygen.

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  3. Where does the oxygen released in photosynthesis come from?

    1. (A) From carbon dioxide
    2. (B) From glucose
    3. (C) From the soil
    4. (D) From splitting water molecules
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    Correct answer: (D) From splitting water molecules

    Explanation: Light energy splits water molecules into hydrogen and oxygen. This oxygen is released into the air, and the hydrogen is used to reduce carbon dioxide to carbohydrate.

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  4. What controls the opening and closing of stomata in a leaf?

    1. (A) Xylem
    2. (B) Root hairs
    3. (C) Guard cells
    4. (D) Phloem
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    Correct answer: (C) Guard cells

    Explanation: Each stoma is surrounded by two guard cells. When they fill with water they swell and the stoma opens; when they lose water they shrink and it closes.

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  5. What colour appears when iodine solution is added to test a leaf for starch?

    1. (A) Blue-black
    2. (B) Red
    3. (C) Yellow
    4. (D) Green
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    Correct answer: (A) Blue-black

    Explanation: Starch gives a blue-black colour with iodine. This shows that photosynthesis has taken place in the leaf.

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  6. Which enzyme in saliva converts starch into sugar?

    1. (A) Pepsin
    2. (B) Lipase
    3. (C) Trypsin
    4. (D) Salivary amylase
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    Correct answer: (D) Salivary amylase

    Explanation: Salivary amylase (ptyalin) starts breaking down complex starch into simple sugar right in the mouth.

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  7. Which enzyme digests proteins in the stomach?

    1. (A) Amylase
    2. (B) Pepsin
    3. (C) Lipase
    4. (D) Bile
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    Correct answer: (B) Pepsin

    Explanation: The gastric glands of the stomach produce pepsin, which digests proteins.

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  8. What is the role of hydrochloric acid in the stomach?

    1. (A) To make the medium acidic so that pepsin can act
    2. (B) To emulsify fats
    3. (C) To change starch into sugar
    4. (D) To absorb water
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    Correct answer: (A) To make the medium acidic so that pepsin can act

    Explanation: HCl creates the acidic medium that pepsin needs to work. It also kills many germs that enter with food.

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  9. How does bile help in the digestion of fats?

    1. (A) By changing fat directly into glucose
    2. (B) By digesting proteins
    3. (C) By breaking fat into small globules (emulsification)
    4. (D) By making the medium acidic
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    Correct answer: (C) By breaking fat into small globules (emulsification)

    Explanation: Bile from the liver breaks large fat globules into small ones, so enzymes can act on them easily. It also makes the medium alkaline.

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  10. What is the job of the finger-like projections (villi) on the inner wall of the small intestine?

    1. (A) To grind food
    2. (B) To increase the surface area for absorption
    3. (C) To make bile
    4. (D) To make acid
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    Correct answer: (B) To increase the surface area for absorption

    Explanation: Villi increase the surface area for absorption. They contain blood vessels that carry the digested food to every cell of the body.

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  11. Which enzyme in pancreatic juice digests emulsified fats?

    1. (A) Trypsin
    2. (B) Pepsin
    3. (C) Salivary amylase
    4. (D) Lipase
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    Correct answer: (D) Lipase

    Explanation: In pancreatic juice, trypsin digests proteins and lipase digests emulsified fats.

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  12. What products does anaerobic respiration in yeast make?

    1. (A) Lactic acid and energy
    2. (B) Carbon dioxide, water and energy
    3. (C) Ethanol, carbon dioxide and energy
    4. (D) Oxygen and glucose
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    Correct answer: (C) Ethanol, carbon dioxide and energy

    Explanation: Without oxygen, yeast converts pyruvate into ethanol and carbon dioxide. This is called fermentation.

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  13. After running fast, muscle cramps are caused by the build-up of what?

    1. (A) Lactic acid
    2. (B) Ethanol
    3. (C) Carbon dioxide
    4. (D) Glucose
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    Correct answer: (A) Lactic acid

    Explanation: When oxygen runs short, pyruvate in muscle cells changes into lactic acid. The build-up of lactic acid causes cramps.

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  14. In which part of the cell does the first step of respiration, glucose breaking down into pyruvate, take place?

    1. (A) Mitochondria
    2. (B) Nucleus
    3. (C) Chloroplast
    4. (D) Cytoplasm
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    Correct answer: (D) Cytoplasm

    Explanation: Glucose (6 carbons) breaks down into pyruvate (3 carbons) in the cytoplasm. With oxygen present, the next steps take place in the mitochondria.

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  15. What is called the "energy currency" of the cell?

    1. (A) Glucose
    2. (B) ATP
    3. (C) Pyruvate
    4. (D) Haemoglobin
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    Correct answer: (B) ATP

    Explanation: The energy released in respiration is stored as ATP molecules. Whenever a cell needs energy, it gets it by breaking down ATP.

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  16. Where does the exchange of gases take place in human lungs?

    1. (A) Alveoli
    2. (B) Trachea
    3. (C) Nostrils
    4. (D) Larynx
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    Correct answer: (A) Alveoli

    Explanation: Alveoli are tiny balloon-like sacs with thin walls covered by a network of blood capillaries. This is where oxygen enters the blood and carbon dioxide leaves it.

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  17. What mainly carries oxygen in human blood?

    1. (A) Plasma
    2. (B) Platelets
    3. (C) Haemoglobin
    4. (D) White blood cells
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    Correct answer: (C) Haemoglobin

    Explanation: Haemoglobin, the pigment in red blood cells, binds oxygen and carries it from the lungs to the body's tissues.

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  18. How many chambers does a fish's heart have?

    1. (A) 1
    2. (B) 2
    3. (C) 3
    4. (D) 4
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    Correct answer: (B) 2

    Explanation: A fish's heart has two chambers, and blood passes through the heart only once in each circuit. Humans, birds and other mammals have four-chambered hearts.

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  19. Which blood vessels carry blood from the heart to the different organs of the body?

    1. (A) Veins
    2. (B) Lymph vessels
    3. (C) Capillaries only
    4. (D) Arteries
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    Correct answer: (D) Arteries

    Explanation: Arteries carry blood from the heart to the organs. Blood flows under high pressure, so their walls are thick and elastic. Veins bring blood back to the heart.

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  20. Which blood cells help form a clot when there is an injury?

    1. (A) Red blood cells
    2. (B) White blood cells
    3. (C) Platelets
    4. (D) Nerve cells
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    Correct answer: (C) Platelets

    Explanation: Platelets form a clot at the injury to plug the leak, so the body does not lose too much blood.

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  21. Which tissue carries food made in the leaves to other parts of a plant?

    1. (A) Phloem
    2. (B) Xylem
    3. (C) Stomata
    4. (D) Root hairs
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    Correct answer: (A) Phloem

    Explanation: Phloem carries the food made in the leaves to the rest of the plant. This is called translocation, and it uses energy from ATP. Xylem carries water and minerals.

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  22. Water leaving the leaves as vapour helps pull water up from the roots. What is this process called?

    1. (A) Photosynthesis
    2. (B) Translocation
    3. (C) Respiration
    4. (D) Transpiration
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    Correct answer: (D) Transpiration

    Explanation: Water evaporating out through the stomata of leaves is transpiration. It creates a pull that draws water up through the xylem from the roots to the leaves.

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  23. What is the basic filtration unit of the kidney called?

    1. (A) Neuron
    2. (B) Nephron
    3. (C) Alveolus
    4. (D) Villus
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    Correct answer: (B) Nephron

    Explanation: Each kidney has about a million nephrons, which filter the blood and separate nitrogenous waste (urea) as urine.

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  24. What is the normal blood pressure of a healthy person?

    1. (A) 120/80 mm Hg
    2. (B) 80/120 mm Hg
    3. (C) 140/100 mm Hg
    4. (D) 100/60 mm Hg
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    Correct answer: (A) 120/80 mm Hg

    Explanation: Normal systolic pressure is about 120 mm Hg and diastolic pressure about 80 mm Hg. It is measured with a sphygmomanometer.

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  25. Assertion (A): In birds and mammals, oxygenated and deoxygenated blood must be kept separate. Reason (R): They need a lot of energy to maintain their body temperature, so an efficient oxygen supply is essential.

    1. (A) Both A and R are true, and R is the correct explanation of A.
    2. (B) Both A and R are true, but R is not the correct explanation of A.
    3. (C) A is true, but R is false.
    4. (D) A is false, but R is true.
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    Correct answer: (A) Both A and R are true, and R is the correct explanation of A.

    Explanation: A four-chambered heart and double circulation keep the two kinds of blood from mixing, so the body gets plenty of oxygen. R correctly explains A.

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