📘 Life Processes – MCQs (Class 10 Science)

🔹 Part 4: Questions 76–100

Q76. Which part of the human digestive system absorbs water?

A) Stomach
B) Small intestine
C) Large intestine
D) Liver

Correct Answer: C) Large intestine

Explanation:

• A) Stomach → Digestion only.
• B) Small intestine → Absorbs digested food.
• ✅ C) Large intestine → Absorbs excess water and salts.
• D) Liver → Produces bile, no absorption.

Q77. Which part of nephron is responsible for reabsorption of glucose?

A) Bowman’s capsule
B) Proximal tubule
C) Loop of Henle
D) Collecting duct

Correct Answer: B) Proximal tubule

Explanation:

• A) Bowman’s capsule → Filtration.
• ✅ B) PCT → Reabsorbs glucose, amino acids, ions.
• C) Loop of Henle → Reabsorbs water.
• D) Collecting duct → Collects urine.

Q78. The breakdown of glucose in the presence of oxygen is called:

A) Fermentation
B) Anaerobic respiration
C) Aerobic respiration
D) Photosynthesis

Correct Answer: C) Aerobic respiration

Explanation:

• A) Fermentation → Anaerobic in yeast.
• B) Anaerobic → Without oxygen.
• ✅ C) Aerobic respiration → With oxygen, maximum energy.
• D) Photosynthesis → Energy capture, not breakdown.

Q79. Which vein carries oxygenated blood?

A) Pulmonary vein
B) Pulmonary artery
C) Vena cava
D) Renal vein

Correct Answer: A) Pulmonary vein

Explanation:

• ✅ A) Pulmonary vein → Brings oxygenated blood from lungs.
• B) Pulmonary artery → Carries deoxygenated blood.
• C) Vena cava → Deoxygenated blood to heart.
• D) Renal vein → Filtered blood from kidneys.

Q80. What is the site of exchange of materials between blood and tissues?

A) Arteries
B) Veins
C) Capillaries
D) Venules

Correct Answer: C) Capillaries

Explanation:

• A, B → Transport only.
• ✅ C) Capillaries → Thin walls, exchange of gases & nutrients.
• D) Venules → Collect blood, no exchange.

Q81. In plants, water is transported through:

A) Phloem
B) Xylem
C) Guard cells
D) Villi

Correct Answer: B) Xylem

Explanation:

• A) Phloem → Food transport.
• ✅ B) Xylem → Water and minerals.
• C) Guard cells → Control stomata.
• D) Villi → Animal intestine.

Q82. Which enzyme digests fats?

A) Amylase
B) Pepsin
C) Lipase
D) Trypsin

Correct Answer: C) Lipase

Explanation:

• A) Amylase → Starch digestion.
• B) Pepsin → Proteins in stomach.
• ✅ C) Lipase → Breaks fats into fatty acids & glycerol.
• D) Trypsin → Proteins in small intestine.

Q83. The opening and closing of stomata depend on:

A) CO₂ concentration
B) Water content of guard cells
C) Sunlight only
D) Wind speed

Correct Answer: B) Water content of guard cells

Explanation:

• A) CO₂ → Regulates but not direct.
• ✅ B) Guard cells become turgid/flaccid → control stomata.
• C) Sunlight → Stimulates, but water is direct cause.
• D) Wind → Affects transpiration, not stomata.

Q84. In human respiration, glucose is first broken down in:

A) Mitochondria
B) Cytoplasm
C) Ribosome
D) Nucleus

Correct Answer: B) Cytoplasm

Explanation:

• ✅ B) Cytoplasm → Glycolysis (glucose → pyruvate).
• A) Mitochondria → Krebs cycle after glycolysis.
• C, D → Not sites of respiration.

Q85. In human heart, which valve prevents backflow of blood into left atrium?

A) Tricuspid valve
B) Bicuspid (mitral) valve
C) Pulmonary valve
D) Aortic valve

Correct Answer: B) Bicuspid (mitral) valve

Explanation:

• A) Tricuspid → Between right atrium & ventricle.
• ✅ B) Bicuspid → Between left atrium & ventricle.
• C) Pulmonary → At pulmonary artery.
• D) Aortic → At aorta.

Q86. Which waste product is removed through skin?

A) Urea only
B) CO₂
C) Sweat (water + salts + urea)
D) Nitrogen gas

Correct Answer: C) Sweat (water + salts + urea)

Explanation:

• A) Urea → Majorly by kidney, small amount in sweat.
• B) CO₂ → Exhaled by lungs.
• ✅ C) Sweat → Contains water, salts, little urea.
• D) Nitrogen → Not excreted this way.

Q87. Which process in plants helps in upward movement of water?

A) Photosynthesis
B) Transpiration pull
C) Respiration
D) Translocation

Correct Answer: B) Transpiration pull

Explanation:

• A) Photosynthesis → Food synthesis.
• ✅ B) Transpiration pull → Main force for ascent of sap.
• C) Respiration → Energy release.
• D) Translocation → Food transport.

Q88. Which blood vessels have valves?

A) Arteries
B) Veins
C) Capillaries
D) Arterioles

Correct Answer: B) Veins

Explanation:

• A) Arteries → Thick walls, no valves.
• ✅ B) Veins → Valves prevent backflow.
• C) Capillaries → No valves, thin walls.
• D) Arterioles → Small arteries.

Q89. The site of urea formation in humans is:

A) Kidney
B) Liver
C) Intestine
D) Skin

Correct Answer: B) Liver

Explanation:

• A) Kidney → Excretes urea.
• ✅ B) Liver → Forms urea from ammonia.
• C) Intestine → Digestion, not urea.
• D) Skin → Excretes sweat.

Q90. In which form is glucose stored in animals?

A) Starch
B) Cellulose
C) Glycogen
D) Fat

Correct Answer: C) Glycogen

Explanation:

• A) Starch → Storage in plants.
• B) Cellulose → Structural in plants.
• ✅ C) Glycogen → Storage in liver and muscles of animals.
• D) Fat → Long-term storage.

Q91. Which process produces maximum energy?

A) Anaerobic respiration
B) Aerobic respiration
C) Fermentation
D) Photosynthesis

Correct Answer: B) Aerobic respiration

Explanation:

• A) Anaerobic → Produces less energy.
• ✅ B) Aerobic → Full oxidation, maximum ATP.
• C) Fermentation → Very little energy.
• D) Photosynthesis → Stores energy, doesn’t release ATP directly.

Q92. In plants, the transport of food is:

A) Unidirectional
B) Bidirectional
C) Random
D) Downward only

Correct Answer: B) Bidirectional

Explanation:

• A) Unidirectional → Water in xylem, not food.
• ✅ B) Bidirectional → Food moves up or down as needed.
• C, D → Incorrect.

Q93. Which pigment is essential for photosynthesis?

A) Carotene
B) Xanthophyll
C) Chlorophyll
D) Anthocyanin

Correct Answer: C) Chlorophyll

Explanation:

• A & B → Accessory pigments.
• ✅ C) Chlorophyll → Main pigment for light absorption.
• D) Anthocyanin → For color, not photosynthesis.

Q94. What is the respiratory unit of lungs?

A) Bronchi
B) Bronchioles
C) Alveoli
D) Trachea

Correct Answer: C) Alveoli

Explanation:

• A) Bronchi → Air passage.
• B) Bronchioles → Smaller air tubes.
• ✅ C) Alveoli → Site of gaseous exchange.
• D) Trachea → Main windpipe.

Q95. Which blood vessel carries blood from intestine to liver?

A) Hepatic artery
B) Hepatic portal vein
C) Renal vein
D) Vena cava

Correct Answer: B) Hepatic portal vein

Explanation:

• A) Hepatic artery → Brings oxygen to liver.
• ✅ B) Hepatic portal vein → Brings nutrient-rich blood from intestine.
• C) Renal vein → From kidney.
• D) Vena cava → To heart.

Q96. What is the primary site of photosynthesis in plants?

A) Root
B) Leaf
C) Stem
D) Flower

Correct Answer: B) Leaf

Explanation:

• A) Roots → Absorb water.
• ✅ B) Leaves → Contain chloroplasts, main site.
• C) Stems → Support, limited photosynthesis in some.
• D) Flowers → Reproduction.

Q97. In human beings, fats are digested by enzymes secreted from:

A) Liver
B) Pancreas
C) Stomach
D) Large intestine

Correct Answer: B) Pancreas

Explanation:

• A) Liver → Produces bile, not enzymes.
• ✅ B) Pancreas → Secretes lipase, digests fats.
• C) Stomach → Proteins digested.
• D) Large intestine → No digestion.

Q98. Which plant structure transports prepared food?

A) Xylem
B) Phloem
C) Stomata
D) Guard cells

Correct Answer: B) Phloem

Explanation:

• A) Xylem → Water transport.
• ✅ B) Phloem → Food transport.
• C, D → For gas exchange, not transport.

Q99. Which process in cells directly produces ATP?

A) Photosynthesis
B) Respiration
C) Transpiration
D) Osmosis

Correct Answer: B) Respiration

Explanation:

• A) Photosynthesis → Produces glucose, not direct ATP for use.
• ✅ B) Respiration → Breaks glucose, releases ATP.
• C, D → Not ATP-producing processes.

Q100. Which of the following is the correct sequence of food digestion in human body?

A) Mouth → Esophagus → Stomach → Small intestine → Large intestine
B) Mouth → Stomach → Esophagus → Large intestine → Small intestine
C) Esophagus → Mouth → Stomach → Small intestine → Large intestine
D) Stomach → Mouth → Esophagus → Large intestine → Small intestine

Correct Answer: A) Mouth → Esophagus → Stomach → Small intestine → Large intestine

Explanation:

• ✅ A) Correct sequential path of digestion.
• B, C, D → Wrong order.

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