📘 Life Processes – MCQs (Class 10 Science)

🔹 Part 2: Questions 26–50

Q26. Which component of blood carries oxygen?

A) White blood cells
B) Plasma
C) Red blood cells
D) Platelets

Correct Answer: C) Red blood cells

Explanation:

• A) WBC → Defense, not oxygen transport.
• B) Plasma → Transports nutrients and hormones.
• ✅ C) RBC → Contains hemoglobin that binds oxygen.
• D) Platelets → Blood clotting.

Q27. Which enzyme digests proteins in the stomach?

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

Correct Answer: C) Pepsin

Explanation:

• A) Amylase → Digests starch.
• B) Lipase → Digests fats.
• ✅ C) Pepsin → Protein digestion in acidic medium of stomach.
• D) Trypsin → Digests proteins in intestine, not stomach.

Q28. Which gas is released during anaerobic respiration in yeast?

A) Oxygen
B) Carbon dioxide
C) Nitrogen
D) Hydrogen

Correct Answer: B) Carbon dioxide

Explanation:

• A) Oxygen → Consumed in aerobic respiration.
• ✅ B) CO₂ → Released along with ethanol during fermentation.
• C) Nitrogen → Not a respiration product.
• D) Hydrogen → Not released in this process.

Q29. What is the basic requirement for all life processes?

A) Food
B) Water
C) Energy
D) Oxygen

Correct Answer: C) Energy

Explanation:

• A) Food → Source of energy, not final requirement.
• B) Water → Needed but not main requirement.
• ✅ C) Energy → Required for all metabolic activities.
• D) Oxygen → Needed for aerobic respiration, but not by all organisms.

Q30. Which plant tissue transports water?

A) Xylem
B) Phloem
C) Cambium
D) Parenchyma

Correct Answer: A) Xylem

Explanation:

• ✅ A) Xylem → Transports water and minerals.
• B) Phloem → Food transport.
• C) Cambium → Meristematic tissue.
• D) Parenchyma → Storage, not transport.

Q31. Which vitamin is synthesized in the human intestine?

A) Vitamin A
B) Vitamin B12
C) Vitamin C
D) Vitamin D

Correct Answer: B) Vitamin B12

Explanation:

• A) Vitamin A → From diet.
• ✅ B) Vitamin B12 → Synthesized by intestinal bacteria.
• C) Vitamin C → From diet.
• D) Vitamin D → Produced in skin under sunlight.

Q32. Which chamber of the human heart pumps deoxygenated blood to lungs?

A) Right atrium
B) Left atrium
C) Right ventricle
D) Left ventricle

Correct Answer: C) Right ventricle

Explanation:

• A) Right atrium → Receives deoxygenated blood.
• B) Left atrium → Receives oxygenated blood.
• ✅ C) Right ventricle → Pumps deoxygenated blood to lungs.
• D) Left ventricle → Pumps oxygenated blood to body.

Q33. Which of the following is NOT a function of human liver?

A) Production of bile
B) Storage of glycogen
C) Excretion of urea
D) Detoxification

Correct Answer: C) Excretion of urea

Explanation:

• A) Bile production → Yes, by liver.
• B) Glycogen storage → Yes, by liver.
• ✅ C) Urea excretion → Done by kidneys, not liver.
• D) Detoxification → Yes, by liver.

Q34. In human beings, exchange of gases takes place in:

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

Correct Answer: B) Alveoli

Explanation:

• A) Bronchi → Carry air, no exchange.
• ✅ B) Alveoli → Thin membrane, site of exchange.
• C) Trachea → Air passage.
• D) Bronchioles → Carry air to alveoli.

Q35. In plants, opening and closing of stomata is controlled by:

A) Guard cells
B) Root hairs
C) Xylem vessels
D) Phloem

Correct Answer: A) Guard cells

Explanation:

• ✅ A) Guard cells → Control stomatal opening by changing turgidity.
• B) Root hairs → Absorption, not control.
• C) Xylem → Transport water.
• D) Phloem → Transport food.

Q36. The energy currency of the cell is:

A) Glucose
B) ATP
C) NADPH
D) Pyruvate

Correct Answer: B) ATP

Explanation:

• A) Glucose → Energy source, not currency.
• ✅ B) ATP → Universal energy currency.
• C) NADPH → Reducing power, not energy currency.
• D) Pyruvate → Intermediate product.

Q37. In amoeba, food is digested in:

A) Food vacuole
B) Cytoplasm
C) Nucleus
D) Contractile vacuole

Correct Answer: A) Food vacuole

Explanation:

• ✅ A) Food vacuole → Enzymes digest food here.
• B) Cytoplasm → Absorbs digested food, not site of digestion.
• C) Nucleus → Controls functions, not digestion.
• D) Contractile vacuole → Removes excess water.

Q38. Which of the following is NOT part of human excretory system?

A) Kidney
B) Ureter
C) Urethra
D) Gall bladder

Correct Answer: D) Gall bladder

Explanation:

• A, B, C → Parts of urinary system.
• ✅ D) Gall bladder → Stores bile, not excretory organ.

Q39. Which of the following carries oxygen-poor blood?

A) Pulmonary vein
B) Aorta
C) Pulmonary artery
D) Carotid artery

Correct Answer: C) Pulmonary artery

Explanation:

• A) Pulmonary vein → Oxygen-rich blood.
• B) Aorta → Oxygen-rich blood.
• ✅ C) Pulmonary artery → Carries deoxygenated blood to lungs.
• D) Carotid artery → Oxygenated blood to brain.

Q40. Insects respire through:

A) Gills
B) Lungs
C) Tracheae
D) Skin

Correct Answer: C) Tracheae

Explanation:

• A) Gills → Aquatic animals.
• B) Lungs → Mammals, reptiles, birds.
• ✅ C) Tracheae → Network of air tubes in insects.
• D) Skin → Amphibians.

Q41. What prevents backflow of blood in veins?

A) Thick walls
B) Valves
C) Muscular pressure
D) Plasma

Correct Answer: B) Valves

Explanation:

• A) Thick walls → Found in arteries.
• ✅ B) Valves → Prevent backflow in veins.
• C) Muscles assist but don’t prevent backflow directly.
• D) Plasma → Transport medium, no role in flow.

Q42. Which process removes excess water in amoeba?

A) Respiration
B) Digestion
C) Excretion
D) Osmoregulation

Correct Answer: D) Osmoregulation

Explanation:

• A) Respiration → Energy release.
• B) Digestion → Food breakdown.
• C) Excretion → Removal of wastes like urea/CO₂.
• ✅ D) Osmoregulation → Controlled by contractile vacuole in amoeba.

Q43. In human beings, food is completely digested in:

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

Correct Answer: B) Small intestine

Explanation:

• A) Stomach → Partial digestion.
• ✅ B) Small intestine → Enzymes from pancreas and bile complete digestion.
• C) Large intestine → Absorbs water, not food.
• D) Esophagus → Only transports food.

Q44. Which of the following organisms respires anaerobically?

A) Man
B) Yeast
C) Amoeba
D) Fish

Correct Answer: B) Yeast

Explanation:

• A) Man → Aerobic respiration.
• ✅ B) Yeast → Anaerobic respiration (fermentation).
• C) Amoeba → Aerobic respiration.
• D) Fish → Aerobic (gills).

Q45. During respiration, glucose is first broken into:

A) Pyruvate
B) Ethanol
C) Lactic acid
D) Acetyl-CoA

Correct Answer: A) Pyruvate

Explanation:

• ✅ A) Pyruvate → End product of glycolysis.
• B) Ethanol → Produced in yeast (anaerobic).
• C) Lactic acid → Produced in muscles during anaerobic respiration.
• D) Acetyl-CoA → Formed from pyruvate in mitochondria.

Q46. In which organ does absorption of digested food take place?

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

Correct Answer: B) Small intestine

Explanation:

• A) Stomach → Digestion only.
• ✅ B) Small intestine → Villi absorb nutrients.
• C) Large intestine → Absorbs water.
• D) Liver → Stores and processes food, not absorption.

Q47. Which process in plants is important for ascent of sap?

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

Correct Answer: B) Transpiration

Explanation:

• A) Photosynthesis → Food production.
• ✅ B) Transpiration → Creates suction pull for water movement.
• C) Respiration → Energy production.
• D) Translocation → Food transport, not water.

Q48. Which of the following is the first step in nutrition?

A) Absorption
B) Assimilation
C) Ingestion
D) Digestion

Correct Answer: C) Ingestion

Explanation:

• ✅ C) Ingestion → Intake of food.
• A) Absorption → After digestion.
• B) Assimilation → Use of absorbed food.
• D) Digestion → After ingestion.

Q49. The exchange of gases in humans occurs by:

A) Active transport
B) Osmosis
C) Diffusion
D) Endocytosis

Correct Answer: C) Diffusion

Explanation:

• A) Active transport → Requires energy, not in gas exchange.
• B) Osmosis → Only for water.
• ✅ C) Diffusion → O₂ and CO₂ exchange across alveoli.
• D) Endocytosis → Cell engulfing, not gases.

Q50. Which part of the nephron is responsible for concentration of urine?

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

Correct Answer: B) Loop of Henle

Explanation:

• A) Bowman’s capsule → Filtration.
• ✅ B) Loop of Henle → Reabsorbs water, concentrates urine.
• C) PCT → Absorbs nutrients.
• D) Collecting duct → Final urine passage.

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