Life Processes – MCQs with Answers and Explanations
Class 10
Biology — Chapter 5: Life Processes — 50 MCQs
NCERT-aligned topic-wise multiple choice questions with answers and clear explanations for CBSE Class 10.
CBSE Board Examinations — Systematic Order Provided
Practice these MCQs to strengthen concepts and exam readiness.
Content Bank — Topics covered
- Nutrition (photosynthesis, types of nutrition)
- Digestion and enzymes
- Respiration (aerobic & anaerobic)
- Transport (xylem, phloem, blood, heart)
- Excretion (kidney, nephron)
- Breathing & gas exchange, transpiration, stomata
- Soaps, detergents, plant adaptations and hormones
Systematic order for practice:
- Nutrition (Q1–Q8)
- Digestion & Enzymes (Q9–Q16)
- Respiration (Q17–Q24)
- Transport in Plants & Animals (Q25–Q34)
- Excretion (Q35–Q40)
- Breathing, Gas Exchange & Transpiration (Q41–Q47)
- Applications & Miscellaneous (Q48–Q50)
Q1.
Which of the following is NOT required for photosynthesis?
Correct: C. Oxygen
Explanation: Photosynthesis produces oxygen as a by-product; CO₂, chlorophyll and sunlight are required to synthesise glucose.
Q2.
The primary site of photosynthesis in a leaf is:
Correct: C. Palisade mesophyll
Explanation: Palisade mesophyll cells contain many chloroplasts and are the main photosynthetic tissue in leaves.
Q3.
Which gas is taken up during photosynthesis and released during respiration?
Correct: B. Carbon dioxide
Explanation: Plants take in CO₂ for photosynthesis; during cellular respiration organisms release CO₂ as a waste product.
Q4.
Which of the following statements about stomata is true?
Correct: A. They are involved in transpiration and gas exchange.
Explanation: Stomata open and close, controlled by guard cells, allowing gas exchange and regulating water loss (transpiration). They are usually on leaf underside.
Q5.
Which molecule captures light energy in photosynthesis?
Correct: B. Chlorophyll
Explanation: Chlorophyll is the pigment in chloroplasts that absorbs light energy for the light-dependent reactions.
Q6.
Which of the following is a product of photosynthesis?
Correct: B. Oxygen
Explanation: Photosynthesis produces glucose and oxygen; oxygen is released into the atmosphere.
Q7.
A plant kept in darkness for several days will show which of the following?
Correct: B. Decreased chlorophyll and etiolated appearance
Explanation: Lack of light reduces chlorophyll production and photosynthesis; plants become pale and elongated (etiolation) as they seek light.
Q8.
Which factor does NOT increase the rate of photosynthesis beyond a certain limit?
Correct: C. Temperature (beyond optimum)
Explanation: While temperature increases photosynthesis up to an optimum, beyond that enzymes denature and the rate falls.
Q9.
Which enzyme begins the digestion of starch in the mouth?
Correct: B. Salivary amylase (ptyalin)
Explanation: Salivary amylase starts breaking down starch to maltose in the mouth; pepsin acts on proteins in stomach.
Q10.
Where are most nutrients absorbed in the human digestive system?
Correct: C. Small intestine (ileum)
Explanation: The small intestine, especially the ileum with villi and microvilli, is the main site for nutrient absorption.
Q11.
Which organ secretes bile and what is its role in digestion?
Correct: B. Liver; emulsifies fats
Explanation: Liver produces bile to emulsify fats (mechanical breakdown), stored in gall bladder; pancreas secretes digestive enzymes.
Q12.
Which enzyme is important for protein digestion in the stomach?
Correct: C. Pepsin
Explanation: Pepsin works in the acidic environment of stomach to break proteins into peptides; trypsin acts in small intestine.
Q13.
Which structure increases surface area of the small intestine for absorption?
Correct: A. Villi and microvilli
Explanation: Villi and microvilli increase the absorptive surface area in the small intestine for efficient nutrient uptake.
Q14.
Pancreatic juice contains which of the following?
Correct: B. Digestive enzymes like trypsin, lipase and amylase
Explanation: Pancreatic juice contains digestive enzymes; bile salts are from liver; insulin is a hormone from pancreas (endocrine function).
Q15.
Which of these is NOT an absorbable unit of food?
Correct: D. Starch
Explanation: Starch is a complex carbohydrate that must be broken down into monosaccharides (glucose) before absorption.
Q16.
Which secretions neutralise acidic chyme entering the small intestine from stomach?
Correct: C. Pancreatic secretions
Explanation: Pancreatic juice is alkaline (contains bicarbonate) and neutralises acidic chyme, creating suitable pH for intestinal enzymes.
Q17.
Which of the following is the end product of aerobic respiration?
Correct: C. CO₂ and H₂O
Explanation: Aerobic respiration completely oxidises glucose to CO₂ and H₂O with a high yield of ATP.
Q18.
Glycolysis occurs in which part of the cell?
Correct: B. Cytoplasm
Explanation: Glycolysis is the initial breakdown of glucose into pyruvate and occurs in the cytosol of cells.
Q19.
Which organism performs alcoholic fermentation?
Correct: B. Yeast
Explanation: Yeast ferments glucose anaerobically to ethanol and CO₂, used in baking and brewing.
Q20.
Lactic acid in muscles is produced when:
Correct: B. Oxygen is deficient during strenuous exercise
Explanation: Under low O₂, muscle cells switch to anaerobic respiration producing lactic acid, causing temporary muscle fatigue.
Q21.
Which process produces maximum ATP from glucose?
Correct: C. Aerobic respiration (oxidative phosphorylation)
Explanation: Oxidative phosphorylation in mitochondria produces the most ATP per glucose molecule compared to glycolysis or fermentation.
Q22.
Which organelle is known as the powerhouse of the cell?
Correct: C. Mitochondrion
Explanation: Mitochondria are the sites of Krebs cycle and oxidative phosphorylation producing ATP during aerobic respiration.
Q23.
Which of the following is TRUE about anaerobic respiration?
Correct: C. It produces incomplete oxidation products like lactic acid or ethanol
Explanation: Anaerobic respiration yields less ATP and produces lactic acid (animals) or ethanol + CO₂ (yeast) without requiring oxygen.
Q24.
During respiration, which molecule acts as the final electron acceptor at the end of electron transport chain?
Correct: B. Oxygen
Explanation: Oxygen accepts electrons to form water at the end of the electron transport chain in aerobic respiration.
Q25.
Xylem primarily transports:
Correct: B. Water and minerals
Explanation: Xylem vessels conduct water and dissolved minerals upward from roots to shoots; phloem transports sugars.
Q26.
Phloem translocation is best explained by which hypothesis?
Correct: B. Pressure-flow (mass flow) hypothesis
Explanation: Sugars are actively loaded into phloem at source, drawing water in and generating pressure that pushes sap toward sinks where sugars are unloaded.
Q27.
Which blood cells are primarily responsible for oxygen transport?
Correct: C. Red blood cells (RBCs)
Explanation: RBCs contain haemoglobin which binds and transports oxygen to tissues.
Q28.
Which component of blood helps in clotting?
Correct: C. Platelets
Explanation: Platelets and clotting factors in plasma form a plug to prevent blood loss and initiate clot formation.
Q29.
Double circulation refers to:
Correct: B. Blood passing through the heart twice in one circuit
Explanation: In double circulation (as in humans), blood goes through pulmonary circuit (heart to lungs and back) and systemic circuit (heart to body and back), passing the heart twice per cycle.
Q30.
Which structure prevents backflow of blood from ventricles to atria?
Correct: B. Atrioventricular valves (tricuspid & mitral)
Explanation: AV valves between atria and ventricles prevent backflow during ventricular contraction; semilunar valves prevent backflow from arteries into ventricles.
Q31.
Which of the following is a plasma component?
Correct: C. Urea and dissolved nutrients
Explanation: Plasma is the liquid part of blood carrying dissolved substances like nutrients, hormones and waste such as urea.
Q32.
Which tissue conducts water upwards in plants?
Correct: B. Xylem
Explanation: Xylem vessels and tracheids conduct water and dissolved minerals from roots to aerial parts.
Q33.
Sieve tubes are associated with which cells for functioning?
Correct: A. Companion cells
Explanation: Sieve tube elements lack nucleus and rely on companion cells for metabolic support and loading/unloading of sugars.
Q34.
Which term describes the watery fluid that bathes body cells and is returned to blood via lymphatics?
Correct: C. Tissue fluid
Explanation: Tissue fluid surrounds cells; lymph is the collected excess tissue fluid transported by lymphatic vessels back to the blood.
Q35.
The functional unit of the kidney is:
Correct: B. Nephron
Explanation: Nephron (glomerulus + renal tubule) performs filtration, reabsorption and secretion to form urine.
Q36.
Filtration in the kidney occurs at:
Correct: B. Bowman’s capsule (glomerulus)
Explanation: Blood is filtered at glomerulus into Bowman’s capsule producing primary filtrate free of large proteins and cells.
Q37.
Which hormone increases water reabsorption in kidney collecting ducts?
Correct: C. ADH (antidiuretic hormone)
Explanation: ADH from posterior pituitary increases permeability of collecting ducts to water, concentrating urine when body needs to conserve water.
Q38.
Which substance is normally not present in urine in significant amounts?
Correct: B. Glucose
Explanation: Glucose is normally reabsorbed in renal tubules; its presence (glycosuria) indicates high blood glucose exceeding renal threshold (e.g., diabetes).
Q39.
Selective reabsorption mainly occurs in which part of nephron?
Correct: B. Proximal convoluted tubule (PCT)
Explanation: PCT performs significant reabsorption of glucose, amino acids, salts and water via active and passive transport mechanisms.
Q40.
Which of these is a function of the kidney besides excretion?
Correct: B. Regulation of blood volume and pressure
Explanation: Kidneys regulate blood volume and pressure via water/salt balance and renin release; they also help maintain acid-base balance.
Q41.
Gas exchange in human lungs occurs at:
Correct: C. Alveoli
Explanation: Alveoli provide large surface area, thin walls, and capillary networks for efficient diffusion of O₂ and CO₂.
Q42.
What causes inhalation?
Correct: B. Diaphragm contraction and lowered thoracic pressure
Explanation: Diaphragm contracts (flattens), chest cavity volume increases, intrapulmonary pressure falls and air flows into lungs.
Q43.
Which feature of alveoli helps prevent collapse and reduce surface tension?
Correct: B. Surfactant
Explanation: Pulmonary surfactant reduces surface tension in alveoli, preventing collapse and aiding lung compliance.
Q44.
Transpiration in plants primarily helps in:
Correct: B. Uptake and upward movement of water and minerals
Explanation: Transpiration creates a transpiration pull that helps draw water up through xylem from roots to leaves, assisting mineral transport.
Q45.
Which cells control stomatal opening and closing?
Correct: C. Guard cells
Explanation: Guard cells change turgor (by K+ and water movement) to open or close stomatal pore regulating gas exchange and transpiration.
Q46.
Which factor would decrease transpiration rate?
Correct: C. Darkness (stomata closed)
Explanation: In darkness many plants close stomata, reducing transpiration; other factors like wind, low humidity and high temperature increase transpiration.
Q47.
Which statement is true about exchange surfaces?
Correct: B. They have large surface area and thin walls
Explanation: Efficient exchange surfaces like alveoli and villi are thin and have large surface areas and rich blood supply to facilitate diffusion.
Q48.
Which of the following is TRUE about detergents compared to soaps?
Correct: C. Detergents do not form scum with hard water salts
Explanation: Detergents contain sulphonate groups that remain soluble in hard water, whereas soap anions form insoluble salts (scum) with Ca²⁺/Mg²⁺.
Q49.
Which adaptation helps xerophytic plants reduce water loss?
Correct: B. Sunken stomata and thick cuticle
Explanation: Xerophytes reduce water loss via thick cuticle, sunken stomata, reduced leaf area (spines), and other features adapted for arid conditions.
Q50.
Which statement best describes homeostasis?
Correct: B. Maintenance of a stable internal environment despite external changes
Explanation: Homeostasis involves regulation of internal parameters (temperature, pH, water balance) to keep conditions within narrow limits for proper functioning.