Nutrition — Short Questions (1–10)

1. 1. What is photosynthesis?
   Process by which green plants synthesise glucose and oxygen from carbon dioxide and water using sunlight and chlorophyll.
2. 2. Name the organelle where photosynthesis occurs.
   Chloroplast (contains chlorophyll; present in leaf mesophyll cells).
3. 3. Write the balanced chemical equation for photosynthesis.
   6 CO₂ + 6 H₂O —(light, chlorophyll)→ C₆H₁₂O₆ + 6 O₂.
4. 4. What are light and dark reactions in photosynthesis?
   Light reactions capture light energy to form ATP and NADPH; dark reactions (Calvin cycle) use ATP/NADPH to fix CO₂ into glucose.
5. 5. Define autotrophic nutrition.
   Mode of nutrition where organisms produce their own food from inorganic substances (example: green plants).
6. 6. Define heterotrophic nutrition.
   Obtaining food by consuming other organisms or organic material (animals, fungi, many bacteria).
7. 7. What is holozoic nutrition?
   Type of heterotrophic nutrition involving ingestion, digestion, absorption and assimilation, typical of animals.
8. 8. What is saprophytic nutrition?
   Nutrition where organisms (e.g., fungi) secrete enzymes to digest dead material externally and absorb nutrients.
9. 9. Give two factors affecting photosynthesis.
   Light intensity, CO₂ concentration, temperature, and chlorophyll content (any two).
10. 10. What are stomata and their function?
    Pores on leaf surfaces controlled by guard cells; allow gas exchange (CO₂ in, O₂ out) and regulate transpiration.

Digestion & Related (11–20)

1. 11. Name the main regions of the human alimentary canal.
   Mouth, pharynx, oesophagus, stomach, small intestine, large intestine, rectum, anus.
2. 12. What enzyme starts digestion of starch in the mouth?
   Salivary amylase (ptyalin) begins starch breakdown into maltose.
3. 13. Where does most absorption of nutrients occur?
   Small intestine (especially the ileum) — villi increase surface area for absorption.
4. 14. What is the role of the liver in digestion?
   Produces bile which emulsifies fats and aids fat digestion; also detoxifies and stores glycogen.
5. 15. What does pancreatic juice contain?
   Enzymes like amylase (for starch), proteases (for proteins), and lipase (for fats); also alkaline to neutralize chyme.
6. 16. Define assimilation.
   Conversion of absorbed nutrients into living tissues or used as energy — incorporation into cells.
7. 17. What is egestion?
   Removal of undigested waste from the digestive tract (faeces) via the anus.
8. 18. Name a proteolytic enzyme and where it acts.
   Pepsin in the stomach (acts in acidic medium) and trypsin in the small intestine (acts in alkaline medium).
9. 19. What structural feature of small intestine helps absorption?
   Villi and microvilli provide large surface area and contain blood capillaries and lacteals for nutrient transport.
10. 20. Why is stomach acid important?
    Hydrochloric acid provides acidic pH for pepsin activity and kills many microbes in food.

Respiration — Short Questions (21–30)

1. 21. Define respiration in living organisms.
   Process of releasing energy by oxidation of food molecules (glucose) to power cellular activities.
2. 22. What are the products of aerobic respiration?
   Carbon dioxide, water and energy (ATP).
3. 23. Where does glycolysis occur?
   In the cytoplasm of the cell — glucose is broken into pyruvate producing small ATP.
4. 24. Name the organelle where Krebs cycle takes place.
   Mitochondrial matrix (Krebs cycle occurs there).
5. 25. Give one difference between aerobic and anaerobic respiration.
   Aerobic uses oxygen and yields more ATP; anaerobic occurs without oxygen and yields less ATP (produces lactic acid or ethanol + CO₂).
6. 26. What is fermentation in yeast?
   Anaerobic conversion of glucose to ethanol and CO₂, with small ATP yield.
7. 27. Why do muscles produce lactic acid temporarily?
   Under vigorous exercise with limited O₂, muscles undergo anaerobic respiration producing lactic acid.
8. 28. What is oxygen debt?
   Extra oxygen required after exercise to oxidise accumulated lactic acid and restore normal conditions.
9. 29. Define ATP.
   Adenosine triphosphate, the primary energy-carrying molecule used by cells.
10. 30. How is CO₂ transported in blood?
    As bicarbonate ions in plasma, dissolved CO₂, and combined with haemoglobin as carbamino compounds.

Transport (Plants & Animals) — Short Questions (31–40)

1. 31. What is transpiration pull?
   Tension created by water evaporation from leaves that helps pull water up through xylem vessels.
2. 32. Name two types of xylem elements.
   Tracheids and vessel elements (vessels) — conduct water and provide support.
3. 33. What is phloem composed of?
   Sieve tube elements, companion cells, phloem fibres and phloem parenchyma for translocation of food.
4. 34. What is the pressure-flow hypothesis?
   Explains phloem translocation where high pressure at source pushes sap to lower pressure at sink (mass flow).
5. 35. What is double circulation?
   Blood passes through heart twice in one complete cycle (pulmonary and systemic circuits) — seen in mammals.
6. 36. List major components of blood.
   Plasma, red blood cells (RBCs), white blood cells (WBCs) and platelets.
7. 37. What is the function of RBCs?
   Carry oxygen to tissues using haemoglobin and assist in CO₂ transport.
8. 38. What role do white blood cells play?
   Defend the body against infections (phagocytosis, antibody production by lymphocytes).
9. 39. What is the role of platelets?
   Aid in blood clotting by forming a plug and releasing clotting factors.
10. 40. What is coronary circulation?
    Blood supply to the heart muscle via coronary arteries and removal via cardiac veins.

Excretion & Breathing — Short Questions (41–50)

1. 41. What is the basic functional unit of the kidney?
   Nephron (glomerulus + renal tubule) — filters blood and forms urine.
2. 42. What is glomerular filtration?
   Filtration of blood plasma through glomerular capillaries into Bowman’s capsule, forming filtrate.
3. 43. Name two processes involved in urine formation.
   Filtration, selective reabsorption and secretion (three key processes; two may be named).
4. 44. How does ADH affect urine concentration?
   ADH increases water reabsorption in collecting ducts, producing more concentrated urine.
5. 45. What is the role of alveoli in lungs?
   Sites of gas exchange where O₂ diffuses into blood and CO₂ diffuses out into alveolar air.
6. 46. Explain inhalation in one line.
   Diaphragm contracts and moves downward, ribs move up and out, chest volume increases drawing air in.
7. 47. Explain exhalation in one line.
   Diaphragm relaxes, ribs move down, chest volume decreases, and air is expelled from the lungs.
8. 48. How is oxygen exchanged at the tissue level?
   Oxygen unloads from haemoglobin and diffuses into cells where it is used in cellular respiration.
9. 49. What causes increased breathing rate during exercise?
   Rise in CO₂ and demand for O₂ by muscles stimulates respiratory center to increase breathing rate and depth.
10. 50. State one function of the skin related to excretion.
    Perspiration via sweat glands helps remove small amounts of salts, water and some nitrogenous wastes and cools the body.

Study tip: Convert each short answer into one sentence in your own words and practise writing them quickly — excellent for scoring in board exams.