Answers are written in an exam-focused, easy-to-read style with bullet points and labelled steps where needed.

1. Question 1: Explain in detail the process of photosynthesis. Include the main stages, site of reactions and the overall equation.

   Answer:

   • Definition: Photosynthesis is the process by which green plants synthesize carbohydrates (glucose) from carbon dioxide and water using light energy trapped by chlorophyll.
   • Overall equation: 6 CO₂ + 6 H₂O —(light, chlorophyll)→ C₆H₁₂O₆ + 6 O₂.
   • Site: Occurs in chloroplasts — primarily in palisade mesophyll cells of leaves.
   • Two main stages:
     • Light reactions (thylakoid membranes): Light energy splits water (photolysis), produces O₂, ATP and NADPH.
     • Dark reactions / Calvin cycle (stroma): ATP and NADPH are used to fix CO₂ into 3‑carbon compounds and eventually form glucose.
   • Factors affecting photosynthesis: Light intensity, CO₂ concentration, temperature, chlorophyll amount.
   • Exam tip: Mention sites (thylakoid for light reactions and stroma for Calvin cycle) and write the balanced equation to secure full marks.
2. Question 2: Describe the structure of a chloroplast and explain how its structure is related to its function in photosynthesis.

   Answer:

   • Key structures: Double membrane envelope, stroma (fluid), thylakoid membranes stacked as grana, thylakoid lumen, chlorophyll pigment embedded in thylakoid membranes.
   • Function relation:
     • Thylakoid membranes provide large surface area for light reactions where chlorophyll and electron carriers are located.
     • Grana stacks ensure efficient light capture and separation of photochemical reactions.
     • Stroma contains enzymes for the Calvin cycle (carbon fixation) where ATP and NADPH are used to synthesise sugars.
   • Exam tip: A labelled sketch with thylakoids/grana and stroma and short notes linking structure to stages earns good marks.
3. Question 3: Explain the differences between autotrophic and heterotrophic nutrition with examples.

   Answer:

   • Autotrophic nutrition:
     • Organisms synthesize their own food from inorganic materials (CO₂ and H₂O) using sunlight (photosynthesis) or chemical energy (chemosynthesis).
     • Example: Green plants, algae (photosynthetic autotrophs).
     • Key point: Self-sustaining, primary producers in food chains.
   • Heterotrophic nutrition:
     • Organisms obtain food by consuming other organisms or organic matter.
     • Types: Holozoic (animal ingestion and digestion), saprophytic (external digestion of dead matter by fungi), parasitic (derive from host).
     • Examples: Humans (holozoic), fungi like Rhizopus (saprophytic), Plasmodium (parasitic).
   • Exam tip: Use a table to show differences — source of food, method, examples and ecological role.
4. Question 4: Describe the human digestive system and explain the role of liver and pancreas in digestion.

   Answer:

   • Major parts: Mouth (saliva, chewing), pharynx, oesophagus (peristalsis), stomach (acidic digestion with pepsin), small intestine (duodenum, jejunum, ileum — majority of digestion and absorption), large intestine (water absorption), rectum and anus (egestion).
   • Liver: Produces bile which emulsifies fats (increases surface area for lipase action); also detoxifies substances and stores glycogen.
   • Pancreas: Produces pancreatic juice containing enzymes — amylase (starch), proteases (trypsin, chymotrypsin for proteins), lipase (fats); secretes alkaline fluid to neutralise chyme.
   • Absorption: Nutrients absorbed in small intestine via villi — glucose and amino acids into blood capillaries; fatty acids & glycerol into lacteals (lymph).
   • Exam tip: Labelled diagram of alimentary canal with brief function notes is essential.
5. Question 5: Explain the process of digestion of carbohydrates, proteins and fats in the human digestive tract.

   Answer:

   • Carbohydrates:
     • Starts in mouth: salivary amylase breaks starch into maltose.
     • Continues in small intestine: pancreatic amylase converts remaining starch to disaccharides; brush border enzymes (maltase, sucrase, lactase) convert disaccharides to monosaccharides (glucose).
   • Proteins:
     • Begins in stomach: pepsin (acidic) hydrolyses proteins to peptides.
     • In small intestine: pancreatic proteases (trypsin, chymotrypsin) act on peptides; peptidases on brush border produce amino acids which are absorbed.
   • Fats (lipids):
     • Emulsified by bile salts from liver (mechanical process) increasing surface area.
     • Pancreatic lipase hydrolyses triglycerides to fatty acids and monoglycerides which are absorbed into lacteals after reformation as chylomicrons.
   • Exam tip: Mention enzymes and sites (mouth, stomach, small intestine) and final absorbable units (glucose, amino acids, fatty acids + glycerol).
6. Question 6: Define respiration. Describe aerobic respiration with steps and mention where each step occurs in the cell.

   Answer:

   • Definition: Respiration is the biochemical process of releasing energy by oxidation of food molecules (mainly glucose).
   • Aerobic respiration overall: C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + energy (ATP).
   • Steps & sites:
     • Glycolysis (cytosol): glucose → 2 pyruvate + small ATP + NADH.
     • Pyruvate oxidation and Krebs cycle (mitochondrial matrix): pyruvate → acetyl-CoA → CO₂ + NADH + FADH₂; small ATP formed.
     • Electron Transport Chain (inner mitochondrial membrane): NADH and FADH₂ donate electrons; proton gradient drives ATP synthase producing large ATP; O₂ is final electron acceptor forming H₂O.
   • Energy yield note: Aerobic respiration yields far more ATP per glucose than anaerobic pathways.
   • Exam tip: Write stages and sites clearly and note that mitochondria are the powerhouse for aerobic respiration.
7. Question 7: Compare aerobic and anaerobic respiration. Give examples where anaerobic respiration occurs and its products.

   Answer:

   • Aerobic respiration: Occurs in presence of oxygen, yields CO₂, H₂O and large amount of ATP; site mainly mitochondria.
   • Anaerobic respiration: Occurs without oxygen, yields less ATP and different end products depending on organism; occurs in cytosol.
   • Examples & products:
     • In yeast (fermentation): Glucose → ethanol + CO₂ + small ATP (used in brewing and baking).
     • In animal muscle under low oxygen: Glucose → lactic acid + small ATP (causes temporary muscle fatigue).
   • Exam tip: Provide comparative table: oxygen requirement, ATP yield, end products, location, examples.
8. Question 8: Explain the structure of the human heart and describe the flow of blood through the heart including the role of valves.

   Answer:

   • Heart structure: Four-chambered muscular organ — two atria (upper chambers) and two ventricles (lower chambers); right and left sides separated by septum; valves: tricuspid (between right atrium & ventricle), pulmonary (right ventricle to pulmonary artery), mitral/bicuspid (left atrium to left ventricle), aortic (left ventricle to aorta).
   • Blood flow:
     1. Deoxygenated blood from body → superior/inferior vena cava → right atrium → through tricuspid valve → right ventricle.
     2. Right ventricle pumps blood through pulmonary valve → pulmonary artery → lungs (oxygenation).
     3. Oxygenated blood from lungs → pulmonary veins → left atrium → through mitral valve → left ventricle.
     4. Left ventricle pumps blood through aortic valve → aorta → systemic circulation to body tissues.
   • Role of valves: Prevent backflow, ensure unidirectional flow; open/close in response to pressure differences.
   • Exam tip: Clear labelled diagram of the heart with arrows for flow and mention double circulation (pulmonary & systemic).
9. Question 9: Describe the composition and functions of blood.

   Answer:

   • Components: Plasma (liquid 55%) and formed elements (45%): red blood cells (RBCs/erythrocytes), white blood cells (WBCs/leukocytes), platelets.
   • Functions:
     • RBCs carry oxygen using haemoglobin and help in CO₂ transport.
     • WBCs defend against infection (phagocytosis by neutrophils; antibody production by lymphocytes).
     • Platelets help in blood clotting to prevent blood loss.
     • Plasma transports nutrients, hormones, wastes (urea), and maintains osmotic balance.
   • Exam tip: Mention normal haemoglobin role and that RBCs lack nucleus in mammals (adaptation for packing more haemoglobin).
10. Question 10: Explain how respiration and transport are coordinated during vigorous exercise.

    Answer:

    • During exercise: Muscle cells require more oxygen and produce more CO₂ due to increased metabolism.
    • Respiratory changes: Breathing rate and tidal volume increase to take in more O₂ and expel CO₂; deeper and faster breaths increase alveolar ventilation.
    • Circulatory changes: Heart rate and stroke volume increase, cardiac output rises to deliver more oxygenated blood to muscles; vasodilation in active muscles increases blood flow.
    • Coordination: Increased CO₂ and decreased blood pH stimulate chemoreceptors, signalling respiratory centre to increase breathing; sympathetic nervous system raises heart rate.
    • After exercise: Oxygen debt is repaid — extra oxygen used to oxidise lactic acid back to pyruvate and to restore ATP/creatine phosphate stores.
11. Question 11: Describe the process of transpiration in plants and explain three factors affecting the rate of transpiration.

    Answer:

    • Transpiration: Loss of water vapour from aerial parts of plants, mainly through stomata in leaves; creates transpiration pull that helps in upward movement of water in xylem.
    • Mechanism: Water evaporates from mesophyll cell walls into intercellular spaces and diffuses out via stomata leading to a continuous column of water maintained by cohesion and adhesion — cohesion-tension theory.
    • Factors affecting transpiration:
      • Light intensity — opens stomata increasing transpiration.
      • Temperature — higher temperature increases evaporation and diffusion rates.
      • Humidity — low atmospheric humidity increases transpiration rate; high humidity reduces it.
      • Wind — removes saturated air layer at leaf surface increasing transpiration.
    • Exam tip: Relate transpiration to xylem sap ascent and mention stomatal control via guard cells.
12. Question 12: Explain the structure and function of xylem and phloem in plants.

    Answer:

    • Xylem:
      • Composed of tracheids, vessel elements, xylem parenchyma and fibres — dead cells with thick lignified walls in mature state.
      • Function: Transport water and dissolved minerals from roots to aerial parts and provide mechanical support.
    • Phloem:
      • Composed of sieve tube elements, companion cells, phloem parenchyma and fibres — living cells (sieve tubes lack nucleus but have companion cells).
      • Function: Translocation of organic solutes (mainly sucrose) from source (leaf) to sink (roots, fruits) via pressure flow mechanism.
    • Exam tip: A neat diagram of vascular bundle and brief functions of xylem & phloem score well.
13. Question 13: Describe the mass flow hypothesis (pressure flow hypothesis) for translocation in phloem.

    Answer:

    • Concept: Sugars (primarily sucrose) are actively loaded into phloem sieve tubes at source (leaf), increasing osmotic pressure and drawing water in from xylem; this generates high turgor pressure at source.
    • Flow: Hydrostatic pressure pushes phloem sap toward sink regions (roots, fruits) where sucrose is unloaded, reducing osmotic pressure and causing water to exit back to xylem, maintaining pressure gradient.
    • Evidence: Pressure differences measured; sap flows in both directions depending on source-sink dynamics.
    • Exam tip: Explain active loading at source, passive unloading at sink and role of companion cells.
14. Question 14: Explain glomerular filtration, tubular reabsorption, and tubular secretion in the nephron and how they contribute to urine formation.

    Answer:

    • Glomerular filtration: Blood pressure forces plasma (minus large proteins and cells) through glomerular capillaries into Bowman’s capsule forming primary filtrate containing water, glucose, salts and urea.
    • Tubular reabsorption: Useful substances (glucose, amino acids, majority of water and ions) are selectively reabsorbed from renal tubules back into peritubular capillaries (mainly in proximal convoluted tubule, loop of Henle and collecting duct).
    • Tubular secretion: Additional wastes and excess ions (H⁺, K⁺, organic acids) are secreted from blood into tubule to fine-tune composition of urine (distal tubule & collecting duct).
    • Result — urine: Concentrated waste containing urea, excess salts and water collected in collecting ducts, drained to renal pelvis → ureter → bladder.
    • Exam tip: Be able to label nephron regions and summarise functions in one line each.
15. Question 15: Discuss the mechanism of breathing in humans. Include the role of diaphragm and intercostal muscles.

    Answer:

    • Inhalation (inspiration): Diaphragm contracts and flattens; external intercostal muscles contract raising ribs outward; thoracic cavity volume increases; intrapulmonary pressure falls below atmospheric pressure; air flows into lungs.
    • Exhalation (expiration): Diaphragm relaxes (becomes dome-shaped); external intercostals relax, ribs move down; thoracic volume decreases; intrapulmonary pressure rises above atmospheric pressure; air is expelled. During forceful expiration, internal intercostal & abdominal muscles contract.
    • Alveolar exchange: At alveoli, O₂ diffuses into blood and CO₂ diffuses out along concentration gradients; large surface area and thin walls facilitate diffusion.
    • Exam tip: Include diagram of lungs/chest cavity and arrowed movement for inhalation/exhalation to score diagram marks.
16. Question 16: Explain how oxygen is transported in the blood and how CO₂ is transported from tissues to lungs.

    Answer:

    • Oxygen transport: Most O₂ binds reversibly to haemoglobin in RBCs forming oxyhaemoglobin (HbO₂); small amount dissolves in plasma.
    • Factors affecting O₂ binding: Partial pressure of O₂, pH, temperature and 2,3‑BPG (Bohr effect) influence haemoglobin affinity.
    • CO₂ transport:
      • Dissolved CO₂ in plasma (small amount).
      • Combined with haemoglobin (carbaminohaemoglobin).
      • Most converted to bicarbonate ions (HCO₃⁻) in RBCs via carbonic anhydrase; HCO₃⁻ transported in plasma — reversed in lungs to release CO₂.
    • Exam tip: Mention reversible binding and role of carbonic anhydrase for full explanation.
17. Question 17: Discuss the role of enzymes in digestion and give examples of specific enzymes and their substrates.

    Answer:

    • Role: Enzymes catalyse biochemical breakdown of macromolecules into absorbable units without being consumed — speed up digestive reactions and function optimally at specific pH.
    • Examples:
      • Amylase (salivary and pancreatic) — substrate: starch → products: maltose and dextrins.
      • Pepsin (stomach) — substrate: proteins → peptides (works in acidic pH).
      • Trypsin and chymotrypsin (pancreas) — further protein hydrolysis in small intestine.
      • Lipase (pancreas) — substrate: triglycerides → fatty acids + glycerol (aided by bile salts).
    • Exam tip: Mention where each enzyme acts (mouth, stomach, small intestine) and pH preferences briefly.
18. Question 18: Explain the adaptations of the small intestine that make it efficient for absorption.

    Answer:

    • Large surface area: Long length, circular folds (plicae), villi and microvilli (brush border) increase surface area enormously.
    • Thin epithelium: Single layer of epithelial cells allows short diffusion distance for nutrients.
    • Rich blood supply & lacteals: Capillaries in villi transport absorbed amino acids and sugars; lacteals absorb fats as chylomicrons.
    • Enzymes & transporters: Brush border enzymes and specific transport proteins facilitate uptake of nutrients.
    • Exam tip: A labelled villus diagram with mention of capillaries and lacteal is useful.
19. Question 19: Describe how kidney function maintains homeostasis of the body fluids.

    Answer:

    • Filtration and selective reabsorption: Kidneys filter blood removing wastes while reabsorbing useful substances, thus maintaining composition and volume of body fluids.
    • Electrolyte balance: Kidneys regulate sodium, potassium, chloride and other ions through reabsorption and secretion maintaining osmotic balance.
    • Acid-base balance: By secreting H⁺ and reabsorbing HCO₃⁻, kidneys help regulate blood pH.
    • Water balance & ADH: Antidiuretic hormone (ADH) adjusts water reabsorption in collecting ducts to concentrate or dilute urine based on hydration status.
    • Blood pressure regulation: Kidneys influence blood volume (hence pressure) via renin-angiotensin mechanism (basic mention sufficient for Class 10).
    • Exam tip: Link urine concentration and ADH to hydration states for applied questions.
20. Question 20: Explain the role of stomata and guard cells in plants and how they respond to environmental conditions.

    Answer:

    • Stomata function: Pores on leaf surfaces for gas exchange (CO₂ uptake for photosynthesis, O₂ release) and transpiration control.
    • Guard cells: Specialized epidermal cells flanking stomatal pore; change shape by turgor pressure to open or close the pore.
    • Response to environment:
      • In light, guard cells accumulate K⁺ and water by osmosis → become turgid and open stomata (allow photosynthesis).
      • In darkness or water stress, guard cells lose turgor → stomata close to conserve water.
    • Exam tip: Describe mechanism briefly and relate stomatal behaviour to transpiration and photosynthesis trade-off.
21. Question 21: Describe the structure and role of the respiratory surface in humans and explain the features that make it efficient.

    Answer:

    • Respiratory surface: Alveoli in lungs — microscopic sacs at the end of bronchioles.
    • Features for efficiency:
      • Large total surface area (many alveoli) for diffusion.
      • Thin alveolar and capillary walls (one cell thick) for short diffusion distance.
      • Moist lining to dissolve gases and aid diffusion.
      • Rich capillary network to maintain concentration gradients of O₂ and CO₂.
    • Exam tip: Mention diffusion principles and role of surfactant (reduces surface tension) if asked.
22. Question 22: Explain how digestive disorders like indigestion and constipation occur and basic preventive measures.

    Answer:

    • Indigestion (dyspepsia): Poor digestion causing discomfort due to overeating, irregular eating, excessive fatty/spicy food; may result from inadequate enzyme activity or acid imbalance.
    • Constipation: Infrequent or difficult bowel movements due to low fibre diet, dehydration, lack of exercise, slow intestinal motility.
    • Prevention & basic remedies:
      • Balanced diet with adequate fibre and fluids, regular meals, moderate fat intake.
      • Regular physical activity to stimulate gut motility.
      • Seek medical advice for persistent symptoms; avoid self-medication with strong laxatives.
    • Exam tip: Relate causes to lifestyle and suggest simple preventive measures.
23. Question 23: Describe the role of liver in metabolism and how it supports digestion and detoxification.

    Answer:

    • Metabolic roles: Glycogen storage and release (regulates blood glucose), synthesis of plasma proteins and cholesterol.
    • Role in digestion: Produces bile which emulsifies fats aiding lipase action; bile salts facilitate absorption of fat breakdown products.
    • Detoxification: Converts harmful substances (e.g., ethanol, drugs) into less harmful forms for excretion; ammonia converted to urea (excreted by kidney).
    • Exam tip: Mention glycogen storage, bile production and detoxification succinctly.
24. Question 24: Explain the control of breathing and how chemoreceptors regulate respiration in response to CO₂ levels.

    Answer:

    • Control centres: Medulla oblongata and pons in brainstem regulate basic rhythm of breathing via neural signals to diaphragm and intercostal muscles.
    • Chemoreceptors: Central chemoreceptors in medulla respond to pH changes (due to CO₂ in cerebrospinal fluid); peripheral chemoreceptors in carotid and aortic bodies detect blood O₂ and CO₂ levels.
    • Response to increased CO₂: Raised CO₂ → increased H⁺ (lower pH) → chemoreceptors stimulate respiratory centre → increase rate and depth of breathing → more CO₂ expelled.
    • Exam tip: Emphasise CO₂ (not O₂) as primary driver of minute‑to‑minute respiratory control under normal conditions.
25. Question 25: Discuss the adaptive features of xerophytic plants that reduce water loss.

    Answer:

    • Xerophytic adaptations:
      • Thick cuticle on leaves to reduce evaporation.
      • Sunken stomata and reduced stomatal number to minimize water loss.
      • Leaves reduced to spines (as in cacti) or rolled leaves to reduce surface area.
      • Hairy leaf surfaces to trap moist air and reduce transpiration.
    • Function: These features decrease transpiration and help plants survive in arid conditions.
    • Exam tip: Give specific examples (cactus, xerophytes) and link each structural feature to its function.
26. Question 26: Explain how hormones regulate digestion and metabolism with two examples.

    Answer:

    • Gastrin: Secreted by stomach lining in response to food; stimulates secretion of gastric juice (HCl) and pepsinogen aiding protein digestion.
    • Insulin: Secreted by pancreatic β-cells when blood glucose is high; promotes glucose uptake by cells and storage as glycogen in liver and muscle, lowering blood glucose.
    • Glucagon: Secreted by α-cells of pancreas when blood glucose is low; stimulates glycogen breakdown and gluconeogenesis raising blood glucose.
    • Exam tip: Mention source, stimulus for release and principal action for each hormone.
27. Question 27: Describe the causes, symptoms and basic management of kidney stone (renal calculi).

    Answer:

    • Causes: Supersaturation of urine with minerals (calcium oxalate, uric acid), dehydration, dietary factors, metabolic disorders.
    • Symptoms: Severe flank pain radiating to groin, blood in urine (haematuria), nausea, urinary urgency or infection.
    • Basic management: Increased fluid intake, pain management, medical procedures (lithotripsy to break stones), surgical removal in severe cases; dietary advice to reduce stone-forming substances.
    • Exam tip: Briefly mention prevention: hydration and dietary modification (reduce excessive salt, oxalate-rich foods) as answer extension.
28. Question 28: Explain how plant roots are adapted for absorption of water and minerals.

    Answer:

    • Root hairs: Tiny extensions of epidermal cells increasing absorptive surface area significantly.
    • Thin cell walls and large vacuoles: Facilitate water uptake by osmosis into root cells.
    • Extensive branching: Greater soil contact allowing more efficient uptake of water and minerals.
    • Cortex and endodermis: Cortical cells store and transport water inward; Casparian strip in endodermis forces selective uptake through symplast pathway into xylem (regulation of minerals).
    • Exam tip: Mention osmotic gradient and role of root pressure as secondary mechanism for upward movement.
29. Question 29: Discuss the ecological and physiological importance of transpiration in plants.

    Answer:

    • Physiological roles:
      • Transpiration pull aids ascent of xylem sap (water and dissolved minerals) from roots to leaves.
      • Cooling effect: evaporation from leaf surfaces lowers leaf temperature.
      • Maintains turgor pressure and assists in mineral transport and nutrient distribution.
    • Ecological roles:
      • Influences local humidity and microclimate; links water cycle between soil, plants and atmosphere.
      • High transpiration rates in forests contribute to atmospheric moisture and regional rainfall patterns.
    • Exam tip: Give both plant-level and ecosystem-level effects to show depth of understanding.
30. Question 30: Prepare a concise answer summarising the key points of Chapter 5: Life Processes that a student must remember for the CBSE board exam.

    Answer — Key Points Summary:

    • Photosynthesis: Equation, sites (chloroplast), light vs dark reactions, factors affecting it.
    • Nutrition: Autotrophic vs heterotrophic; human digestion — organs and major enzymes, absorption in small intestine.
    • Respiration: Aerobic (glycolysis, Krebs, ETC) vs anaerobic (fermentation); ATP as energy currency.
    • Transport: Xylem & phloem functions, mass flow hypothesis, blood components and double circulation in humans.
    • Excretion & kidney: Nephron processes (filtration, reabsorption, secretion), ADH role, urine concentration.
    • Breathing & gas exchange: Mechanism of inhalation/exhalation, alveolar adaptations, transport of O₂/CO₂.
    • Practical tips: Practice labelled diagrams (leaf, chloroplast, nephron, heart), memorise equations and make short bullet-point answers for revision.

    Use this summary as your last-minute revision sheet — include diagrams and a couple of practice questions for a strong board performance.