ICSE – Grade 10 – Biology – Ch 06 – QA

Questions & Answers

ICSE - Grade - 10

Subject: Biology

Chapter - 06 - Photosynthesis - Provider for Food for All

Types of Questions

MCQ

  1. Which pigment is responsible for photosynthesis in plants?
     A. Carotene
     B. Xanthophyll
     C. Chlorophyll
     D. Anthocyanin
     Answer: C. Chlorophyll


  2. The organelle in which photosynthesis occurs is:
     A. Mitochondria
     B. Nucleus
     C. Chloroplast
     D. Ribosome
     Answer: C. Chloroplast


  3. Which gas is essential for photosynthesis?
     A. Oxygen
     B. Nitrogen
     C. Carbon dioxide
     D. Hydrogen
     Answer: C. Carbon dioxide


  4. Which of the following is NOT a product of photosynthesis?
     A. Glucose
     B. Oxygen
     C. Carbon dioxide
     D. Water
     Answer: C. Carbon dioxide


  5. Photosynthesis primarily occurs in which part of the leaf?
     A. Spongy mesophyll
     B. Palisade mesophyll
     C. Epidermis
     D. Veins
     Answer: B. Palisade mesophyll


  6. What is the source of oxygen released during photosynthesis?
     A. Carbon dioxide
     B. Glucose
     C. Water
     D. Chlorophyll
     Answer: C. Water


  7. The process of splitting water molecules using light energy is called:
     A. Hydrolysis
     B. Photolysis
     C. Glycolysis
     D. Plasmolysis
     Answer: B. Photolysis


  8. The light-dependent phase of photosynthesis takes place in the:
     A. Nucleus
     B. Stroma
     C. Grana
     D. Cytoplasm
     Answer: C. Grana


  9. The dark phase of photosynthesis occurs in the:
     A. Thylakoid
     B. Cytoplasm
     C. Grana
     D. Stroma
     Answer: D. Stroma


  10. Which element is actively involved in the opening of stomata?
     A. Calcium
     B. Sodium
     C. Potassium
     D. Magnesium
     Answer: C. Potassium


  11. Which of these is an internal factor affecting photosynthesis?
     A. Light intensity
     B. CO₂ concentration
     C. Chlorophyll content
     D. Temperature
     Answer: C. Chlorophyll content


  12. Which structure controls the opening and closing of stomata?
     A. Xylem
     B. Phloem
     C. Guard cells
     D. Mesophyll cells
     Answer: C. Guard cells


  13. Which of the following is used to test for the presence of starch in a leaf?
     A. Copper sulfate
     B. Iodine solution
     C. Lime water
     D. Alcohol
     Answer: B. Iodine solution


  14. What is the function of the extensive vein network in leaves?
     A. Photosynthesis
     B. Water and mineral transport
     C. Transpiration
     D. Gaseous exchange
     Answer: B. Water and mineral transport


  15. Which of the following processes is directly powered by sunlight?
     A. Formation of glucose
     B. Conversion of ATP to ADP
     C. Splitting of water
     D. Diffusion of gases
     Answer: C. Splitting of water


  16. Which theory explains stomatal opening based on sugar production?
     A. Pressure-flow theory
     B. Sugar concentration theory
     C. K⁺ ion exchange theory
     D. Mass flow hypothesis
     Answer: B. Sugar concentration theory


  17. What is the first stable product of the dark phase?
     A. Glucose
     B. Fructose
     C. 3-carbon compound
     D. Oxygen
     Answer: C. 3-carbon compound


  18. What happens to excess glucose in plants?
     A. Excreted
     B. Stored as starch
     C. Converted to proteins
     D. Lost as water
     Answer: B. Stored as starch


  19. Which of these is a waste product of photosynthesis?
     A. Glucose
     B. Carbon dioxide
     C. Oxygen
     D. Water
     Answer: C. Oxygen


  20. Which factor is NOT required in the dark phase?
     A. ATP
     B. NADPH
     C. Sunlight
     D. CO₂
     Answer: C. Sunlight


  21. What is the primary purpose of photosynthesis?
     A. To release oxygen
     B. To produce glucose
     C. To absorb CO₂
     D. To close stomata
     Answer: B. To produce glucose


  22. What is the role of sunlight in photosynthesis?
     A. Provides heat
     B. Splits glucose
     C. Powers photolysis of water
     D. Opens stomata
     Answer: C. Powers photolysis of water


  23. Which is not an adaptation of leaves for photosynthesis?
     A. Thick cuticle
     B. Large surface area
     C. Numerous stomata
     D. Thin leaves
     Answer: A. Thick cuticle


  24. Which is used to destarch a plant before experiment?
     A. Sunlight
     B. Boiling
     C. Darkness
     D. Iodine
     Answer: C. Darkness


  25. Presence of starch in a leaf indicates:
     A. High transpiration
     B. High CO₂
     C. Photosynthesis occurred
     D. Respiration occurred
     Answer: C. Photosynthesis occurred


  26. The raw materials for photosynthesis are:
     A. Oxygen and glucose
     B. Water and oxygen
     C. Carbon dioxide and water
     D. Glucose and carbon dioxide
     Answer: C. Carbon dioxide and water


  27. In which cells is the maximum number of chloroplasts found?
     A. Spongy mesophyll
     B. Guard cells
     C. Palisade mesophyll
     D. Lower epidermis
     Answer: C. Palisade mesophyll


  28. Carbon dioxide enters the plant mainly through:
     A. Root hairs
     B. Cuticle
     C. Stomata
     D. Veins
     Answer: C. Stomata


  29. The final stable sugar formed in photosynthesis is:
     A. Ribose
     B. Sucrose
     C. Glucose
     D. Fructose
     Answer: C. Glucose


  30. Starch is detected by the presence of what colour with iodine?
     A. Blue
     B. Blue-black
     C. Red
     D. Green
     Answer: B. Blue-black


  31. Which of the following is NOT a product of light-dependent reactions?
     A. Oxygen
     B. ATP
     C. NADPH
     D. Glucose
     Answer: D. Glucose


  32. What is removed from the leaf before the starch test?
     A. Glucose
     B. Iodine
     C. Chlorophyll
     D. Oxygen
     Answer: C. Chlorophyll


  33. The carbon in glucose comes from:
     A. Water
     B. Sunlight
     C. Chlorophyll
     D. Carbon dioxide
     Answer: D. Carbon dioxide


  34. Which theory involves ion movement during stomatal opening?
     A. Sugar concentration
     B. Osmotic pressure
     C. K⁺ ion theory
     D. Root pressure theory
     Answer: C. K⁺ ion theory


  35. What causes guard cells to become turgid?
     A. Loss of water
     B. Gain of sugar
     C. Water entering due to osmosis
     D. Absence of light
     Answer: C. Water entering due to osmosis


  36. Which is NOT a function of stomata?
     A. Photosynthesis
     B. Transpiration
     C. Gaseous exchange
     D. Absorption of nutrients
     Answer: D. Absorption of nutrients


  37. Why is the leaf boiled in alcohol during the starch test?
     A. To soften it
     B. To remove starch
     C. To remove chlorophyll
     D. To test for protein
     Answer: C. To remove chlorophyll


  38. Which of the following slows down photosynthesis?
     A. High CO₂
     B. Optimum temperature
     C. Low light intensity
     D. Presence of chlorophyll
     Answer: C. Low light intensity


  39. Where does photolysis occur?
     A. Cytoplasm
     B. Stroma
     C. Grana
     D. Ribosome
     Answer: C. Grana


  40. What is the effect of high temperature on photosynthesis?
     A. Increases indefinitely
     B. No effect
     C. Increases to a limit then drops
     D. Stops completely
     Answer: C. Increases to a limit then drops


  41. Which component is NOT directly used in photosynthesis?
     A. Sunlight
     B. Nitrogen
     C. Water
     D. CO₂
     Answer: B. Nitrogen


  42. Photosynthesis is an example of:
     A. Catabolic reaction
     B. Anabolic reaction
     C. Respiratory process
     D. None of the above
     Answer: B. Anabolic reaction


  43. The best light for photosynthesis is:
     A. Green
     B. Yellow
     C. Blue and red
     D. Violet
     Answer: C. Blue and red


  44. During photosynthesis, water is mainly absorbed through:
     A. Stomata
     B. Cuticle
     C. Veins
     D. Roots
     Answer: D. Roots


  45. Which experiment shows that CO₂ is necessary for photosynthesis?
     A. Bell jar experiment
     B. Alcohol boiling
     C. Black paper experiment
     D. KOH in flask with leaf
     Answer: D. KOH in flask with leaf


  46. Which is the immediate product of light reaction?
     A. Oxygen
     B. ATP and NADPH
     C. Glucose
     D. CO₂
     Answer: B. ATP and NADPH


  47. Which is NOT an end product of the light-independent phase?
     A. Glucose
     B. Oxygen
     C. Water
     D. ADP
     Answer: B. Oxygen


  48. Which gas is absorbed during photosynthesis?
     A. CO₂
     B. O₂
     C. N₂
     D. H₂
     Answer: A. CO₂


  49. In destarching, plants are kept in dark for:
     A. 6 hours
     B. 12 hours
     C. 24 hours
     D. 48-72 hours
     Answer: D. 48–72 hours


  50. What is the ultimate source of energy for photosynthesis?
     A. CO₂
     B. Water
     C. Sunlight
     D. Chlorophyll
     Answer: C. Sunlight

Fill in the Blanks

  1. Photosynthesis occurs in the ______ of plant cells.
     Answer: chloroplasts


  2. The green pigment essential for photosynthesis is ______.
     Answer: chlorophyll


  3. The gas absorbed during photosynthesis is ______.
     Answer: carbon dioxide


  4. The gas released during photosynthesis is ______.
     Answer: oxygen


  5. The main product of photosynthesis is ______.
     Answer: glucose


  6. The splitting of water molecules during photosynthesis is called ______.
     Answer: photolysis


  7. The organelle responsible for photosynthesis is ______.
     Answer: chloroplast


  8. The light-dependent phase occurs in the ______ of the chloroplast.
     Answer: grana


  9. The light-independent phase occurs in the ______ of the chloroplast.
     Answer: stroma


  10. The structure that controls the opening and closing of stomata is the ______.
     Answer: guard cells


  11. In the iodine test, starch gives a ______ colour.
     Answer: blue-black


  12. The process of making a plant starch-free before an experiment is called ______.
     Answer: destarching


  13. During photosynthesis, ______ energy is converted into chemical energy.
     Answer: light


  14. The immediate products of the light reaction are ______ and NADPH.
     Answer: ATP


  15. ______ is the process by which plants prepare their own food.
     Answer: Photosynthesis


  16. The gas released during photolysis is ______.
     Answer: oxygen


  17. In photosynthesis, CO₂ is reduced to form ______.
     Answer: glucose


  18. The ______ theory explains stomatal opening due to sugar formation.
     Answer: sugar concentration


  19. The ______ ion theory explains stomatal opening based on ion movement.
     Answer: potassium


  20. Leaves are adapted for photosynthesis by having a large ______.
     Answer: surface area


  21. ______ is the stable form in which glucose is stored in plants.
     Answer: starch


  22. Stomata are mostly found on the ______ surface of leaves.
     Answer: lower


  23. ______ helps in the transport of water to leaf cells.
     Answer: xylem


  24. The energy currency formed during the light reaction is ______.
     Answer: ATP


  25. The cells rich in chloroplasts and responsible for photosynthesis are the ______ mesophyll cells.
     Answer: palisade


  26. The part of the leaf that is transparent to allow light penetration is the ______.
     Answer: epidermis


  27. Water is absorbed by the ______ of plants.
     Answer: roots


  28. The chemical used to test the presence of starch is ______.
     Answer: iodine


  29. Photosynthesis is an ______ type of reaction.
     Answer: anabolic


  30. A destarched plant is kept in ______ for 48-72 hours.
     Answer: darkness


  31. In the carbon cycle, plants remove ______ from the atmosphere.
     Answer: carbon dioxide


  32. In the dark phase, glucose is formed using CO₂ and ______.
     Answer: ATP


  33. Excessive sunlight can destroy chlorophyll by a process called ______.
     Answer: photobleaching


  34. The most effective light for photosynthesis is ______ and red.
     Answer: blue


  35. The leaf veins contain xylem and ______.
     Answer: phloem


  36. Water is one of the raw materials and also a ______ of photosynthesis.
     Answer: by-product


  37. The first stable compound formed in the dark phase is a ______ compound.
     Answer: 3-carbon


  38. The epidermis of a leaf is covered with a ______ to reduce water loss.
     Answer: cuticle


  39. ______ is the process that returns CO₂ to the atmosphere in the carbon cycle.
     Answer: respiration


  40. CO₂ enters the leaf through small pores called ______.
     Answer: stomata


  41. A chloroplast contains grana and ______.
     Answer: stroma


  42. The process opposite to photosynthesis is ______.
     Answer: respiration


  43. Glucose produced during photosynthesis is used for energy or stored as ______.
     Answer: starch


  44. The ______ of leaf cells contain chlorophyll for trapping sunlight.
     Answer: chloroplasts


  45. Leaf arrangement avoids ______ to ensure maximum light absorption.
     Answer: overlapping


  46. Water moves into guard cells due to ______.
     Answer: osmosis


  47. The ______ phase of photosynthesis does not require direct light.
     Answer: light-independent


  48. In the dark phase, ______ is fixed into glucose.
     Answer: carbon dioxide


  49. The extensive ______ system in a leaf helps in quick transport of materials.
     Answer: vein


  50. Photosynthesis helps maintain a balance of oxygen and ______ in the atmosphere.
     Answer: carbon dioxide

Name the Following

  1. Name the green pigment essential for photosynthesis.
     Answer: Chlorophyll


  2. Name the organelle where photosynthesis takes place.
     Answer: Chloroplast


  3. Name the gas required for photosynthesis.
     Answer: Carbon dioxide


  4. Name the gas released during photosynthesis.
     Answer: Oxygen


  5. Name the main product of photosynthesis.
     Answer: Glucose


  6. Name the process by which plants make their food.
     Answer: Photosynthesis


  7. Name the part of chloroplast where light-dependent reactions occur.
     Answer: Grana


  8. Name the part of chloroplast where dark reactions occur.
     Answer: Stroma


  9. Name the cells that control the opening and closing of stomata.
     Answer: Guard cells


  10. Name the theory explaining stomatal movement due to sugar formation.
     Answer: Sugar concentration theory


  11. Name the theory explaining stomatal movement due to ion accumulation.
     Answer: Potassium ion concentration theory


  12. Name the experiment used to remove starch from a leaf.
     Answer: Destarching


  13. Name the test used to detect starch in leaves.
     Answer: Iodine test


  14. Name the type of plant nutrition shown by green plants.
     Answer: Autotrophic nutrition


  15. Name the coloured chemical used in the starch test.
     Answer: Iodine solution


  16. Name the process that splits water molecules using light.
     Answer: Photolysis


  17. Name the compound that stores energy during the light reaction.
     Answer: ATP (Adenosine Triphosphate)


  18. Name the ion responsible for osmotic movement in guard cells.
     Answer: Potassium ion (K⁺)


  19. Name the waste product of photosynthesis.
     Answer: Oxygen


  20. Name the sugar that is immediately formed in the photosynthesis process.
     Answer: Glucose


  21. Name the polysaccharide in which excess glucose is stored.
     Answer: Starch


  22. Name the part of the leaf that allows gaseous exchange.
     Answer: Stomata


  23. Name the atmospheric gas that is reduced in photosynthesis.
     Answer: Carbon dioxide


  24. Name the molecule that provides hydrogen during photosynthesis.
     Answer: Water


  25. Name the two phases of photosynthesis.
     Answer: Light-dependent phase and Light-independent phase


  26. Name the part of the leaf rich in chloroplasts.
     Answer: Palisade mesophyll


  27. Name the transparent protective layer on the leaf surface.
     Answer: Cuticle


  28. Name the fluid-filled part of chloroplast where CO₂ is fixed.
     Answer: Stroma


  29. Name the pigment that traps sunlight.
     Answer: Chlorophyll


  30. Name the energy-rich molecules produced in the light reaction.
     Answer: ATP and NADPH


  31. Name one external factor affecting photosynthesis.
     Answer: Light intensity


  32. Name one internal factor affecting photosynthesis.
     Answer: Chlorophyll content


  33. Name the cycle that involves photosynthesis and respiration.
     Answer: Carbon cycle


  34. Name the tissues that transport water to leaves.
     Answer: Xylem


  35. Name the tissues that carry glucose away from the leaf.
     Answer: Phloem


  36. Name one adaptation of leaves for maximum photosynthesis.
     Answer: Large surface area


  37. Name the experiment that shows CO₂ is essential for photosynthesis.
     Answer: Bell jar experiment with KOH


  38. Name the coloured layer that may cause photobleaching when exposed to excess light.
     Answer: Chlorophyll


  39. Name the compound used to remove chlorophyll from leaves during the starch test.
     Answer: Alcohol


  40. Name the phase where CO₂ is fixed into glucose.
     Answer: Light-independent phase


  41. Name one by-product of photolysis.
     Answer: Oxygen


  42. Name the test in which the leaf turns blue-black if starch is present.
     Answer: Iodine test


  43. Name the process opposite to photosynthesis.
     Answer: Respiration


  44. Name the type of reaction photosynthesis is categorized under.
     Answer: Anabolic reaction


  45. Name the sugar formed that is transported through phloem.
     Answer: Sucrose


  46. Name the structure that prevents overlapping of leaves.
     Answer: Leaf arrangement on stem


  47. Name the product that serves as a food reserve in plants.
     Answer: Starch


  48. Name the energy source for the light-dependent phase.
     Answer: Sunlight


  49. Name the process responsible for turgidity in guard cells.
     Answer: Osmosis


  50. Name the major elements required for photosynthesis.
     Answer: Carbon, Hydrogen, and Oxygen

Answer in One Word

  1. Which pigment absorbs light for photosynthesis?
     Answer: Chlorophyll


  2. Site of photosynthesis in a plant cell?
     Answer: Chloroplast


  3. Gas used during photosynthesis?
     Answer: Carbon dioxide


  4. Gas released during photosynthesis?
     Answer: Oxygen


  5. Simple sugar produced by photosynthesis?
     Answer: Glucose


  6. Type of nutrition in green plants?
     Answer: Autotrophic


  7. Organ that contains most chloroplasts in plants?
     Answer: Leaf


  8. Phase of photosynthesis that requires light?
     Answer: Photochemical


  9. Phase of photosynthesis that does not need light?
     Answer: Biosynthetic


  10. Tissue transporting water to leaves?
     Answer: Xylem


  11. Tissue transporting food from leaves?
     Answer: Phloem


  12. Opening on leaves for gas exchange?
     Answer: Stomata


  13. Cells controlling stomatal opening?
     Answer: Guard cells


  14. Product stored from excess glucose?
     Answer: Starch


  15. Energy molecule formed during light reaction?
     Answer: ATP


  16. Process of breaking water using light?
     Answer: Photolysis


  17. Colour of iodine-starch complex?
     Answer: Blue-black


  18. Type of reaction – photosynthesis?
     Answer: Anabolic


  19. Type of compound first formed in dark phase?
     Answer: Carbohydrate


  20. One internal factor affecting photosynthesis?
     Answer: Chlorophyll


  21. Process reverse of photosynthesis?
     Answer: Respiration


  22. Energy source for photosynthesis?
     Answer: Sunlight


  23. Solution used to remove chlorophyll?
     Answer: Alcohol


  24. Theory based on ion movement in guard cells?
     Answer: Potassium


  25. Liquid part of chloroplast?
     Answer: Stroma


  26. Structure in chloroplast where photolysis occurs?
     Answer: Grana


  27. Protective transparent layer of the leaf?
     Answer: Cuticle


  28. One external factor affecting photosynthesis?
     Answer: Light


  29. Initial product of light reaction besides ATP?
     Answer: NADPH


  30. Scientific name of photosynthesis end product?
     Answer: C₆H₁₂O₆


  31. Process by which water enters guard cells?
     Answer: Osmosis


  32. Shape of guard cells in dicots?
     Answer: Kidney


  33. Colour of chlorophyll?
     Answer: Green


  34. Process that balances atmospheric CO₂ and O₂?
     Answer: Photosynthesis


  35. Movement of water in plants?
     Answer: Ascent


  36. Region in the leaf with maximum chloroplasts?
     Answer: Palisade


  37. Reaction occurring in grana?
     Answer: Light-dependent


  38. Common test for presence of starch?
     Answer: Iodine


  39. Component removed before starch test?
     Answer: Chlorophyll


  40. Gas released in photolysis?
     Answer: Oxygen


  41. Food-conducting tissue?
     Answer: Phloem


  42. Water-conducting tissue?
     Answer: Xylem


  43. Product formed from CO₂ in dark phase?
     Answer: Glucose


  44. Theory involving sugar build-up in guard cells?
     Answer: Sugar


  45. Part of leaf allowing light penetration?
     Answer: Epidermis


  46. Main function of chloroplast?
     Answer: Photosynthesis


  47. Veins of leaf contain ______ and phloem.
     Answer: Xylem


  48. Ion involved in stomatal opening?
     Answer: Potassium


  49. Product transported to storage organs?
     Answer: Sucrose


  50. Leaf surface where most stomata are found?
     Answer: Lower

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Find the Odd Man Out

  1. ATP, NADPH, Glucose, Oxygen
     Answer: Glucose
     Explanation: Glucose is formed in the dark phase; others are products of the light phase.


  2. Xylem, Phloem, Stomata, Cambium
     Answer: Stomata
     Explanation: Stomata is not a vascular tissue; others are parts of vascular bundles.


  3. Grana, Stroma, Mitochondria, Chloroplast
     Answer: Mitochondria
     Explanation: Mitochondria is not part of the chloroplast.


  4. Photolysis, Osmosis, Diffusion, Transpiration
     Answer: Photolysis
     Explanation: Photolysis is a light-dependent chemical reaction; others are physical processes.


  5. Chlorophyll, Carotene, Xanthophyll, Insulin
     Answer: Insulin
     Explanation: Insulin is a hormone, not a pigment.


  6. Guard cells, Palisade cells, Spongy mesophyll, Root hair cells
     Answer: Root hair cells
     Explanation: Root hair cells are not part of the leaf structure.


  7. Sunlight, Water, CO₂, Protein
     Answer: Protein
     Explanation: Protein is not a raw material for photosynthesis.


  8. Light, CO₂, O₂, Water
     Answer: O₂
     Explanation: Oxygen is a product, not a raw material.


  9. Alcohol, Iodine, Water, Glucose
     Answer: Glucose
     Explanation: Glucose is not used in the starch test; others are.


  10. ATP, NADPH, Oxygen, Starch
     Answer: Starch
     Explanation: Starch is a storage product, not a direct product of light phase.


  11. Cuticle, Stomata, Vein, Chloroplast
     Answer: Chloroplast
     Explanation: Chloroplast is a cell organelle; others are leaf structures.


  12. K⁺ ions, Sugar, ATP, Guard cells
     Answer: ATP
     Explanation: ATP does not directly regulate stomatal opening.


  13. Darkness, CO₂, Sunlight, Water
     Answer: Darkness
     Explanation: Darkness cannot drive photosynthesis; others are required.


  14. Respiration, Photosynthesis, Glycolysis, Fermentation
     Answer: Photosynthesis
     Explanation: Photosynthesis is an anabolic process; others are catabolic.


  15. CO₂, Oxygen, ATP, Glucose
     Answer: CO₂
     Explanation: CO₂ is a raw material; others are products.


  16. Iodine, Starch, Chlorophyll, Alcohol
     Answer: Starch
     Explanation: Starch is the substance tested, not used in the test.


  17. Grana, Stroma, Thylakoid, Cytoplasm
     Answer: Cytoplasm
     Explanation: Cytoplasm is not part of the chloroplast.


  18. Light-dependent phase, Light-independent phase, Respiration, Carbon fixation
     Answer: Respiration
     Explanation: Respiration is not a part of photosynthesis.


  19. NADP, CO₂, ATP, KOH
     Answer: KOH
     Explanation: KOH is used in experiments, not a participant in photosynthesis.


  20. Chlorophyll, Chloroplast, Oxygen, Glucose
     Answer: Chloroplast
     Explanation: Chloroplast is the site; others are involved substances.


  21. Leaf blade, Petiole, Guard cells, Midrib
     Answer: Guard cells
     Explanation: Guard cells are cellular; others are leaf parts.


  22. Water, CO₂, Oxygen, Chlorophyll
     Answer: Oxygen
     Explanation: Oxygen is an output, others are inputs.


  23. Carbon dioxide, Sunlight, Protein, Water
     Answer: Protein
     Explanation: Protein is not involved in photosynthesis directly.


  24. Alcohol, Boiling water, KOH, Iodine
     Answer: KOH
     Explanation: KOH is not used in starch test, but in CO₂ requirement experiment.


  25. Mesophyll, Grana, Stroma, Mitochondria
     Answer: Mitochondria
     Explanation: Mitochondria is not involved in photosynthesis.


  26. Sugar, Starch, Sucrose, Amino acid
     Answer: Amino acid
     Explanation: Amino acid is not a carbohydrate.


  27. Root, Leaf, Guard cells, Chloroplast
     Answer: Root
     Explanation: Roots do not perform photosynthesis.


  28. Vein, Xylem, Phloem, Ribosome
     Answer: Ribosome
     Explanation: Ribosome is not a vascular component.


  29. Bell jar, Alcohol, KOH, Thermometer
     Answer: Thermometer
     Explanation: Thermometer is not used in photosynthesis experiments.


  30. CO₂, Sunlight, Water, Oxygen
     Answer: Oxygen
     Explanation: Oxygen is an output, others are inputs.


  31. Xylem, Phloem, Guard cells, Pith
     Answer: Guard cells
     Explanation: Guard cells regulate stomata, not transport.


  32. Glucose, Oxygen, ATP, NADPH
     Answer: Glucose
     Explanation: Glucose is made in dark phase; others in light phase.


  33. Blue-black, Yellow, Green, Red
     Answer: Blue-black
     Explanation: Only blue-black is a starch test result.


  34. Photosynthesis, Combustion, Respiration, Fermentation
     Answer: Photosynthesis
     Explanation: Only photosynthesis consumes CO₂.


  35. Light, Temperature, Enzyme, Sugar
     Answer: Sugar
     Explanation: Sugar is a product, not a factor.


  36. Root hairs, Stomata, Cuticle, Leaf blade
     Answer: Root hairs
     Explanation: Root hairs are underground, others are in leaves.


  37. Chlorophyll, CO₂, NADPH, Iron
     Answer: Iron
     Explanation: Iron is not directly required in photosynthesis.


  38. Sucrose, Glucose, Cellulose, Oxygen
     Answer: Oxygen
     Explanation: Oxygen is not a carbohydrate.


  39. Photosynthesis, Carbon cycle, Combustion, Reproduction
     Answer: Reproduction
     Explanation: Reproduction is unrelated to the carbon cycle.


  40. CO₂, H₂O, O₂, Ethanol
     Answer: Ethanol
     Explanation: Ethanol is not a raw material or product of photosynthesis.


  41. Palisade, Stroma, Guard cells, Phloem
     Answer: Phloem
     Explanation: Phloem does not contain chloroplasts.


  42. Bell jar, KOH, Alcohol, Thermometer
     Answer: Thermometer
     Explanation: Thermometer is not needed in photosynthesis experiments.


  43. Cuticle, Chloroplast, Epidermis, Petiole
     Answer: Chloroplast
     Explanation: Chloroplast is a cell organelle; others are leaf parts.


  44. Carbon dioxide, Oxygen, Glucose, Sodium
     Answer: Sodium
     Explanation: Sodium is not involved in photosynthesis.


  45. Root, Stem, Leaf, Flower
     Answer: Leaf
     Explanation: Only leaf performs photosynthesis.


  46. Light, Dark, Photolysis, Chloroplast
     Answer: Dark
     Explanation: Dark phase does not need light.


  47. Sunlight, KOH, CO₂, Water
     Answer: KOH
     Explanation: KOH is not a natural component of photosynthesis.


  48. Carbon dioxide, Water, Glucose, Starch
     Answer: Carbon dioxide
     Explanation: Only CO₂ is a gas; others are solids/liquids.


  49. ATP, Protein, NADPH, Light
     Answer: Protein
     Explanation: Protein is not produced in photosynthesis.


  50. Autotroph, Chloroplast, Chlorophyll, Mitochondria
     Answer: Mitochondria
     Explanation: Mitochondria is not involved in photosynthesis.

Match the Pair

Set 1 – Match the Pairs

Column A

  1. Chlorophyll
  2. Guard cells
  3. ATP
  4. Stomata
  5. Grana

Column B
 a. Site of light reaction
 b. Absorbs sunlight
 c. Controls stomatal movement
 d. Energy currency
 e. Opening in the leaf surface

Correct Answers – Set 1
 1 – b
 2 – c
 3 – d
 4 – e
 5 – a

Set 2 – Match the Pairs

Column A

  1. Carbon dioxide
  2. Photolysis
  3. Palisade layer
  4. Oxygen
  5. Stroma

Column B
 a. Site of dark phase
 b. Gas released during photosynthesis
 c. Gas used in photosynthesis
 d. Found below upper epidermis
 e. Splitting of water

Correct Answers – Set 2
 1 – c
 2 – e
 3 – d
 4 – b
 5 – a

Set 3 – Match the Pairs

Column A

  1. Photosynthesis
  2. NADPH
  3. Xylem
  4. Iodine solution
  5. Alcohol

Column B
 a. Removes chlorophyll
 b. Detects starch
 c. Carries water
 d. Process that forms glucose
 e. Hydrogen carrier

Correct Answers – Set 3
 1 – d
 2 – e
 3 – c
 4 – b
 5 – a

Set 4 – Match the Pairs

Column A

  1. Leaf adaptations
  2. Cuticle
  3. Dark phase
  4. Sunlight
  5. Chloroplast

Column B
 a. Double membrane organelle
 b. Site of glucose formation
 c. Large surface area
 d. Transparent to light
 e. Energy source for photosynthesis

Correct Answers – Set 4
 1 – c
 2 – d
 3 – b
 4 – e
 5 – a

Set 5 – Match the Pairs

Column A

  1. Bell jar experiment
  2. KOH
  3. Root hair
  4. Phloem
  5. Mesophyll

Column B
 a. Absorbs CO₂
 b. CO₂ essential for photosynthesis
 c. Transports food
 d. Absorbs water
 e. Contains chloroplasts

Correct Answers – Set 5
 1 – b
 2 – a
 3 – d
 4 – c
 5 – e

Set 6 – Match the Pairs

Column A

  1. Glucose
  2. Starch
  3. Respiration
  4. Fermentation
  5. Oxygen

Column B
 a. Stored form of carbohydrate
 b. Energy-releasing process
 c. Anaerobic breakdown
 d. Photosynthesis by-product
 e. Simple sugar

Correct Answers – Set 6
 1 – e
 2 – a
 3 – b
 4 – c
 5 – d

Set 7 – Match the Pairs

Column A

  1. Potassium ion theory
  2. Sugar concentration theory
  3. Epidermis
  4. Vein
  5. Midrib

Column B
 a. Transport of water and food
 b. Main leaf vein
 c. Involved in stomatal opening
 d. Outer transparent layer
 e. Explains turgidity of guard cells

Correct Answers – Set 7
 1 – c
 2 – e
 3 – d
 4 – a
 5 – b

Set 8 – Match the Pairs

Column A

  1. Destarching
  2. Iodine test
  3. CO₂ fixation
  4. Water
  5. Leaf blade

Column B
 a. Starch detection
 b. Dark phase activity
 c. Broad surface for light absorption
 d. Removed by keeping in dark
 e. Raw material for photolysis

Correct Answers – Set 8
 1 – d
 2 – a
 3 – b
 4 – e
 5 – c

Set 9 – Match the Pairs

Column A

  1. Autotroph
  2. Light reaction
  3. Osmosis
  4. Blue and red light
  5. Green light

Column B
 a. Least absorbed
 b. Absorbed by chlorophyll
 c. Movement of water into guard cells
 d. Energy trapping stage
 e. Self food-making organism

Correct Answers – Set 9
 1 – e
 2 – d
 3 – c
 4 – b
 5 – a

Set 10 – Match the Pairs

Column A

  1. Spongy mesophyll
  2. Chlorophyll
  3. Carbon cycle
  4. Enzyme
  5. Glucose transport

Column B
 a. Food-conducting tissue
 b. Balances CO₂ and O₂
 c. Absorbs light
 d. Facilitates reactions
 e. Gas exchange space

Correct Answers – Set 10
 1 – e
 2 – c
 3 – b
 4 – d
 5 – a

Short Answer Questions  

  1. What is photosynthesis?
     Answer: Photosynthesis is the process by which green plants use carbon dioxide, water, and sunlight to produce glucose and oxygen.


  2. Name the pigment responsible for photosynthesis.
     Answer: Chlorophyll


  3. What are the raw materials of photosynthesis?
     Answer: Carbon dioxide and water


  4. What are the end products of photosynthesis?
     Answer: Glucose and oxygen


  5. Where does the light-dependent phase of photosynthesis occur?
     Answer: Grana of chloroplasts


  6. Where does the dark phase of photosynthesis occur?
     Answer: Stroma of chloroplasts


  7. What is the function of stomata in photosynthesis?
     Answer: Stomata allow the entry of carbon dioxide and the exit of oxygen and water vapour.


  8. What is the role of sunlight in photosynthesis?
     Answer: Sunlight provides energy for the light-dependent reactions.


  9. What is the importance of chlorophyll in photosynthesis?
     Answer: Chlorophyll absorbs light energy required for photosynthesis.


  10. What is photolysis?
     Answer: Photolysis is the splitting of water molecules using light energy to release hydrogen and oxygen.


  11. What is the function of ATP in photosynthesis?
     Answer: ATP provides energy for the synthesis of glucose in the dark phase.


  12. What is meant by the dark phase of photosynthesis?
     Answer: The dark phase is the light-independent phase where CO₂ is fixed into glucose using ATP and NADPH.


  13. Why are leaves called the food factories of plants?
     Answer: Because they synthesize food through photosynthesis.


  14. What is the function of guard cells?
     Answer: Guard cells regulate the opening and closing of stomata.


  15. What is destarching?
     Answer: Destarching is the process of removing starch from a plant by keeping it in darkness.


  16. Name the test used to detect the presence of starch in a leaf.
     Answer: Iodine test


  17. What colour indicates the presence of starch in a leaf?
     Answer: Blue-black


  18. What is the role of KOH in the experiment to show the need of CO₂ in photosynthesis?
     Answer: KOH absorbs carbon dioxide from the air.


  19. Name the cell organelle where photosynthesis occurs.
     Answer: Chloroplast


  20. Why is the leaf boiled in alcohol during the starch test?
     Answer: To remove chlorophyll so that iodine can react with starch.


  21. Which part of the leaf contains maximum chloroplasts?
     Answer: Palisade mesophyll


  22. Define autotrophic nutrition.
     Answer: Nutrition in which organisms prepare their own food using inorganic substances.


  23. Name the phase of photosynthesis where ATP is produced.
     Answer: Light-dependent phase


  24. Name the two products formed in the light-dependent phase.
     Answer: ATP and NADPH


  25. Which gas is absorbed during photosynthesis?
     Answer: Carbon dioxide


  26. Which gas is released during photosynthesis?
     Answer: Oxygen


  27. What is the importance of photosynthesis for animals?
     Answer: It provides oxygen and forms the base of the food chain.


  28. What is the role of the cuticle in a leaf?
     Answer: It protects the leaf and allows light to pass through.


  29. Mention one adaptation of leaves for photosynthesis.
     Answer: Large surface area to absorb more sunlight.


  30. What is the function of xylem in leaves?
     Answer: To transport water and minerals to the leaf cells.


  31. What is the function of phloem in leaves?
     Answer: To transport food from the leaves to other parts of the plant.


  32. What is meant by carbon fixation?
     Answer: Conversion of CO₂ into glucose in the dark phase.


  33. What is meant by the term ‘photochemical phase’?
     Answer: Light-dependent phase of photosynthesis where light energy is absorbed and converted into chemical energy.


  34. Which compound acts as a hydrogen carrier in photosynthesis?
     Answer: NADPH


  35. Why is light essential for photosynthesis?
     Answer: It provides energy to drive the photolysis of water and formation of ATP and NADPH.


  36. What is the fate of glucose formed in photosynthesis?
     Answer: It is used for energy, stored as starch, or converted to other organic compounds.


  37. What are grana?
     Answer: Stacks of thylakoid membranes within chloroplasts where light reactions occur.


  38. What are the functions of stroma?
     Answer: It contains enzymes for the dark phase and is the site of CO₂ fixation.


  39. How does CO₂ enter a plant?
     Answer: Through the stomata present on the leaves.


  40. What is the role of osmosis in guard cells?
     Answer: Osmosis causes guard cells to swell and open the stomata.


  41. What is the sugar concentration theory?
     Answer: Theory that explains stomatal opening due to sugar accumulation increasing osmotic pressure.


  42. What is the potassium ion theory?
     Answer: Theory that explains stomatal movement by the movement of K⁺ ions into guard cells.


  43. Which colour of light is least effective in photosynthesis?
     Answer: Green light


  44. Why is starch not directly transported in plants?
     Answer: Because starch is insoluble and must be converted into soluble sugars like sucrose.


  45. What is the purpose of boiling the leaf in hot water before the alcohol step?
     Answer: To kill the cells and stop metabolic activities.


  46. What is meant by ‘autotroph’?
     Answer: An organism that makes its own food using inorganic substances.


  47. Which part of the chloroplast contains chlorophyll?
     Answer: Thylakoid membranes


  48. What is the role of mesophyll cells in photosynthesis?
     Answer: They contain chloroplasts and carry out photosynthesis.


  49. What is meant by the term ‘anabolic process’?
     Answer: A process that builds up complex molecules from simpler ones using energy.


  50. Why is the photosynthesis process important for the carbon cycle?
     Answer: It helps remove CO₂ from the atmosphere and convert it into organic matter.

Puzzles

  1. I am the pigment that traps sunlight, but I’m not found in roots. Who am I?
     Answer: Chlorophyll


  2. Rearrange the letters to name a process: “SYEISNPHOOTST”
     Answer: Photosynthesis


  3. I am released during photosynthesis but not used by the plant. Who am I?
     Answer: Oxygen


  4. Find the odd one out: ATP, NADPH, Oxygen, Starch
     Answer: Starch (Product of dark phase; others are from light phase)


  5. I have two guard cells but no brain. I decide when to open or close. What am I?
     Answer: Stoma


  6. Decode me: I occur in the grana, I need light, and I produce ATP. What phase am I?
     Answer: Light-dependent phase


  7. I start with “C” and get fixed in the dark. What am I?
     Answer: Carbon dioxide


  8. Unscramble to find the site of photosynthesis: “SLPHTORHAC”
     Answer: Chloroplast


  9. I’m made from glucose, stored in leaves, and tested with iodine. Who am I?
     Answer: Starch


  10. Riddle: I am green, I reflect what I absorb the least, I live in cells. Who am I?
     Answer: Chlorophyll


  11. I am a theory involving sugar in guard cells. What theory am I?
     Answer: Sugar concentration theory


  12. I’m a test that turns blue-black in presence of starch. What test am I?
     Answer: Iodine test


  13. I’m split using light. My parts are used to make sugar and oxygen. Who am I?
     Answer: Water (H₂O)


  14. Find the word: Begins with P, ends with S, creates glucose in green parts.
     Answer: Photosynthesis


  15. Unscramble this molecule: “LGOUSEC”
     Answer: Glucose


  16. Guess who: I’m thin, flat, and have veins. I make food.
     Answer: Leaf


  17. I am essential for the dark phase but made in the light. Who am I?
     Answer: ATP


  18. What comes next in the sequence? Light → Chlorophyll → ?
     Answer: Photolysis


  19. I carry water upward in plants. I start with X. Who am I?
     Answer: Xylem


  20. Identify me: I am clear, protect the leaf, and let sunlight in.
     Answer: Cuticle


  21. Decode this: “EEGRN HGLTI” – least effective in photosynthesis.
     Answer: Green light


  22. Riddle: I’m the gas plants take in to make sugar.
     Answer: Carbon dioxide


  23. Rearranged organelle: “RAMTOHCONIAD”
     Answer: Mitochondria


  24. I conduct food, begin with ‘P’, and found in veins.
     Answer: Phloem


  25. I am formed in dark phase and stored as starch. Who am I?
     Answer: Glucose


  26. I’m the phase where CO₂ becomes sugar.
     Answer: Dark phase


  27. My initials are KOH. What is my job in experiments?
     Answer: Absorb carbon dioxide


  28. I am needed for photosynthesis, but in excess, I cause stomata to close.
     Answer: Water


  29. I make the leaf green. My name ends in “-yll.”
     Answer: Chlorophyll


  30. Find me in the leaf: I have gaps for air, found in mesophyll.
     Answer: Spongy mesophyll


  31. Connect the logic: CO₂ + H₂O + Sunlight = ?
     Answer: Glucose + O₂ (Photosynthesis)


  32. Find the relation: Grana : Light phase :: Stroma : ?
     Answer: Dark phase


  33. I am a part of chloroplast, where enzymes live. What am I?
     Answer: Stroma


  34. Name me: I enter leaves, I help make sugar, I’m absorbed from soil.
     Answer: Water


  35. Think! If I remove green pigment, which chemical am I?
     Answer: Alcohol


  36. I’m the colour of light chlorophyll reflects.
     Answer: Green


  37. What is common among ATP, NADPH, and sunlight?
     Answer: All are involved in light-dependent reactions


  38. Guess the phase: Doesn’t need light, makes sugar.
     Answer: Light-independent phase


  39. Riddle: My job is to capture sunlight in chloroplasts.
     Answer: Chlorophyll


  40. Decode the organ: “LFESAV”
     Answer: Leaves


  41. I’m the most common sugar produced in photosynthesis.
     Answer: Glucose


  42. Which plant tissue helps in food transport?
     Answer: Phloem


  43. I’m a waxy, non-cellular layer on the leaf.
     Answer: Cuticle


  44. Riddle: I form stacks called grana inside chloroplasts.
     Answer: Thylakoids


  45. Complete me: Sunlight + ? + Water = Photosynthesis
     Answer: Carbon dioxide


  46. I start with “A” and store energy during photosynthesis.
     Answer: ATP


  47. Identify me: I fix carbon, I’m enzyme-driven, I need NADPH.
     Answer: Dark phase


  48. Which phase produces O₂, ATP, and NADPH?
     Answer: Light-dependent phase


  49. I am a leaf opening, I allow gases in and out.
     Answer: Stoma (Stomata)


  50. My presence proves photosynthesis. I turn iodine blue-black.
     Answer: Starch

Difference Between:

  1. Difference between Autotrophs and Heterotrophs
     Autotrophs are organisms that prepare their own food using inorganic substances like carbon dioxide and water through photosynthesis (e.g., green plants). Heterotrophs are organisms that depend on other organisms for their food (e.g., animals, fungi).


  2. Difference between Light-dependent and Light-independent phases
     The light-dependent phase requires sunlight and occurs in the grana of chloroplasts, producing ATP, NADPH, and oxygen. The light-independent phase does not require light, occurs in the stroma, and uses ATP and NADPH to fix CO₂ into glucose.


  3. Difference between Stomata and Guard Cells
     Stomata are tiny pores on the leaf surface that allow gas exchange. Guard cells are specialized kidney-shaped cells that flank each stoma and control its opening and closing.


  4. Difference between Grana and Stroma
     Grana are stacks of thylakoids in chloroplasts where light reactions take place. Stroma is the fluid-filled part of the chloroplast where the dark (light-independent) phase occurs.


  5. Difference between Chlorophyll and Chloroplast
     Chlorophyll is a green pigment that captures light energy. Chloroplast is a cell organelle containing chlorophyll and other components for photosynthesis.


  6. Difference between Photosynthesis and Respiration
     Photosynthesis is an anabolic, endothermic process in which plants make glucose and oxygen from carbon dioxide and water using sunlight. Respiration is a catabolic, exothermic process in which organisms break down glucose to release energy.


  7. Difference between Palisade cells and Spongy cells
     Palisade cells are tightly packed, columnar cells rich in chloroplasts for maximum light absorption. Spongy cells are loosely arranged with air spaces to facilitate gas exchange.


  8. Difference between Carbon Fixation and Photolysis
     Carbon fixation is the process of converting carbon dioxide into glucose during the dark phase. Photolysis is the splitting of water using light during the light phase, releasing oxygen.


  9. Difference between ATP and NADPH
     ATP is an energy-carrying molecule used in the dark phase. NADPH is a hydrogen carrier that supplies reducing power for converting CO₂ into glucose.


  10. Difference between Variegated Leaf and Green Leaf
     A variegated leaf has both green and non-green patches; only green areas can photosynthesize. A green leaf is fully covered with chlorophyll and performs photosynthesis throughout.


  11. Difference between Starch and Glucose
     Starch is an insoluble carbohydrate stored in plant parts. Glucose is a soluble sugar formed immediately during photosynthesis and used for energy or converted into starch.


  12. Difference between Xylem and Phloem
     Xylem conducts water and minerals from roots to leaves. Phloem transports food from leaves to all parts of the plant.


  13. Difference between Cuticle and Epidermis
     The cuticle is a waxy, non-cellular outer layer that prevents water loss. The epidermis is the outermost cellular layer of the leaf that provides protection.


  14. Difference between Iodine Test and Benedict’s Test
     Iodine test detects starch and gives a blue-black colour. Benedict’s test detects reducing sugars and gives a red or orange precipitate.


  15. Difference between Day and Night Stomatal Activity
     During the day, stomata open to allow CO₂ in for photosynthesis. At night, stomata close to prevent water loss as photosynthesis does not occur.


  16. Difference between Mesophyll and Veins
     Mesophyll is the photosynthetic tissue of the leaf composed of palisade and spongy cells. Veins consist of vascular tissues (xylem and phloem) that transport water and food.


  17. Difference between Light Energy and Chemical Energy
     Light energy comes from the sun and is captured by chlorophyll. Chemical energy is stored in the bonds of glucose molecules formed during photosynthesis.


  18. Difference between Boiling in Water and Boiling in Alcohol (in experiments)
     Boiling in water kills the leaf and softens it. Boiling in alcohol removes chlorophyll, making the leaf colourless for the iodine test.


  19. Difference between Oxygen in Photosynthesis and Oxygen in Respiration
     In photosynthesis, oxygen is released as a by-product of water photolysis. In respiration, oxygen is used to break down glucose to release energy.


  20. Difference between External and Internal Factors of Photosynthesis
     External factors include light intensity, CO₂ concentration, temperature, and water availability. Internal factors include chlorophyll content, protoplasmic condition, and leaf structure.

Assertion and Reason

  • A. Both Assertion and Reason are true, and Reason is the correct explanation.
  • B. Both Assertion and Reason are true, but Reason is not the correct explanation.
  • C. Assertion is true, but Reason is false.
  • D. Assertion is false, but Reason is true.
  1. Assertion: Chlorophyll is necessary for photosynthesis.
     Reason: It absorbs green light from sunlight.
     Answer: C


  2. Assertion: Photosynthesis takes place only in the green parts of the plant.
     Reason: Green parts contain chloroplasts.
     Answer: A


  3. Assertion: Photolysis occurs during the light-dependent phase.
     Reason: Light energy breaks water into hydrogen and oxygen.
     Answer: A


  4. Assertion: Glucose is formed during the light-dependent phase.
     Reason: Light is used to convert CO₂ into glucose.
     Answer: C


  5. Assertion: Leaves are thin and broad.
     Reason: This helps in easy transport of minerals.
     Answer: C


  6. Assertion: ATP is produced during the light reaction.
     Reason: ATP is synthesized using energy released from glucose breakdown.
     Answer: C


  7. Assertion: Carbon dioxide is essential for photosynthesis.
     Reason: CO₂ provides the carbon atoms for glucose.
     Answer: A


  8. Assertion: Guard cells open the stomata during the day.
     Reason: They become flaccid in sunlight.
     Answer: C


  9. Assertion: Starch is stored in leaves as a result of photosynthesis.
     Reason: Glucose produced is transported directly to roots.
     Answer: C


  10. Assertion: Oxygen is a by-product of photosynthesis.
     Reason: It is released during the photolysis of water.
     Answer: A


  11. Assertion: Photosynthesis is an anabolic process.
     Reason: Complex substances are broken down during this process.
     Answer: C


  12. Assertion: Light is essential for the dark phase.
     Reason: Dark phase occurs only at night.
     Answer: D


  13. Assertion: Water is absorbed by the roots and reaches leaves.
     Reason: Xylem tissue is responsible for water transport.
     Answer: A


  14. Assertion: The palisade layer contains fewer chloroplasts than the spongy layer.
     Reason: Spongy layer is more exposed to light.
     Answer: D


  15. Assertion: Chloroplasts are present in all plant cells.
     Reason: All plant cells perform photosynthesis.
     Answer: D


  16. Assertion: Plants appear green due to chlorophyll.
     Reason: Chlorophyll reflects green light.
     Answer: A


  17. Assertion: During photosynthesis, sunlight is converted into chemical energy.
     Reason: The energy is stored in the bonds of glucose.
     Answer: A


  18. Assertion: The stroma is the site of the light reaction.
     Reason: Stroma contains chlorophyll.
     Answer: C


  19. Assertion: Carbon fixation occurs in the dark phase.
     Reason: It requires enzymes, not light.
     Answer: A


  20. Assertion: Alcohol is used to test starch in a leaf.
     Reason: Alcohol removes starch from the leaf.
     Answer: C


  21. Assertion: KOH is used in photosynthesis experiments.
     Reason: KOH absorbs carbon dioxide.
     Answer: A


  22. Assertion: Stomata close at night.
     Reason: Guard cells become turgid in darkness.
     Answer: C


  23. Assertion: Photosynthesis occurs only in the presence of light.
     Reason: Light is required to split glucose molecules.
     Answer: C


  24. Assertion: Carbon dioxide is a limiting factor in photosynthesis.
     Reason: Increased CO₂ concentration increases photosynthesis rate up to a point.
     Answer: A


  25. Assertion: Plants need oxygen for photosynthesis.
     Reason: Oxygen is used to synthesize glucose.
     Answer: D


  26. Assertion: Destarching is necessary before testing for starch.
     Reason: It ensures no pre-existing starch is in the leaf.
     Answer: A


  27. Assertion: Light intensity affects the rate of photosynthesis.
     Reason: Light supplies energy for the process.
     Answer: A


  28. Assertion: Temperature has no effect on photosynthesis.
     Reason: Photosynthesis does not involve enzymes.
     Answer: D


  29. Assertion: All leaf cells perform photosynthesis.
     Reason: All cells contain chloroplasts.
     Answer: D


  30. Assertion: Water is a raw material of photosynthesis.
     Reason: It provides hydrogen during photolysis.
     Answer: A

True or False

  1. Photosynthesis takes place in the mitochondria.
     Answer: False


  2. Chlorophyll is essential for the process of photosynthesis.
     Answer: True


  3. Oxygen is a raw material for photosynthesis.
     Answer: False


  4. The light-dependent phase occurs in the stroma of the chloroplast.
     Answer: False


  5. ATP and NADPH are produced in the light reaction.
     Answer: True


  6. Glucose is produced during the light-dependent phase.
     Answer: False


  7. Carbon dioxide is fixed during the dark phase.
     Answer: True


  8. Chloroplast is a double membrane-bound organelle.
     Answer: True


  9. The palisade mesophyll contains the highest number of chloroplasts.
     Answer: True


  10. Starch is the soluble form in which plants transport carbohydrates.
     Answer: False


  11. Destarching is done by keeping the plant in sunlight for 48 hours.
     Answer: False


  12. The iodine test is used to detect the presence of starch in leaves.
     Answer: True


  13. Stomata are responsible for gas exchange in leaves.
     Answer: True


  14. Guard cells become flaccid in the presence of sunlight.
     Answer: False


  15. KOH is used to absorb carbon dioxide in experiments.
     Answer: True


  16. Water is not a raw material in photosynthesis.
     Answer: False


  17. Alcohol is used to remove starch from leaves.
     Answer: False


  18. Light energy is converted into chemical energy during photosynthesis.
     Answer: True


  19. NADPH is formed in the dark phase of photosynthesis.
     Answer: False


  20. Oxygen is released during the light-dependent phase.
     Answer: True


  21. The cuticle is a transparent layer that allows light penetration.
     Answer: True


  22. The spongy mesophyll has more chloroplasts than the palisade layer.
     Answer: False


  23. Sunlight is required directly in the light-independent phase.
     Answer: False


  24. Glucose formed in photosynthesis can be stored as starch.
     Answer: True


  25. Photosynthesis decreases with increase in carbon dioxide concentration beyond a certain limit.
     Answer: True


  26. The dark phase of photosynthesis can occur in complete darkness.
     Answer: False


  27. Blue and red lights are most effective for photosynthesis.
     Answer: True


  28. Chlorophyll reflects green light, which is why plants appear green.
     Answer: True


  29. Roots carry out photosynthesis in most plants.
     Answer: False


  30. The main source of oxygen in photosynthesis is carbon dioxide.
     Answer: False


  31. Glucose is an end product of photosynthesis.
     Answer: True


  32. The leaf arrangement in a plant helps prevent overlapping to maximize sunlight exposure.
     Answer: True


  33. Osmosis is involved in the opening of stomata.
     Answer: True


  34. Phloem transports water from roots to leaves.
     Answer: False


  35. All green plant cells perform photosynthesis.
     Answer: False


  36. The grana is the site of carbon fixation.
     Answer: False


  37. Photosynthesis is a catabolic process.
     Answer: False


  38. The sugar concentration theory explains the opening of stomata.
     Answer: True


  39. K⁺ ion movement is responsible for stomatal movement.
     Answer: True


  40. Photosynthesis contributes to the carbon cycle.
     Answer: True


  41. The chloroplast contains both grana and stroma.
     Answer: True


  42. Respiration and photosynthesis are opposite processes.
     Answer: True


  43. Chlorophyll is present only in guard cells.
     Answer: False


  44. A bell jar is used in an experiment to demonstrate the necessity of CO₂ in photosynthesis.
     Answer: True


  45. Glucose is directly tested with iodine solution.
     Answer: False


  46. The main vein of a leaf is called the midrib.
     Answer: True


  47. Oxygen released during photosynthesis is used in respiration by plants and animals.
     Answer: True


  48. Photosynthesis only benefits plants.
     Answer: False


  49. The light-independent phase is also called the Calvin cycle.
     Answer: True


  50. Light, CO₂, and water are all essential raw materials for photosynthesis.
     Answer: True

Long Answer Questions

  1. Define photosynthesis. Write its word equation and chemical equation.
     Answer: Photosynthesis is the process by which green plants synthesize food using carbon dioxide and water in the presence of sunlight and chlorophyll.
     Word Equation: Carbon dioxide + Water → Glucose + Oxygen
     Chemical Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂


  2. Describe the role of chlorophyll in photosynthesis.
     Answer: Chlorophyll is the green pigment present in chloroplasts. It absorbs light energy from the sun and converts it into chemical energy. This energy is used to split water molecules and drive the synthesis of glucose during photosynthesis.


  3. Explain the structure and function of stomata.
     Answer: Stomata are tiny pores mainly located on the lower surface of leaves. Each stoma is flanked by two kidney-shaped guard cells. They control the opening and closing of the stomatal pore. Stomata regulate the exchange of gases – carbon dioxide enters, and oxygen and water vapour exit through them.


  4. What is photolysis? Where does it occur and what are its products?
     Answer: Photolysis is the splitting of water molecules using light energy during the light-dependent phase of photosynthesis. It occurs in the grana of chloroplasts. Products: Oxygen, protons (H⁺ ions), and electrons.


  5. Explain the light-dependent phase of photosynthesis.
     Answer: The light-dependent phase takes place in the grana of chloroplasts. In this phase, light energy is absorbed by chlorophyll and used to split water (photolysis) into oxygen, hydrogen ions, and electrons. ATP and NADPH are formed, which store energy and reducing power for the dark phase.


  6. Describe the light-independent phase of photosynthesis.
     Answer: This phase occurs in the stroma of chloroplasts and does not require light. ATP and NADPH from the light-dependent phase are used to fix carbon dioxide into glucose. This cycle is enzymatic and forms part of the Calvin cycle.


  7. Why is photosynthesis considered an anabolic and endothermic process?
     Answer: Photosynthesis is anabolic because it builds complex glucose molecules from simple substances (CO₂ and H₂O). It is endothermic because it requires the absorption of light energy to drive the reactions.


  8. Give adaptations of leaves for photosynthesis.
     Answer: Large surface area to absorb more sunlight, leaf arrangement prevents overlapping, transparent cuticle and upper epidermis allow light penetration, numerous stomata facilitate gas exchange, thin leaves help gas diffusion, chloroplasts trap light, and extensive vein network aids transport.


  9. How do guard cells regulate the opening and closing of stomata?
     Answer: In sunlight, guard cells produce sugar, increasing osmotic pressure. Water enters by osmosis, making them turgid and opening the stoma. In darkness, sugar is used up, water exits, and guard cells become flaccid, closing the stoma.


  10. Describe the sugar concentration theory of stomatal movement.
     Answer: According to this theory, during the day, guard cells photosynthesize and accumulate sugar. This increases osmotic pressure, drawing water into the cells. Turgidity causes the guard cells to bulge outward, opening the stomatal pore.


  11. Describe the potassium ion (K⁺) theory of stomatal movement.
     Answer: Light activates proton pumps in guard cells, leading to the uptake of K⁺ ions. This increases the osmotic pressure, causing water to enter, and the guard cells become turgid, resulting in stomatal opening.


  12. What are the main factors affecting photosynthesis?
     Answer: External factors: Light intensity, carbon dioxide concentration, temperature, and water. Internal factors: Chlorophyll content, protoplasmic condition, and leaf structure.


  13. Write an experiment to show that CO₂ is necessary for photosynthesis.
     Answer: Place a de-starched plant in a bell jar. Keep one leaf inside a flask containing KOH to absorb CO₂ and another outside as a control. After exposure to sunlight, test both leaves with iodine. The leaf outside turns blue-black while the one inside does not, proving CO₂ is necessary.


  14. Describe an experiment to test the presence of starch in a leaf.
     Answer: Boil a leaf in water, then in alcohol to remove chlorophyll. Soften in warm water, then add iodine solution. Blue-black colour indicates presence of starch, confirming photosynthesis has occurred.


  15. What is destarching and why is it done before experiments?
     Answer: Destarching is the process of removing existing starch by keeping the plant in darkness for 48-72 hours. It ensures any starch detected is the result of the experiment.


  16. Explain the role of water in photosynthesis.
     Answer: Water supplies electrons and protons for the light reaction through photolysis. It also maintains cell turgidity and is essential for stomatal opening.


  17. What is the importance of photosynthesis in nature?
     Answer: Photosynthesis provides food, releases oxygen for respiration, balances atmospheric gases, and is fundamental to the carbon cycle and all life on Earth.


  18. Why is oxygen considered a by-product of photosynthesis?
     Answer: Oxygen is released during photolysis of water in the light-dependent phase. It is not used in glucose synthesis, thus considered a by-product.


  19. What happens to the glucose produced in photosynthesis?
     Answer: It is used for energy in respiration, stored as starch, or converted into other compounds like cellulose, fats, and proteins.


  20. What is the carbon cycle? Describe the role of photosynthesis in it.
     Answer: The carbon cycle is the movement of carbon among the atmosphere, organisms, and the Earth. Photosynthesis removes CO₂ from the air and incorporates it into organic compounds, forming the base of the food chain.


  21. Why is chlorophyll essential for photosynthesis?
     Answer: Chlorophyll absorbs sunlight and initiates the conversion of light energy into chemical energy needed for the synthesis of glucose.


  22. How does temperature affect the rate of photosynthesis?
     Answer: Enzymes control photosynthesis and work best within an optimum temperature range. Very low or very high temperatures slow or stop the process.


  23. What are the two phases of photosynthesis? Name their locations.
     Answer: The light-dependent phase (occurs in the grana) and the light-independent or dark phase (occurs in the stroma).


  24. What is the importance of ATP and NADPH in photosynthesis?
     Answer: ATP provides energy, and NADPH supplies reducing power to convert carbon dioxide into glucose in the dark phase.


  25. Why is sunlight necessary for photosynthesis?
     Answer: Sunlight activates chlorophyll, triggers photolysis of water, and facilitates the formation of ATP and NADPH.


  26. Explain the role of the leaf vein system in photosynthesis.
     Answer: Veins contain xylem and phloem. Xylem brings water and minerals to the leaf; phloem distributes glucose to other parts of the plant.


  27. State three differences between light and dark phases of photosynthesis.
     Answer: Light phase requires sunlight; dark phase does not. Light phase produces ATP and NADPH; dark phase uses them. Light phase occurs in grana; dark phase in stroma.


  28. Why is green light least effective in photosynthesis?
     Answer: Chlorophyll reflects green light instead of absorbing it, making it the least useful for photosynthesis.


  29. What is meant by the term ‘grana’?
     Answer: Grana are stacks of thylakoid membranes within chloroplasts where the light-dependent reactions occur.


  30. What is the function of the cuticle in a leaf?
     Answer: The cuticle is a waxy, transparent layer that reduces water loss and allows light penetration for photosynthesis.


  31. How do plants regulate CO₂ entry for photosynthesis?
     Answer: By opening and closing stomata through changes in the turgor pressure of guard cells.


  32. How does light intensity affect photosynthesis?
     Answer: Increasing light intensity increases the rate of photosynthesis up to a point, after which the rate plateaus due to other limiting factors.


  33. What is the role of enzymes in the dark phase?
     Answer: Enzymes in the stroma catalyze the chemical reactions that convert CO₂ into glucose using ATP and NADPH.


  34. Explain how photosynthesis contributes to the food chain.
     Answer: Photosynthesis produces glucose, which is the primary source of energy and organic material for all living organisms.


  35. Why is the upper epidermis of the leaf transparent?
     Answer: To allow sunlight to penetrate to the mesophyll cells where chloroplasts are present for photosynthesis.


  36. How does the arrangement of leaves help photosynthesis?
     Answer: Leaves are arranged to minimize overlapping and ensure each leaf receives maximum sunlight.


  37. What is meant by osmotic pressure in guard cells?
     Answer: Osmotic pressure is the tendency of guard cells to absorb water due to increased solute concentration, leading to stomatal opening.


  38. List any four structural features of a leaf that aid in photosynthesis.
     Answer: Large surface area, numerous stomata, presence of chloroplasts, thinness for quick diffusion of gases.


  39. How is excess glucose stored in plants?
     Answer: Excess glucose is converted into starch and stored in leaves, roots, or other storage organs.


  40. Differentiate between autotrophs and heterotrophs.
     Answer: Autotrophs prepare their own food from inorganic substances (e.g., green plants). Heterotrophs depend on other organisms for food (e.g., animals).


  41. Explain the importance of NADPH in photosynthesis.
     Answer: NADPH provides the hydrogen ions required to reduce carbon dioxide to glucose in the light-independent phase.


  42. What is the significance of the palisade layer in photosynthesis?
     Answer: It contains the highest number of chloroplasts and is directly exposed to light, making it the main site for photosynthesis.


  43. What role do mesophyll cells play in photosynthesis?
     Answer: They house chloroplasts and are the principal site for photosynthetic activity within the leaf.


  44. How is the presence of CO₂ proved essential for photosynthesis?
     Answer: By using a setup with KOH to absorb CO₂, showing that no starch is formed in its absence (no blue-black colour with iodine).


  45. What is the function of the epidermis in a leaf?
     Answer: The epidermis protects internal tissues, prevents water loss, and allows light to reach mesophyll cells.


  46. How does water scarcity affect photosynthesis?
     Answer: Stomata close to prevent water loss, reducing CO₂ intake and thus lowering photosynthesis.


  47. Why is it necessary to boil the leaf in alcohol during the starch test?
     Answer: To remove chlorophyll so that colour changes with iodine are visible clearly.


  48. Describe the role of sunlight in the carbon cycle.
     Answer: Sunlight enables photosynthesis, which removes atmospheric CO₂ and converts it into organic food for living organisms.


  49. How does the structure of chloroplast help in photosynthesis?
     Answer: The grana capture light for the light reaction; the stroma contains enzymes for the dark phase, allowing compartmentalization of tasks.


  50. Why is it important to maintain a balance between photosynthesis and respiration?
     Answer: To ensure a stable level of oxygen and carbon dioxide in the atmosphere, supporting life processes.

Give Reasons

  1. Give reason: Leaves are green in colour.
     Answer: Due to the presence of chlorophyll, which reflects green light.


  2. Give reason: Photosynthesis does not occur at night.
     Answer: Sunlight, which is essential for the light-dependent phase, is absent at night.


  3. Give reason: Oxygen is considered a by-product of photosynthesis.
     Answer: Because it is released during photolysis and is not used in glucose formation.


  4. Give reason: Chlorophyll is essential for photosynthesis.
     Answer: It absorbs sunlight to drive the light-dependent reactions.


  5. Give reason: A destarched plant is used for photosynthesis experiments.
     Answer: To ensure that any starch formed is due to the experiment and not pre-existing.


  6. Give reason: A leaf is boiled in alcohol during starch test.
     Answer: To remove chlorophyll so that colour change with iodine is clearly visible.


  7. Give reason: KOH is placed in the bell jar during an experiment.
     Answer: To absorb carbon dioxide and show that CO₂ is essential for photosynthesis.


  8. Give reason: The palisade layer contains the most chloroplasts.
     Answer: Because it receives maximum sunlight, making it the main site of photosynthesis.


  9. Give reason: Glucose is stored as starch in plants.
     Answer: Because starch is insoluble and suitable for storage.


  10. Give reason: Photosynthesis is called an anabolic process.
     Answer: Because it builds complex glucose molecules from simpler ones.


  11. Give reason: Photosynthesis is called an endothermic process.
     Answer: Because it requires the absorption of solar energy.


  12. Give reason: Water is essential for photosynthesis.
     Answer: It provides hydrogen ions through photolysis and maintains cell turgidity.


  13. Give reason: Stomata open during the day and close at night.
     Answer: Light activates guard cells, causing them to become turgid and open the stomata.


  14. Give reason: Green light is least effective for photosynthesis.
     Answer: Because it is reflected, not absorbed, by chlorophyll.


  15. Give reason: The dark phase is called “light-independent”.
     Answer: Because it does not require direct light and uses ATP and NADPH from the light phase.


  16. Give reason: Leaf arrangement helps in efficient photosynthesis.
     Answer: It ensures maximum light exposure by preventing overlapping.


  17. Give reason: The cuticle and upper epidermis are transparent.
     Answer: To allow light to pass through to the photosynthetic cells.


  18. Give reason: Stomata are mostly on the lower leaf surface.
     Answer: To reduce water loss due to lesser exposure to sunlight.


  19. Give reason: The mesophyll is divided into palisade and spongy layers.
     Answer: To maximize light absorption and facilitate gas exchange.


  20. Give reason: Photosynthesis helps regulate atmospheric CO₂ levels.
     Answer: Because it absorbs CO₂ and converts it into glucose.


  21. Give reason: The plant appears wilted during water shortage.
     Answer: Guard cells lose turgidity, closing stomata and slowing photosynthesis.


  22. Give reason: Glucose is not directly transported in plants.
     Answer: Because it is reactive and soluble; it’s converted into sucrose for transport.


  23. Give reason: Veins in the leaf are essential for photosynthesis.
     Answer: They transport water (xylem) and carry food away (phloem).


  24. Give reason: Light intensity affects the rate of photosynthesis.
     Answer: Higher light increases energy availability, boosting the light reactions.


  25. Give reason: High temperature may reduce the rate of photosynthesis.
     Answer: Because enzymes involved can denature at high temperatures.


  26. Give reason: The stroma is important for photosynthesis.
     Answer: It contains enzymes for the dark phase of photosynthesis.


  27. Give reason: Carbon fixation occurs in the stroma.
     Answer: Because it houses the Calvin cycle enzymes that convert CO₂ to glucose.


  28. Give reason: ATP is called the energy currency of the cell.
     Answer: Because it stores and provides energy for various cellular processes.


  29. Give reason: NADPH is required in the dark phase.
     Answer: It supplies hydrogen for the reduction of CO₂ to form glucose.


  30. Give reason: Blue and red light are best for photosynthesis.
     Answer: Because chlorophyll absorbs them most efficiently.


  31. Give reason: Destarching a plant requires placing it in the dark.
     Answer: So it uses up all its stored starch in respiration.


  32. Give reason: Boiling in alcohol is done in a water bath.
     Answer: Because alcohol is highly flammable and direct heating is unsafe.


  33. Give reason: Alcohol-treated leaves become brittle.
     Answer: Because alcohol removes chlorophyll and dehydrates the leaf.


  34. Give reason: Plants with variegated leaves show starch only in green areas.
     Answer: Because only green areas contain chlorophyll and perform photosynthesis.


  35. Give reason: Glucose formed in photosynthesis is quickly used or stored.
     Answer: To prevent its accumulation and to provide energy or form starch.


  36. Give reason: Photosynthesis is essential for all living organisms.
     Answer: It provides food and oxygen, supporting life on Earth.


  37. Give reason: The carbon cycle would break without photosynthesis.
     Answer: Because CO₂ would not be removed from the atmosphere and converted into organic matter.


  38. Give reason: Plants are called autotrophs.
     Answer: Because they make their own food using sunlight, CO₂, and water.


  39. Give reason: Chloroplasts are found only in green parts of the plant.
     Answer: Because these parts need to carry out photosynthesis.


  40. Give reason: Photolysis is important in photosynthesis.
     Answer: It produces oxygen and provides hydrogen for glucose formation.


  41. Give reason: Plants kept in green light show poor growth.
     Answer: Because chlorophyll does not absorb green light effectively.


  42. Give reason: A leaf is boiled before adding iodine solution.
     Answer: To kill cells and stop all metabolic activities for accurate testing.


  43. Give reason: Epidermal cells lack chloroplasts.
     Answer: Their function is protection, not photosynthesis.


  44. Give reason: Oxygen release is proof of photosynthesis.
     Answer: Because oxygen is a by-product of the photolysis of water.


  45. Give reason: Stomata are essential for gaseous exchange.
     Answer: They allow CO₂ to enter and O₂ to exit the leaf.


  46. Give reason: ATP and NADPH are called assimilatory power.
     Answer: Because they help in assimilation of CO₂ into glucose.


  47. Give reason: Palisade layer is directly below the upper epidermis.
     Answer: To receive the maximum amount of sunlight.


  48. Give reason: Transpiration helps in photosynthesis.
     Answer: It aids in the upward movement of water to the leaves.


  49. Give reason: Respiration and photosynthesis are interdependent.
     Answer: Photosynthesis produces oxygen and glucose needed in respiration; respiration provides CO₂ for photosynthesis.


  50. Give reason: Photosynthesis is more efficient in bright sunlight.
     Answer: Because more light increases the rate of the light-dependent reactions.

Arrange the Words 

Case Studies

Case Study 1:
 Ravi kept a potted plant in darkness for 72 hours and then exposed it to sunlight for 6 hours. He performed the iodine test on one leaf and found it turned blue-black.
 Question: Why was the leaf kept in darkness before sunlight exposure?
 Answer: To destarch the leaf and ensure that starch formed is only due to the current photosynthesis.

 

Case Study 2:
 A student covers part of a leaf with black paper and keeps the plant in sunlight. Later, he tests the leaf with iodine.
 Question: What will be the observation, and what does it prove?
 Answer: The uncovered part turns blue-black, and the covered part doesn’t. This proves that light is necessary for photosynthesis.

 

Case Study 3:
 In an experiment, a plant was placed inside a bell jar with KOH and exposed to sunlight. Leaves did not turn blue-black in iodine test.
 Question: Why did the leaves fail to turn blue-black?
 Answer: KOH absorbed CO₂, which is essential for photosynthesis; hence no starch was formed.

 

Case Study 4:
 Shweta tested two leaves – one green and one yellow – from a variegated plant after exposure to sunlight.
 Question: Which leaf showed positive iodine test and why?
 Answer: The green part of the leaf turned blue-black because chlorophyll is necessary for photosynthesis.

 

Case Study 5:
 During an experiment, a leaf was boiled in water, then in alcohol, and finally tested with iodine.
 Question: Why was the alcohol step necessary?
 Answer: To remove chlorophyll and allow iodine to show colour change clearly.

 

Case Study 6:
 A leaf from a well-watered plant is tested for starch and shows blue-black colour.
 Question: What does this result indicate about the plant’s activity?
 Answer: Photosynthesis occurred, resulting in starch formation.

 

Case Study 7:
 Rohan noticed that plants in a shaded garden grew slower than those in full sunlight.
 Question: What could be the reason?
 Answer: Less light reduces the rate of photosynthesis, hence slower growth.

 

Case Study 8:
 A plant kept in green light showed little to no starch production.
 Question: Why was starch not formed?
 Answer: Chlorophyll reflects green light, making it least effective for photosynthesis.

 

Case Study 9:
 A student observes bubbles coming from the stem of an aquatic plant in sunlight.
 Question: What gas is being released and what does it indicate?
 Answer: Oxygen; it indicates active photosynthesis.

 

Case Study 10:
 After an experiment, a student concludes that water is not required for photosynthesis.
 Question: Is this conclusion correct? Justify.
 Answer: No. Water is essential as it provides hydrogen for glucose and releases oxygen via photolysis.

 

Case Study 11:
 A leaf was tested immediately after removing the plant from darkness. No blue-black colour was observed.
 Question: What does this imply?
 Answer: No starch was present as the plant had not undergone photosynthesis recently.

 

Case Study 12:
 A plant in a terrarium was sealed and placed in sunlight. After a day, condensation formed and oxygen content increased.
 Question: What does this show?
 Answer: Photosynthesis occurred – water vapour and oxygen are products.

 

Case Study 13:
 A teacher asks: “Why does a plant close its stomata during water scarcity?”
 Question: What should be the student’s reply?
 Answer: To reduce water loss by transpiration and conserve internal moisture.

 

Case Study 14:
 A leaf turned blue-black in starch test only in patches.
 Question: What could be the reason for this uneven starch distribution?
 Answer: Unequal exposure to light or variation in chlorophyll presence (e.g., variegated leaf).

 

Case Study 15:
 A sealed jar contains a candle and a plant. The candle burns longer when the plant is exposed to sunlight first.
 Question: Why does this happen?
 Answer: The plant releases oxygen through photosynthesis, allowing the candle to burn longer.

 

Case Study 16:
 A student says, “Photosynthesis continues even at night.”
 Question: Is this statement correct? Explain.
 Answer: No. Light-dependent reactions require sunlight, so photosynthesis does not occur at night.

 

Case Study 17:
 A plant placed near a window grows toward the light.
 Question: How is this related to photosynthesis?
 Answer: The plant orients itself to maximize light absorption for photosynthesis (phototropism).

 

Case Study 18:
 In a sealed setup with aquatic plant and bromothymol blue, the solution turns from yellow to blue under sunlight.
 Question: What does the colour change indicate?
 Answer: CO₂ was used in photosynthesis, reducing acidity; hence pH increased turning it blue.

 

Case Study 19:
 A student finds that a boiled leaf doesn’t change colour with iodine.
 Question: Why did the iodine test fail?
 Answer: Boiling damages cells and stops reactions, preventing starch detection.

 

Case Study 20:
 An experiment shows increased photosynthesis rate with rising light intensity until it levels off.
 Question: Why doesn’t the rate continue increasing?
 Answer: After a point, other factors like CO₂ concentration or temperature become limiting.

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