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Quiz Chapter 2: Leaf Structure and Function

10 questions ยท Form 5 Biology Bab 2: Leaf Structure and Function

Question 1 of 10Score: 0

Where do light-dependent reactions of photosynthesis specifically take place inside the chloroplast?

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. Where do light-dependent reactions of photosynthesis specifically take place inside the chloroplast?

  1. Stroma matrix
  2. Thylakoid membrane
  3. Outer chloroplast membrane
  4. Intermembrane space
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Answer: B

Light-dependent reactions occur within thylakoid membranes, which contain chlorophyll pigments and electron transport chains.

2. What chemical products generated during the light-dependent stage are required to drive the Calvin cycle in the stroma?

  1. Oxygen and glucose
  2. ATP and NADPH
  3. Water and carbon dioxide
  4. RuBP and RuBisCO
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Answer: B

ATP (energy source) and NADPH (reducing power) produced during light-dependent reactions drive carbon reduction in the light-independent Calvin cycle.

3. Which structural feature of guard cells causes them to curve outward when turgid, opening the stoma?

  1. Outer cell walls are thicker and less elastic than inner cell walls.
  2. Inner cell walls facing the pore are thicker and less flexible than outer walls.
  3. Guard cells lack cell walls entirely on their lateral surfaces.
  4. Chloroplasts exert mechanical outward push against cell membranes.
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Answer: B

The uneven thickness of guard cell walls (thick inner wall vs. thin flexible outer wall) forces them to bow outward when expanding with water.

4. What happens to a plant when environmental light intensity remains below its compensation point for an extended period?

  1. Glucose accumulation increases rapidly.
  2. Rate of photosynthesis exceeds cellular respiration.
  3. Stored organic reserves are depleted, leading to eventual plant death.
  4. Stomata remain permanently open to absorb excess oxygen.
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Answer: C

Below the compensation point, respiration breaks down organic molecules faster than photosynthesis produces them, depleting energy reserves.

5. Which leaf tissue features loose arrangement with large intercellular air spaces to facilitate gas diffusion?

  1. Palisade mesophyll
  2. Cuticle layer
  3. Spongy mesophyll
  4. Xylem vessels
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Answer: C

Spongy mesophyll cells are loosely arranged with abundant air spaces to allow carbon dioxide and oxygen to diffuse freely inside the leaf.

6. What is the primary role of photolysis of water during the light-dependent phase of photosynthesis?

  1. Directly fixing carbon dioxide into triose phosphate
  2. Replacing lost electrons in chlorophyll and releasing hydrogen ions (H+) and oxygen gas
  3. Actively pumping potassium ions across guard cell membranes
  4. Regenerating Ribulose 1,5-bisphosphate (RuBP)
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Answer: B

Photolysis splits H2O molecules using light energy to replace excited electrons in chlorophyll, yielding H+ ions for NADP+ reduction and releasing O2.

7. Why is the upper epidermal layer of a leaf transparent?

  1. To reflect excess ultraviolet radiation away from mesophyll cells
  2. To allow light to pass directly into the underlying photosynthetic mesophyll cells
  3. To encourage direct absorption of liquid water through stomatal pores
  4. To store excess starch grains produced during light reactions
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Answer: B

Upper epidermal cells lack chloroplasts and are clear, allowing maximum sunlight penetration into the palisade mesophyll.

8. Which leaf tissue layer contains the highest density of chloroplasts specialized for maximum sunlight absorption?

  1. Spongy mesophyll
  2. Palisade mesophyll
  3. Upper epidermis
  4. Vascular bundle
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Answer: B

Palisade mesophyll cells are vertically elongated, closely packed, and packed with chloroplasts to maximize photosynthetic light capture.

9. Which combination of factors causes guard cells to lose turgidity and become flaccid at night?

  1. Accumulation of K+ ions and osmotic entry of water
  2. Outflow of K+ ions, increasing water potential, and osmotic loss of water
  3. High rates of photolysis generating ATP inside guard cells
  4. Increased active pumping of protons into guard cell vacuoles
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Answer: B

At night, K+ ions leave guard cells, raising internal water potential and causing water to move out via osmosis, making guard cells flaccid.

10. What molecule acts as the final electron acceptor in the light-dependent stage, forming NADPH?

  1. Water (H2O)
  2. Carbon dioxide (CO2)
  3. NADP+
  4. Oxygen (O2)
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Answer: C

NADP+ accepts electrons and hydrogen ions at the end of the electron transport chain in thylakoids to form NADPH.

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