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Quiz Chapter 2: Leaf Structure and Function

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

10 questions · plays in fullscreen

Full Question List & Answer Key

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

1. How does the thinness of a leaf lamina adapt it for efficient photosynthesis?

  1. It increases mechanical resistance against strong wind gusts.
  2. It shortens the diffusion distance for gases like CO2 to reach inner mesophyll cells.
  3. It prevents water loss completely without requiring a waxy cuticle.
  4. It allows phloem to transport minerals without expenditure of ATP.
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Answer: B

A thin lamina minimizes internal diffusion path distances for carbon dioxide and oxygen between stomata and photosynthetic cells.

2. 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.

3. What structural feature of thylakoids inside chloroplasts increases light absorption efficiency?

  1. Their arrangement into stacked structures called grana
  2. Thick lignified secondary cell wall reinforcements
  3. Large central water vacuoles inside each disc
  4. Presence of perforated sieve plates across their membranes
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Answer: A

Thylakoids are organized into stacks called grana, significantly increasing total membrane surface area for chlorophyll pigment anchoring.

4. 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.

5. Which environmental condition results in the LOWEST rate of transpiration?

  1. High light intensity, warm temperature, low humidity, strong wind
  2. Low light intensity, cold temperature, high air humidity, calm air
  3. High light intensity, hot temperature, dry air, moderate wind
  4. Moderate light intensity, warm temperature, low air humidity, breezy air
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Answer: B

Transpiration slows down in low light (stomata closed), low temperature (less kinetic energy), high humidity (narrow vapor gradient), and calm air.

6. What is the spatial orientation of xylem and phloem inside a leaf vascular bundle?

  1. Xylem is located on the upper side; phloem is located on the lower side.
  2. Phloem is located on the upper side; xylem is located on the lower side.
  3. Xylem forms a central core entirely surrounded by phloem rings.
  4. Xylem and phloem are arranged in alternating concentric circles.
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Answer: A

In leaf vascular bundles (veins), xylem tissue faces toward the upper surface while phloem tissue faces toward the lower surface.

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 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.

9. 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.

10. What primary physiological event initiates stomatal opening in guard cells during daylight?

  1. Passive loss of water to surrounding cells
  2. Active transport of potassium ions (K+) into guard cells
  3. Accumulation of abscisic acid (ABA) within the vacuole
  4. Efflux of sucrose out of guard cell cytoplasm
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Answer: B

In daylight, active transport pumps K+ ions into guard cells, lowering their solute potential and driving osmotic influx of water to increase turgidity.

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