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Biology questions, chapter 2
Nama / NameKelas / ClassTarikh / Date

Leaf Structure and Function

43 marks. Use Practice to check each answer as you go, or Exam to answer everything against the clock first.

Section A: objective questions

12 marks
Choose the best answer for each question.
1

Question 1

Which part of the leaf connects the lamina to the stem?
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A
The petiole is the leaf stalk that joins the lamina to the stem (p. 28).
For the teacher: Remembering, low difficulty, standard 2.1
Textbook p. 28
2

Question 2

Which layer of the leaf lamina contains the most chloroplasts and is the main site of photosynthesis?
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C
Palisade mesophyll cells are tall, closely packed and full of chloroplasts (p. 30).
For the teacher: Remembering, low difficulty, standard 2.1
Textbook p. 30
3

Question 3

In the morning, sucrose builds up in the guard cells. What happens next?
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C
More sucrose lowers the water potential, so water enters by osmosis. The guard cells become turgid and curve, opening the stoma (p. 32).
For the teacher: Understanding, medium difficulty, standard 2.2
Textbook p. 32
4

Question 4

About what percentage of transpiration takes place through the stomata of the leaves?
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D
About 90% of the water vapour lost leaves through the stomata (p. 36).
For the teacher: Remembering, low difficulty, standard 2.3
Textbook p. 36
5

Question 5

A potometer air bubble moves 3.6 cm in 12 minutes. What is the rate of water uptake?
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A
Rate = distance ÷ time = 3.6 ÷ 12 = 0.30 cm/min.
For the teacher: Applying, medium difficulty, standard 2.3
Textbook p. 38
6

Question 6

Which condition gives the highest rate of transpiration?
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B
Higher temperature, lower humidity and faster air movement each increase transpiration (p. 37).
For the teacher: Understanding, low difficulty, standard 2.3
Textbook p. 37
7

Question 7

Diagram 1 shows a chloroplast. In which part does the light-independent reaction take place?
Chloroplast showing thylakoids stacked as grana inside a fluid
Diagram 1
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D
The light-independent reaction takes place in the stroma, the colourless fluid around the grana (p. 42). The light-dependent reaction is in the thylakoids.
For the teacher: Remembering, low difficulty, standard 2.4
Textbook p. 42
8

Question 8

What is the role of photolysis in photosynthesis?
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D
Photolysis splits water in the light, giving electrons to chlorophyll, H⁺ to NADP⁺ and releasing oxygen (p. 44).
For the teacher: Understanding, low difficulty, standard 2.4
Textbook p. 44
9

Question 9

In paper chromatography a pigment moved 3.5 cm and the solvent moved 7.0 cm. What is the Rf value, and which pigment is it?
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A
Rf = 3.5 ÷ 7.0 = 0.50, which is chlorophyll b (Table 2.3, p. 43).
For the teacher: Applying, medium difficulty, standard 2.4
Textbook p. 43
10

Question 10

Diagram 2 shows the rate of photosynthesis against light intensity for two carbon dioxide concentrations, X (lower) and Y (higher). Why does graph X become level at P?
Two graphs of rate of photosynthesis against light intensity; X levels off earlier and lower than Y
Diagram 2
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B
At P, more light does not help because there is too little CO₂. Graph Y has more CO₂, so it keeps rising to a higher level (p. 46).
For the teacher: Analysing, high difficulty, standard 2.4
Textbook p. 46
11

Question 11

A leaf looks green because chlorophyll mostly
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B
Chlorophyll absorbs mainly red and blue light and reflects green light (p. 51).
For the teacher: Understanding, low difficulty, standard 2.4
Textbook p. 51
12

Question 12

At the compensation point of a plant,
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C
Compensation point is the light intensity at which the rate of photosynthesis equals the rate of respiration (p. 52).
For the teacher: Understanding, low difficulty, standard 2.5
Textbook p. 52

Section B: structured questions

31 marks
Answer all questions.
13

Question 13

Diagram 3 shows a cross-section of a leaf lamina.
Cross-section of a leaf lamina with the layers labelled
Diagram 3
[1 mark] (a)Name the layer of tall cells arranged closely and vertically beneath the upper epidermis.
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Tick each point you got.
[1 mark] (b)Explain why the cuticle is transparent.
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[2 marks] (c)State the function of the xylem and the phloem in the leaf.
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For the teacher: Understanding, low difficulty, standard 2.1
Textbook p. 29
14

Question 14

A plant is left without water for three days. Its leaves wilt and the stomata close.
[1 mark] (a)State the condition of the guard cells when the stomata are closed.
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[3 marks] (b)Explain why the guard cells change shape when the plant has enough water.
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[1 mark] (c)Why is it an advantage to the plant that the stomata close?
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For the teacher: Understanding, medium difficulty, standard 2.2
Textbook p. 35
15

Question 15

A student used a potometer to compare the transpiration of a leafy twig in two conditions. The air bubble moved the distances shown in 10 minutes.
ConditionDistance moved (cm)
Still air2.0
In front of a fan5.5
[2 marks] (a)Calculate the rate of transpiration in front of the fan.
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[2 marks] (b)Explain the difference between the two results.
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[1 mark] (c)Why must the twig be cut under water?
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For the teacher: Applying, medium difficulty, standard 2.3
Textbook p. 38
16

Question 16

Diagram 4 shows how the rate of photosynthesis of a plant changes with temperature.
Graph of rate of photosynthesis against temperature rising to a maximum at 30 degrees then falling to zero at 45 degrees
Diagram 4
[1 mark] (a)State the optimum temperature shown on the graph.
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[2 marks] (b)Explain why the rate increases from 0 °C to 30 °C.
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[1 mark] (c)Explain why the rate falls to zero at 45 °C.
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For the teacher: Analysing, high difficulty, standard 2.4
Textbook p. 47
17

Question 17

Photosynthesis has a light-dependent reaction and a light-independent reaction.
[2 marks] (a)In which part of the chloroplast does each reaction take place?
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[2 marks] (b)Name two substances from the light-dependent reaction that are used in the light-independent reaction.
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For the teacher: Remembering, low difficulty, standard 2.4
Textbook p. 44
18

Question 18

A fern on the rainforest floor has its compensation point at 10.00 am. A tall ficus tree in the same forest receives much more light.
[1 mark] (a)What is meant by compensation point?
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[2 marks] (b)Predict whether the ficus reaches its compensation point earlier or later than 10.00 am. Explain.
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[2 marks] (c)State the effect on the plant if it stayed at its compensation point every day.
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For the teacher: Evaluating, medium difficulty, standard 2.5
Textbook p. 53
19

Question 19

Complete the comparison of photosynthesis and respiration in plants.
[1 mark] (a)Which process takes place only in cells that contain chlorophyll?
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Photosynthesis
[1 mark] (b)Which process takes place in the mitochondria?
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Respiration
[1 mark] (c)Which process needs light?
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Photosynthesis
[1 mark] (d)Which process breaks down glucose to release energy?
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Respiration
For the teacher: Understanding, low difficulty, standard 2.5
Textbook p. 53