[Turn over

For

Examiner's

Use

4 (a) Complete the balanced chemical equation for photosynthesis.

light

+ + [3]

chlorophyll A student investigated the effect of increasing the concentration of carbon dioxide on the

rate of photosynthesis of Cabomba, an aquatic plant. Fig. 4.1 shows the apparatus that the student used.

gas bubblesyringelamp

ruler

plastic tubing

meniscus

capillary tubing

sodium hydrogencarbonate(NaHCO3) solution

Cabomba

Fig. 4.1 The concentration of carbon dioxide in the water surrounding the plant was changed by

adding different concentrations of sodium hydrogencarbonate solution to the water. The student recorded the time taken for the meniscus to travel 50 mm down the tubing. The rate of photosynthesis was calculated as: rate of photosynthesis = 1000 t where t = time taken in seconds for the meniscus to travel 50 mm.

Q1

For

Examiner's

Use

The student’s results are shown in Table 4.1.

Table 4.1

concentration of sodium hydrogencarbonate

solution / mol per dm3

t, time taken for meniscus to travel 50 mm / s

rate of photosynthesis (1000/t)

0.00 4998 0.20

0.01 2500 0.40

0.02 1175 0.85

0.05 350 2.86

0.07 201

0.10 199 5.03

(b) Calculate the rate of photosynthesis for the concentration of sodium

hydrogencarbonate solution of 0.07 mol per dm3. Write your answer in Table 4.1. [1] (c) (i) Explain why the lamp must be kept at a fixed distance from the syringe.

[2]

(ii) Explain what caused the meniscus to move down the capillary tubing.

[2]

15

For

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(d) Fig. 4.2 is a partially completed graph of the student’s results. Complete the graph by labelling the axes, adding the missing point and drawing a

suitable line.

6.0

5.0

4.0

3.0

2.0

1.0

0.00.04 0.06 0.08 0.10

..............................

..............................

..................................................

0.00 0.02

Fig. 4.2

[3]

For

Examiner's

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(e) Explain, using the term limiting factors, the effect of carbon dioxide concentration on the rate of photosynthesis as shown by the student’s results.

You will gain credit for using the data in the table and the graph to answer the question.

[5]

[Total: 16]

The image below shows some cells on the lower surface of a leaf.

                                                        © Stefan Diller/Science Photo Library

(a)     What are the cells labelled X called?

Draw a ring around the correct answer.

guard cells                palisade cells                mesophyll cells (1)

(b)     Water loss by evaporation from leaves is called transpiration.

A student set up an experiment to investigate water loss from leaves.

The student:

•        took two leaves, A and B, from a plant

•        put Vaseline (grease) on both sides of Leaf B; did nothing to Leaf A

•        wrote down the mass of each leaf

•        attached the leaves onto a string as shown in the diagram below.

Q2

 Leaf A

(no treatment) Leaf B

(both surfaces covered in Vaseline)

•        left the leaves for 48 hours

•        wrote down the mass of each leaf again

•        calculated the percentage (%) change in mass for each leaf.

(i)      Give one variable that the student controlled in this investigation.

...............................................................................................................

............................................................................................................... (1)

(ii)     The mass of Leaf A was 1.60 g at the start of the investigation. After 48 hours it was 1.28 g.

Calculate the % decrease in mass over 48 hours.

...............................................................................................................

...............................................................................................................

% decrease = ..................................... (2)

(c)     Vaseline blocks the stomata.

The % change in mass of Leaf B was less than Leaf A after 48 hours. Explain why.

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........................................................................................................................

........................................................................................................................ (1)

(d)     Give three environmental conditions that would increase transpiration.

1 ......................................................................................................................

2 ......................................................................................................................

3 ...................................................................................................................... (3)

(Total 8 marks)

The diagram below shows a cross-section of a plant root. The transport tissues are labelled.

(a)     (i)      What is tissue A?

Draw a ring around the correct answer.

cuticle                epidermis                xylem (1)

(ii)     Name two substances transported by tissue A.

1 .............................................................................................................

2 ............................................................................................................. (2)

(b)     Phloem is involved in a process called translocation.

(i)      What is translocation?

...............................................................................................................

...............................................................................................................

............................................................................................................... (1)

(ii)     Explain why translocation is important to plants.

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...............................................................................................................

............................................................................................................... (2)

Q3

(c)     Plants must use active transport to move some substances from the soil into root hair cells.

(i)      Active transport needs energy.

Which part of the cell releases most of this energy?

Tick (✓) one box.

(1)

 mitochondria  

 nucleus  

  ribosome  

(ii)     Explain why active transport is necessary in root hair cells.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

............................................................................................................... (2)

(Total 9 marks)

Plants exchange substances with the environment.

(a)     Plant roots absorb water mainly by osmosis. Plant roots absorb ions mainly by active transport.

Explain why roots need to use the two different methods to absorb water and ions.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

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............................................................................................................... (4)

Q4

(b)     What is meant by the transpiration stream?

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...............................................................................................................

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...............................................................................................................

............................................................................................................... (3)

(c)     Students investigated the loss of water vapour from leaves.

The students:

•        cut some leaves off a plant

•         measured the mass of these leaves every 30 minutes for 180 minutes.

The graph shows the students’ results.

 

(i)      The rate of mass loss in the first 30 minutes was 7 milligrams per gram of leaf per minute.

Calculate the rate of mass loss between 30 minutes and 180 minutes.

...............................................................................................................

...............................................................................................................

Rate of mass loss = .............................. milligrams per gram of leaf per minute (2)

(ii)     The rate of mass loss between 0 and 30 minutes was very different from the rate of mass loss between 30 and 180 minutes.

Suggest an explanation for the difference between the two rates.

...............................................................................................................

...............................................................................................................

...............................................................................................................

............................................................................................................... (2)

(Total 11 marks)

Q4.          The photograph shows part of the surface of a plant root. This part of the root is covered with hundreds of structures like the one labelled X.

                 

(a)     What is the name of structure X?

          Draw a ring around one answer.

                     root hair                      stoma                        villus (1)

(b)     (i)      Use the scale to measure the length Y–Z on the photograph.

         On the photograph, length Y–Z = .................................... mm. (1)

Q5

(ii)     The photograph shows the root magnified 100 times.

         Calculate the actual length Y–Z.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Actual length Y–Z = ........................................mm. (2)

(iii)     Structure X is very small. There are thousands of structures like X on a plant root.

         How does this help the plant?

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(Total 6 marks)