Photosynthesis Practice Questions

Question 1

3 marks

This question is about the photosynthesis reaction.

(a)

Complete the balanced symbol equation for photosynthesis.

$6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{\_\_\_\_\_\_\_\_} + \text{\_\_\_\_\_\_\_\_}$

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(b)

Photosynthesis is an endothermic reaction.

What is meant by an endothermic reaction?

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Question 2

4 marks

A gardener grows potato plants. The plants make glucose by photosynthesis.

(a)

Give two uses of the glucose made by photosynthesis in a plant, other than for respiration.

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(b)

The plants also absorb nitrate ions from the soil.

Explain why the plants need nitrate ions.

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Question 3

4 marks

Two students investigated photosynthesis using pieces of pondweed in test tubes of water.

(a)

Student A counted the bubbles of gas released by her pondweed. She counted 96 bubbles in 4 minutes.

Calculate the rate of photosynthesis in bubbles per minute.

Rate = __________ bubbles per minute

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(b)

Student B collected the gas from his pondweed in a measuring cylinder. He collected $4.8\ \text{cm}^3$ of gas in 20 minutes.

Calculate the rate of photosynthesis in $\text{cm}^3$ per hour.

Rate = __________ $\text{cm}^3$ per hour

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Question 4

3 marks

A scientist measured the rate of photosynthesis of a water plant at different light intensities. The temperature and the carbon dioxide concentration were kept constant.

The results are shown in the table.

Light intensity in arbitrary units	Rate of photosynthesis in $\text{cm}^3$ oxygen per hour
0	0
2	12
4	24
6	33
8	36
10	36

(a)

Describe the effect of light intensity on the rate of photosynthesis shown in the table.

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(b)

Suggest why the rate of photosynthesis did not increase between 8 and 10 arbitrary units of light intensity.

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Question 0

6 marks

A student was asked to investigate the effect of light intensity on the rate of photosynthesis using pondweed.

(a)

Describe a method the student could use.

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(b)

The student was told to place a glass tank of water between the lamp and the test tube.

Explain why.

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Question 0

6 marks

A grower measured the rate of photosynthesis of pepper plants in a greenhouse at different temperatures. The light intensity and carbon dioxide concentration were kept constant.

The results are shown in the table.

Temperature in °C	Rate of photosynthesis in arbitrary units
10	8
20	16
30	25
35	28
40	20
45	7

(a)

Explain why the rate of photosynthesis increased between 10 °C and 35 °C.

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(b)

Explain why the rate of photosynthesis decreased between 40 °C and 45 °C.

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(c)

Calculate the percentage decrease in the rate of photosynthesis between 35 °C and 45 °C.

Percentage decrease = __________ %

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Question 0

3 marks

Some plants have variegated leaves. Part of a variegated leaf is green and part of it is white.

(a)

The rate of photosynthesis of a variegated leaf is lower than the rate of photosynthesis of an all-green leaf of the same size.

Explain why.

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(b)

Suggest one reason why the leaves of an all-green plant growing in a garden might contain less chlorophyll than normal.

/ 1

Question 0

5 marks

Students investigated the effect of carbon dioxide concentration on the rate of photosynthesis. They placed pondweed in test tubes containing different concentrations of sodium hydrogencarbonate solution, which releases carbon dioxide into the water. They counted the number of bubbles of gas produced in one minute.

The results are shown in the table.

Concentration of sodium hydrogencarbonate in %	Test 1	Test 2	Test 3	Mean
0.0	2	3	1	2.0
0.2	11	9	10	10.0
0.4	19	21	20	20.0
0.6	27	26	28	27.0
0.8	28	27	41	X

(a)

One result in the 0.8 % row is anomalous.

Calculate the mean value X, ignoring the anomalous result.

X = __________ bubbles per minute

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(b)

Explain why the mean rate of photosynthesis did not increase much between 0.6 % and 0.8 % sodium hydrogencarbonate.

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(c)

Give one variable the students should have controlled in this investigation.

/ 1

Question 0

4 marks

A student investigated the effect of light intensity on the rate of photosynthesis. She placed pondweed in a test tube of water and counted the bubbles produced in one minute with a lamp at 10 cm, 20 cm and 30 cm from the test tube.

The student carried out the investigation on a laboratory bench with the laboratory lights switched on. She took one reading at each distance.

(a)

Explain why having the laboratory lights switched on reduces the validity of the student's results.

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(b)

Explain why the student should have taken repeat readings at each distance.

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Question 0

5 marks

A student used a lamp to shine light onto pondweed. The light intensity reaching the pondweed is inversely proportional to the square of the distance from the lamp.

$\text{light intensity} \propto \dfrac{1}{d^2}$

where $d$ is the distance from the lamp in cm.

(a)

Calculate the light intensity, in arbitrary units, when the lamp is 25 cm from the pondweed and when it is 50 cm from the pondweed.

At 25 cm: __________ arbitrary units

At 50 cm: __________ arbitrary units

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(b)

With the lamp at 25 cm the rate of photosynthesis was 36 bubbles per minute. At this distance light intensity was the limiting factor.

Predict the rate of photosynthesis with the lamp at 50 cm from the pondweed.

Use ideas about light intensity in your answer.

Rate = __________ bubbles per minute

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(c)

The student then moved the lamp to 5 cm from the pondweed. The rate of photosynthesis was much lower than predicted from the light intensity.

Suggest one reason why.

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Question 0

5 marks

The graph shows the rate of photosynthesis of a tomato plant at different light intensities under three different sets of conditions.

Curve A: 0.04 % carbon dioxide, 20 °C
Curve B: 0.40 % carbon dioxide, 20 °C
Curve C: 0.40 % carbon dioxide, 30 °C

(a)

At low light intensity, all three curves are the same.

Explain what this shows.

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(b)

Explain why curve C levels off at a higher rate of photosynthesis than curve B.

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(c)

Name the factor that is limiting the rate of photosynthesis at point X on curve A.

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Question 0

6 marks

A grower produces tomatoes in a greenhouse. She sells the tomatoes for £2.00 per kg.

She tested three ways of increasing the rate of photosynthesis in her greenhouse. The table shows her results for one year.

Conditions in the greenhouse	Extra cost per year in £	Yield of tomatoes in kg per year
No enhancement	0	3000
Extra lighting added	1800	3600
Carbon dioxide enrichment added	900	3900
Extra heating added	2400	3750

(a)

Calculate the extra profit the grower would make in one year by adding carbon dioxide enrichment.

Extra profit = £ __________

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(b)

The grower can only afford to use one of the three methods.

Use the data in the table to explain which method she should choose.

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Cell Biology

Organisation

Infection & Response

Bioenergetics

Homeostasis & Response

Inheritance, Variation & Evolution

Ecology

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