National 5
Photosynthesis Homework
1. Describe the two stages of photosynthesis including the names of the raw
materials and products for each stage. (5)
2.The graph below shows the effects of two different environmental factors on the
rate of photosynthesis.
(a) What are the limiting factors at points X and Y?
X
1
Y
1
(b) Suggest one way that the rate of photosynthesis can be measured.
1
(c) During the first stage of photosynthesis, light energy is used.
(i) Where is light energy trapped in the cell?
1
(ii) State one use of this light energy.
1
(d) (i) Name the second stage of photosynthesis.
1
(ii) Name the carbohydrate produced during the second stage of
photosynthesis.
1
3. Answer the following past paper question:
4. The diagram below summarises the stages of photosynthesis.
Gas B
H
Phase 1
Water
ADP + P
Phase 2
ATP
Gas A
Glucose
a) (i) Name the two gases shown.
Gas A
(ii)
_____________________
Gas B ____________________
1
Which of the phases numbered is known as photolysis?
__________________________________
(iii)
1
Highlight the arrow which shows the conversion of light energy to chemical energy.
1
(iv) Name the substance which captures the energy of the sunlight
______________________________________________________
1
b) The final product of photosynthesis is glucose.
It may be converted to a carbohydrate used in the construction of cell walls.
Name this sugar.
________________________________
1
c) Identify two ways in which a tomato grower might control factors which limit the rate of
photosynthesis so that they could produce early crops or bigger yields.
1
_______________________________________________
2
________________________________________________
2
5. An experiment was carried out to find the rate of photosynthesis of a group of plants at
different concentrations of carbon dioxide.
This was repeated at 2 different light intensities. The results are given in the table below:
CO2 concentration / %
of air
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
Rate of photosynthesis / arbitrary units
Low light intensity
High light intensity
0
0
20
20
29
35
35
47
39
68
42
84
45
89
46
90
46
90
46
90
1. Plot the results on a graph with two labelled lines
(X-axis - CO2 concentration; Y-axis - Rate of photosynthesis)
2. Describe the patterns shown by the two graphs. Refer to numbers on the graph for this
answer.
3. Label your graph to show the region where carbon dioxide is the limiting factor.
4. Explain how you identified this.
5. Label your graph to show where light intensity becomes the limiting factor.
6. Explain how you identified this.
7. What other factors may limit the rate of photosynthesis?
8. In agriculture, farmers may sometimes add carbon dioxide to the air inside their
greenhouses.
a. What is the advantage of doing this?
b. How else can market gardeners use information about limiting factors to produce
vegetable such as lettuces throughout the year?