The graph below shows the variation in the concentration of atmospheric carbon dioxide since
1970.
375
370
365
360
355
CO 2
concentration
/ ppm
350
345
340
335
330
325
2000
1995
1990
1985
1980
1975
320
1970
1.
[Source: C D Keeling and T P Whorf, Atmosphere CO2 concentrations (ppm) derived from in situ air samples,
collected at Mauna Loa Observatory, Hawaii]
The annual fluctuation is mainly the result of changes in the levels of photosynthesis associated
with the seasons in Northern Hemisphere forests.
(a)
(i)
Describe the overall trend shown in the graph.
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(1)
(ii)
Suggest a cause for the overall trend throughout the period 1970–1999.
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(1)
1
(b)
(i)
Using a clear label, identify any one point on the graph which shows the CO2 level
in mid-summer.
(1)
(ii)
Explain why the concentration of CO2 varies with the seasons.
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(2)
(c)
Identify one gas, other than CO2 , which is contributing to the enhanced greenhouse
effect.
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(1)
(Total 6 marks)
2.
The diagram below shows possible pathways for the breakdown of glucose in various cells.
Glucose
A
Process Q
(no oxygen present)
B
(a)
C+D
Process R
(oxygen present)
D+E
State the names of processes Q and R.
Q:
...........................................................................................................................
(1)
R:
...........................................................................................................................
(1)
2
(b)
Deduce the names of substances A and D.
A:
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(1)
D:
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(1)
(c)
State the organelle in which process R takes place.
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(1)
(Total 5 marks)
3.
(a)
State the main photosynthetic pigment in plants.
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(1)
(b)
State the two materials used to convert carbon dioxide to organic molecules in plants.
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(2)
3
(c)
Explain two ways in which the rate of photosynthesis can be measured.
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(4)
(Total 7 marks)
4.
(a)
Explain the properties of water that allow living organisms to use it as a habitat.
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(3)
(b)
List two end products of aerobic cell respiration.
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(2)
4
(c)
State the name of the molecule that is the source of the oxygen released by plants during
photosynthesis.
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(1)
(Total 6 marks)
5.
(a)
Draw and label the structure of a chloroplast as seen in electron micrographs.
(3)
(b)
Explain the relationship between the absorption spectrum and the action spectrum of
photosynthetic pigments.
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(3)
(Total 6 marks)
6.
Up to two additional marks are available for the construction of your answers.
(2)
(a)
Draw a labelled diagram showing stages of the carbon cycle.
(5)
(b)
Explain how the rate of photosynthesis can be measured.
(7)
(c)
Describe why carbohydrates and lipids are used as energy stores.
(6)
(Total 20 marks)
5
7.
During photosynthesis in plants, light energy is absorbed by chlorophyll. This energy is then
used to carry out photolysis, which supply substances that are needed to convert carbon dioxide
into organic molecules such as glucose.
(a)
State the names of two products of photolysis in photosynthesis.
1. .................................................................................................................................
2. .................................................................................................................................
(2)
(b)
Explain briefly one method for measuring the rate of photosynthesis in a plant.
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(2)
(c)
The rate of photosynthesis is affected by light intensity. Draw a line on the graph below
to show the relationship between light intensity and the rate of photosynthesis.
rate of photosynthesis
light intensity
(2)
6
(d)
State two factors in the environment of a plant, apart from light intensity, that can affect
the rate of photosynthesis in the plant.
1. .................................................................................................................................
2. .................................................................................................................................
(2)
(Total 8 marks)
8.
Explain the effect of substrate concentration on enzyme activity.
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(Total 3 marks)
7
9.
The diagrams below show various molecular structures.
I.
O
CH3
(CH 2) n
II.
O
HOH 2 C
H
C
C
C
OH
III.
H
C
H
OH
O
H
H
C
C
OH
OH
IV.
CH 2 OH
C
H H
OH
R
H
H
C
O
N
C
C
H
H
OH
(a)
C
C
H
OH
OH
OH
Identify which of the diagrams represent
(i)
the structure of glucose;
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(1)
(ii)
the structure of amino acids;
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(1)
(iii)
the structure of fatty acids.
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(1)
8
(b)
Discuss which of the molecules are most similar in structure.
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(3)
(Total 6 marks)
10.
Draw the structure of a fatty acid.
(Total 1 mark)
9