IB Questionbank Biology 1
2.9 Photosynthesis Paper 2 Possible Questions Extended Response
1. (a) State the location in the chloroplast of the following reactions of photosynthesis.
Light-independent reactions: .......................................................................................
Light-dependent reactions: .......................................................................................... (2)
(b) Explain what happens to the electrons in the light-dependent reactions of photosynthesis.
......................................................................................................................................
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(Total 5 marks)
2. (a) Explain why carbon dioxide concentration is a limiting factor of photosynthesis.
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(b) Explain the relationship between the structure of the chloroplast and its function.
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IB Questionbank Biology 2
(3)
(c) State two products of the light-dependent reactions.
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..................................................................................................................................... (2)
(Total 8 marks)
3. Up to two additional marks are available for the construction of your answers. (2)
(a) Living organisms at every trophic level are part of the carbon cycle. Draw a labelled
diagram of the carbon cycle to show the processes involved. (9)
(b) Explain, using an example of a food chain, how trophic levels can be deduced. (4)
(c) Explain methods that can be used to measure the rate of photosynthesis. (5)
(Total 20 marks)
4. Up to two additional marks are available for the construction of your answers. (2)
(a) All organisms in an ecosystem are involved in the carbon cycle. Outline the roles of
living organisms in the carbon cycle. (8)
(b) Explain how triose phosphate is produced and used in the chloroplasts of a plant. (5)
(c) Explain the conditions that are needed to allow a seed to germinate. (5)
(Total 20 marks)
IB Questionbank Biology 3
5. (a) Draw a labelled diagram of the structure of a chloroplast as seen with an electron
microscope. (4)
(b) Describe how water is carried by the transpiration stream. (7)
(c) Explain how flowering is controlled in long-day and short-day plants. (7)
(Total 18 marks)
6. The graph below shows the results of an experiment to determine the effect of salt (NaCl)
concentration on photosynthesis of the freshwater green alga Chlorella vulgaris. The
experiment attempted to determine the effect of salt concentration on the light-dependent
reactions overall and separately on photosystem I and photosystem II.
[Source: M M El-Sheekh, “Inhibition of the water splitting system by sodium chloride stress in the green alga
Chlorella vulgaris”, Brazilian Journal of Plant Physiology, Volume 16, Issue 1, Figure 1, (2004)]
(a) Describe the effect of salt concentration on the activity of the light-dependent reactions
overall.
......................................................................................................................................
...................................................................................................................................... (1)
(b) Compare the effect of increasing salt concentration on photosystem I with the effect on
photosystem II.
......................................................................................................................................
...................................................................................................................................... (1)
IB Questionbank Biology 4
(c) When salt concentration is increased, some algal cells increase their rates of cyclic
photophosphorylation. Deduce the reasons for this.
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(d) Using the graph, predict the effect of high salt concentration on the growth of Chlorella
vulgaris. Give a reason for your answer.
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(Total 6 marks)
IB Questionbank Biology 5
7. Primary production is directly related to the amount of photosynthesis that occurs in a cubic
metre of water. In the waters around Bermuda (32° N) in the Atlantic Ocean, microscopic
phytoplankton are the producers. They use trace nutrients from seawater in their metabolism.
These nutrients are a limiting factor in total population size. A dense phytoplankton population
makes the water cloudy. The data shows primary production per day for each month for the year
2000 at different water depths.
[Source: DataStreme Ocean, American Meteorological Society (2004). Reprinted with permission.]
(a) State the month when total photosynthesis was greatest.
...................................................................................................................................... (1)
(b) Identify, with a reason, the water depth that receives no light.
......................................................................................................................................
...................................................................................................................................... (1)
IB Questionbank Biology 6
(c) In the upper 40 m there is a drop in photosynthesis from March to June. This is probably
due to lack of nutrients, reducing the population density.
Suggest, with a reason other than nutrient levels, what might have increased
photosynthesis at 100 m from April to August.
......................................................................................................................................
...................................................................................................................................... (1)
(d) Compare production in March with production in September.
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...................................................................................................................................... (3)
(Total 6 marks)
IB Questionbank Biology 7
8. Global atmospheric carbon dioxide levels are rising. A study was carried out to test if the
temperature dependence of photosynthesis was altered by elevated atmospheric CO2.
Maize plants were grown in natural sunlight in controlled environmental chambers at different
temperatures using current atmospheric and doubled CO2 levels.
The graph below shows daily patterns of CO2 exchange at three different temperatures.
Open shapes (○, Δ, □) represent current atmospheric CO2 levels and closed shapes (●, ▲, ■)
represent elevated CO2 levels.
[Reprinted from: Kim, S H et al. 2007. “Temperature dependence of growth, development, and photosynthesis in maize under elevated CO2”. Environmental and Experimental Botany. Vol 61. Pp 224–236.]
(a) (i) State the time at which carbon dioxide exchange rate is maximal.
........................................................................................................................... (1)
(ii) Explain the reasons for maximum carbon dioxide exchange rate at this time.
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IB Questionbank Biology 8
(b) State the temperature that resulted in the highest rate of photosynthesis under current
atmospheric conditions.
...................................................................................................................................... (1)
(c) Using the data in the graph, discuss whether rising carbon dioxide levels in the
atmosphere will increase growth rates in maize.
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(Total 6 marks)
9. Up to two additional marks are available for the construction of your answers. (2)
(a) Draw a labelled diagram showing the tissues present in a dicotyledonous leaf. (4)
(b) Outline the light-dependent reactions of photosynthesis. (6)
(c) Explain the effect of light intensity and temperature on the rate of photosynthesis. (8)
(Total 20 marks)
IB Questionbank Biology 9
10. The rate of photosynthesis in the marine seagrass, Zostera marina, was investigated under a
range of pH conditions. After a period of darkness, the plants were illuminated at a constant
light intensity at 15°C and the rate of photosynthesis was measured. Zostera marina can use
both dissolved carbon dioxide (CO2) and hydrogen carbonate ions for photosynthesis. The rate
of photosynthesis is plotted on the y-axis on the left. In addition, the concentration of carbon
dioxide was measured for each pH investigated and is plotted on the y-axis on the right.
[Source: Plant physiology by AMERICAN SOCIETY OF PLANT PHYSIOLOGISTS. Copyright 2008 Reproduced
with permission of AMERICAN SOCIETY OF PLANT BIOLOGISTS in the format CD ROM via Copyright
Clearance Center.]
(a) State the carbon dioxide concentration at pH 7.2.
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...................................................................................................................................... (1)
IB Questionbank Biology 10
(b) Calculate the percentage decrease in the rate of photosynthesis from pH 7 to pH 7.5.
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(c) Outline the relationship between pH and the rate of photosynthesis.
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(d) Suggest how Zostera marina can perform photosynthesis even at very low carbon dioxide
concentrations.
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(e) Based on the information and data provided, discuss the role of one limiting factor, other
than carbon dioxide, and suggest how this would affect the rate of photosynthesis.
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(Total 7 marks)
IB Questionbank Biology 11
11. The effect of temperature on photosynthesis was studied in sweet orange (Citrus sinensis) using
leaf discs. The production of oxygen was used to measure the rate of photosynthesis.
Gross photosynthesis refers to the sum of net photosynthesis and respiration. Net photosynthesis
was calculated by subtracting the rate of respiration in the dark from gross photosynthesis.
[Source: Adapted from R Ribeiro et al. 2006. Ciência e Agrotecnologia. Vol 30. Pp 670–678.]
(a) Identify the optimum temperature for photosynthesis in this plant.
...................................................................................................................................... (1)
(b) Determine the difference between gross photosynthesis and net photosynthesis at 40°C
and 50°C.
40°C: ..........................................................................................................................
50°C: .......................................................................................................................... (2)
(c) Deduce what happens to the rate of respiration as the temperature increases between 40°C
and 50°C.
...................................................................................................................................... (1)
IB Questionbank Biology 12
(d) (i) Describe the general pattern of change in photosynthesis in sweet orange as the
temperature increases.
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...........................................................................................................................
........................................................................................................................... (1)
(ii) Compare the effect of temperature on photosynthesis with the effect of temperature
on respiration in sweet orange.
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(Total 7 marks)
12. Explain the reasons for
(a) a large area of thylakoid membrane in the chloroplast.
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(b) low rates of photosynthesis in plants growing beneath trees, where the light has already
passed through the trees’ leaves.
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IB Questionbank Biology 13
(2)
(c) large amounts of RuBP carboxylase in the chloroplast;
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(Total 6 marks)
IB Questionbank Biology 14
13. The graph below shows the variation in the concentration of atmospheric carbon dioxide since
1970.
375
370
365
360
355
350
345
340
335
330
325
320
19
70
19
75
19
80
19
85
19
90
19
95
20
00
COconcentration
/ ppm
2
[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.
...........................................................................................................................
........................................................................................................................... (1)
(ii) Suggest a cause for the overall trend throughout the period 1970–1999.
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IB Questionbank Biology 15
(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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(c) Identify one gas, other than CO2 , which is contributing to the enhanced greenhouse
effect.
..................................................................................................................................... (1)
(Total 6 marks)
14. The unicellular green alga Phaeodactylum tricornutum is photosynthetic. Cell biologists
genetically modified this organism by adding a glucose transporter gene. The modified and
unmodified algae were grown in a nutrient medium under a series of different conditions and
the growth rate of the cells was measured.
12
10
8
6
4
2
0
0 2 4 6 8 0 2 4 6 8
Time / days
Cell density /10 cells cm
Key:
= light and no glucose in the medium
= light and glucose in the medium
= dark and glucose in the medium
Unmodified algae Modified algae
–37
[Source: L A Zaslavskaia, et al., Adapted (2001) Science, 292, pages 2073–2075]
(a) State the role of glucose in the metabolism of cells.
..................................................................................................................................... (1)
IB Questionbank Biology 16
(b) Deduce where you would expect to find the glucose transporter protein in the modified
algae cells.
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(c) Compare the effect of light on the modified and the unmodified cells.
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Commercially, unmodified algae are grown in shallow sunlit ponds or illuminated containers.
The cells only grow in the top few centimetres. However, the modified algae can grow at any
depth.
(d) Explain why the modified algae can grow at any depth whereas the unmodified algae can
only grow at the surface.
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(Total 8 marks)
IB Questionbank Biology 17
15. Copepods are very small crustaceans and an important component of plankton in the Arctic sea
ice. The distribution of copepods, which feed on microalgae, can be related to the food and
predators. The biomass of microalgae was measured and the concentration of chlorophyll a was
calculated. The graphs below show how the concentration of chlorophyll a and copepods
change with depth.
Dep
th /
m
Microalgae
Chlorophyll a / mg m–3
Dep
th /
m
Copepods
Relative numbers
[Source: Martin Fortier, et. al., Visual predators and the diel vertical migration of copepods under Arctic sea ice during the midnight
sun” (2001), vol. 23, issue 11, pp. 1263–1278, by permission of Oxford University Press]
(a) State the amount at a depth of 30 m below sea level of
(i) chlorophyll a;
..........................................................................................................................
(ii) copepods.
.......................................................................................................................... (2)
IB Questionbank Biology 18
(b) Describe the distribution of microalgae.
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(c) Discuss factors that could affect the distribution of copepods.
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(Total 7 marks)
IB Questionbank Biology 19
16. The cyanobacterium (Calothrix elenkenii) is cultivated as a source of photosynthetic pigments
for use in research and industry. The chart below shows the quantity of two of the pigments
produced when exposed to a day of continuous dark, a day of 16 hours light and 8 hours dark
and a day of continuous light. This was repeated in both aerobic and anaerobic conditions.
Key:
Dark
Dark
Light – Dark
Light – Dark
Light
Light
Aerobic
Anaerobic
6.05.55.04.54.03.53.02.52.01.51.00.50.0
Amount of Pigment / g cm–3μ
Chlorophyll
β-Carotene
[Source: Reprinted from Journal of Plant Physiology, Vol 161, Parsanna et al., “Modulation of pigment…” pages 1125–1132,
copyright (2002), with permission from Elsevier.]
(a) Identify the light conditions that cause most chlorophyll to be made when the
cyanobacterium is cultivated anaerobically.
.................................................................................................................................... (1)
(b) Calculate the percentage increase in chlorophyll grown anaerobically in the light,
compared with anaerobically in the dark.
.................................................................................................................................... (1)
(c) Compare pigment production in different aerobic conditions.
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IB Questionbank Biology 20
(d) Discuss why having more than one photosynthetic pigment is an advantage to
cyanobacterium.
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(Total 7 marks)
17. Studies were carried out on the leaves of the wild type of the flowering mustard plant
(Arabidopsis thaliana) to determine the pigment composition of the thylakoid membrane. The
results were compared with the leaves of a mutant strain of the plant. These studies were
repeated using thylakoid membranes from leaves grown in cultures deficient in either iron or
magnesium.
Strain of Plant Mineral Deficiency Chlorophyll /
g g–1
leaf
Carotenoids /
g g–1
leaf
None 454 16
Wild Type Iron 441 71
Magnesium 317 64
None 387 67
Mutant Iron 317 81
Magnesium 172 95
[Source: Lu et al, (1995), Botanical Bulletin of Academia Sinica, 36, pages 175–179]
(a) State the concentration of chlorophyll found in the leaves of the mutant strain of plant
when deficient in iron.
.................................................................................................................................... (1)
(b) (i) Calculate the percentage increase in carotenoids found in the wild type when
magnesium is deficient.
.......................................................................................................................... (1)
IB Questionbank Biology 21
(ii) Suggest why magnesium deficiency causes the changes shown in the pigment
content of the leaves.
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(c) Using the data in the table, outline the effects of iron deficiency on the pigment content of
the leaves.
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(Total 6 marks)
IB Questionbank Biology 22
18. Plants that grow in the desert have many adaptations that enable them to cope with full sunlight
and low water availability, such as thicker leaves with reduced surface area. Researchers have
also observed that leaf pubescence (presence of white leaf surface hairs) may be another
adaptation to dry environments. A study was done to evaluate the effects of leaf pubescence on
two species of Californian plants, Encelia farinosa, a desert species with pubescent leaves and
Encelia californica, a native of the moist coast with non-pubescent leaves.
The graph below shows the absorption spectrum of intact leaves of both species in the
photosynthetically active spectrum between the wavelengths 400 nm (blue light) and 800 nm
(red light) of light.
Absorption
/ %
100
90
80
70
60
50
40
20
10
0
400 450 500 550 600 650 700 750 800
Blue Green Yellow Orange Red
Wavelength / nm
Key:
E. californica
E. farinosa
30
[Source: From J. Ehleringer et al., “Leaf Pubescence: Effects on Absorptance and Photosynthesis in a Desert Shrub”, Science (23
April 1976), vol. 192, issue 4237, pp. 376-377. Reprinted with permission from AAAS]
(a) Calculate the difference in absorption between E. farinosa and E. californica at 600 nm.
....................................................................................................................................
.................................................................................................................................... (1)
(b) Suggest a possible explanation for the decrease in absorption at 550 nm for E. californica.
....................................................................................................................................
.................................................................................................................................... (1)
(Total 2 marks)
IB Questionbank Biology 23
19. The following graph shows the rate of CO2 uptake of three leaves of Encelia farinosa with
different absorbance coefficients (x) (proportion of light absorbed) which is related to the degree
of pubescence of the leaf. The higher the coefficient the more light is absorbed.
Rate of CO2 uptake /
n mol CO2 cm–2 sec–1
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
x = 0.82
x = 0.65
x = 0.53
0 50 100 150 200 250
Light intensity / mmol cm–2 sec–1
[Source: From J. Ehleringer et al., “Leaf Pubescence: Effects on Absorptance and Photosynthesis in a Desert Shrub”, Science (23
April 1976), vol. 192, issue 4237, pp. 376-377. Reprinted with permission from AAAS]
(a) Using the graph above, compare the maximum CO2 uptake of E. farinosa at absorbance
coefficients 0.82 and 0.53.
....................................................................................................................................
.................................................................................................................................... (1)
(b) (i) Using the data, deduce the relationship between pubescence and light absorption.
..........................................................................................................................
.......................................................................................................................... (1)
IB Questionbank Biology 24
(ii) Evaluate the relationship of leaf pubescence and CO2 uptake.
..........................................................................................................................
.......................................................................................................................... (1)
(c) Suggest how natural selection may have caused the difference in leaf pubescence between
E. farinosa and E. californica.
....................................................................................................................................
.................................................................................................................................... (1)
20. Further research was carried out to evaluate the relationship between leaf pubescence during the
growing season of E. farinosa and its water use efficiency. Water use efficiency is defined as
the amount of CO2 uptake divided by the amount of water lost by transpiration from the leaf.
The graph below shows the seasonal change in leaf pubescence and water use efficiency of E.
farinosa. The period of maximum growth is indicated on the graph. During the course of the
year the optimum temperature for photosynthesis remains at 30C while the air temperature
fluctuates from a high of 38C in the summer months (May–September) to a low of 8C during
the winter months (December–February).
Wat
er u
se e
ffci
ency
/ a
rbit
rary
unit
s
6
5
4
2
1
0 M J J A S O N D J F M A M
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
Pu
bescen
ce Thick
ness /m
m
Key:
Water use effciency
Pubescence thickness
Time of the year / month maximum growth period
new leaves emerge
3
[Source: Ecology by William K. Smith and Park S. Nobel. Copyright 1977 by Ecological Society of America. Reproduced with
permission of Ecological Society of America in the format of CD-Rom via Copyright Clearance Center.]
IB Questionbank Biology 25
(a) State the month with the highest water use efficiency.
.................................................................................................................................... (1)
(b) Outline the changes in leaf pubescence of E. farinosa during the year.
....................................................................................................................................
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....................................................................................................................................
.................................................................................................................................... (2)
(c) Analyse the change in the level of water use efficiency between July and December for E.
farinosa.
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(Total 11 marks)
IB Questionbank Biology 26
21. There are many abiotic factors that affect the rate of photosynthesis in terrestrial plants. Wheat
is an important cereal crop in many parts of the world. Wheat seedlings were grown at three
different concentrations of carbon dioxide (in parts per million) and the rate of photosynthesis
was measured at various light intensities.
50
40
30
20
10
00 5 10 15 20
Light intensity / × 10 lumen m
2
3
2
2
2
–2
–1
Rat
e o
f p
hoto
syn
thes
is /
l
CO
m
in
key:
1300 ppm CO
500 ppm CO
280 ppm CO
[Source: Adapted from J P Kimmins, 1997 Forest Ecology, (2nd edition) page 161]
(a) Describe the relationship between the rate of photosynthesis and light intensity for wheat
seedlings grown at a CO2 concentration of 500 ppm.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
..................................................................................................................................... (2)
IB Questionbank Biology 27
(b) Outline the effect of CO2 concentration on the rate of photosynthesis of the wheat
seedlings.
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(c) The normal atmospheric concentration of CO2 is 370 ppm. Deduce the effect of doubling
the CO2 concentration to 740 ppm on the growth of wheat plants.
.....................................................................................................................................
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.....................................................................................................................................
..................................................................................................................................... (2)
22. Leaf area and chlorophyll levels were measured in sun leaves and shade leaves of Hedera helix
(English Ivy) and Prunus laurocerasus (Cherry Laurel). Sun leaves developed under maximal
sunlight conditions while shade leaves developed at reduced sunlight levels in the shadow of
other leaves.
Species Leaf Type Chlorophyll/
g ml-1
Leaf Area/
cm2
Ivy Shade 4.3 72.6
Sun 3.8 62.9
Laurel Shade 4.7 38.7
Sun 4.2 25.7
[Source: D Curtis, Plant Ecology independent project, 1990]
IB Questionbank Biology 28
(a) Calculate the percentage increase in the amount of chlorophyll in shade leaves of ivy
compared to sun leaves of ivy
.....................................................................................................................................
.....................................................................................................................................
..................................................................................................................................... (1)
(b) Suggest a reason for the differences in chlorophyll concentration and leaf area in sun and
shade leaves in these two species.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
..................................................................................................................................... (2)
(Total 10 marks)
23. Up to two additional marks are available for the construction of your answers. (2)
(a) Draw a labelled diagram showing the structure of a plasma membrane. (4)
(b) Outline the role of chlorophyll and the effects of temperature, light intensity and carbon
dioxide concentration on the rate of photosynthesis. (6)
(c) Explain the production of energy during aerobic respiration from pyruvate that has been
produced by glycolysis. (8)
(Total 20 marks)
24. Explain how the light-independent reactions of photosynthesis rely on light-dependent
reactions. (Total 8 marks)
IB Questionbank Biology 29
25. Up to two additional marks are available for the construction of your answers. (2)
(a) Draw and label the action spectrum of photosynthesis. (4)
(b) Explain the relationship between the structure of the chloroplast and the light-dependent
reactions of photosynthesis. (8)
(c) Outline the potential harmful effects of increased carbon dioxide concentration on the
ecosystem and state one measure that could be taken to reduce the amount of carbon
dioxide in the atmosphere. (6)
(Total 20 marks)
26. Explain the reactions involving the use of light energy that occur in the thylakoids of the
chloroplast. (Total 8 marks)
27. Outline the effect of temperature, light intensity and carbon dioxide concentration on the rate of
photosynthesis. (Total 6 marks)
28. State two products of the light dependent reaction of photosynthesis.
............................................................................................................................................... (Total 2 marks)
IB Questionbank Biology 30
29. (a) Photosynthesis consists of two groups of reactions. State the names of the two groups of
reactions.
.....................................................................................................................................
..................................................................................................................................... (1)
(b) Draw and label the action spectrum of photosynthesis.
(3)
(c) Explain the concept of limiting factors with reference to light intensity.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
..................................................................................................................................... (2)
(Total 6 marks)
IB Questionbank Biology 31
30. (a) Photosynthesis consists of two sets of reactions. State the names of these two sets.
......................................................................................................................................
...................................................................................................................................... (1)
(b) Outline how one specific limiting factor affects the rate of photosynthesis.
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
...................................................................................................................................... (2)
(c) Explain the production of ATP by chemiosmosis during photosynthesis.
......................................................................................................................................
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...................................................................................................................................... (3)
(Total 6 marks)
IB Questionbank Biology 32
31. (a) State where in the chloroplast the enzymes of the Calvin cycle are located.
..................................................................................................................................... (1)
(b) Outline the fate of ribulose biphosphate (RuBP) during photosynthesis
.....................................................................................................................................
.....................................................................................................................................
..................................................................................................................................... (2)
(c) A green plant is not photosynthesizing at its maximum rate when the light intensity is
increased.
Suggest why there is no increase in the rate of photosynthesis
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
..................................................................................................................................... (2)
(Total 5 marks)
IB Questionbank Biology 33
32. The graph below shows the effect of light intensity on photosynthesis at 0.1% carbon dioxide
concentration.
Rate of photosynthesis /arbitrary units
Light intensity / arbitrary units
(a) On the graph above, draw the results obtained at 0.01% carbon dioxide. (1)
(b) Outline the fate of the oxygen and hydrogen which are produced in the photolysis of
water during photosynthesis.
Oxygen: ...............................................................................................................
...............................................................................................................
Hydrogen ...............................................................................................................
............................................................................................................... (2)
(c) The energy produced in photosynthesis can enter a food chain. Explain how this energy
can be lost before it reaches the last link in the chain.
....................................................................................................................................
....................................................................................................................................
.................................................................................................................................... (2)
(Total 5 marks)
IB Questionbank Biology 34
33. (a) State the main photosynthetic pigment in plants.
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(b) State the two materials used to convert carbon dioxide to organic molecules in plants.
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(c) Explain two ways in which the rate of photosynthesis can be measured.
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(Total 7 marks)
34. 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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IB Questionbank Biology 35
(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)
(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)
IB Questionbank Biology 36
35. (a) State the site of the light-independent reactions in photosynthesis.
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The absorption spectrum of chlorophyll a and chlorophyll b are shown in the graph below.
Absorbance
400 500 600 700
Wavelength / nm
chlorophyll b
chlorophyll a
(b) On the graph above, draw the action spectrum of photosynthesis for a green plant. (1)
(c) Explain photophosphorylation in terms of chemiosmosis.
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(Total 5 marks)
IB Questionbank Biology 37
36. (a) State where, in the chloroplast, the enzymes of the Calvin cycle are located.
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(b) Explain how the proton gradient in the chloroplast is generated by chemiosmosis.
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(c) Explain the relationship between the position of a leaf on a tree and the photosynthetic
rate of the leaf.
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(Total 6 marks)
IB Questionbank Biology 38
37. (a) Explain how photosynthesis can be measured both directly and indirectly.
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(b) Outline two uses of absorbed carbohydrates in humans.
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(c) The diagram below represents an energy pyramid and four trophic levels.
IV
III
II
I100 000 kJ m yr–2 –1
[Source: adapted from www.bio.miami.edu/dana/160/pyramid.gif]
(i) Identify the trophic level of the organisms indicated below.
I. ...............................................................................................................
IV. ............................................................................................................... (2)
(ii) Calculate the approximate amount of energy in kilojoules transferred in m–2
yr–1
from trophic level I to trophic level II.
..................................................................................................................... kJ (1)
(Total 8 marks)
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