New Senior Secondary Mastering Biology (Second Edition)
Question Bank
 Chapter 21
Chapter 21
Multiple-choice questions
Photosynthesis
Multiple-choice questions
[10143393]
* The graph below shows the effect of carbon dioxide concentration on the rate of
photosynthesis of a plant at two different light intensities.
4 arbitrary units
of light intensity
rate of
photosynthesis
Q
1 arbitrary unit
of light intensity
P
carbon dioxide concentration
Which of the following are probably the limiting factors of the rate of
photosynthesis at points P and Q?
A
B
C
D
P
light intensity
light intensity
carbon dioxide concentration
carbon dioxide concentration
Q
light intensity
carbon dioxide concentration
light intensity
carbon dioxide concentration
C
---------------------------------------------------
© Oxford University Press
21-1
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143403]
**Two variegated leaves were exposed to light and radioactive carbon dioxide
(14CO2) was supplied to them for different periods of time. Photographic films
were then used to detect the radioactivity in different areas of the two leaves.
appearance of leaves
green area
photographic films
exposed to light
14
and CO2 supplied
for 14 minutes
yellow area
outline of
leaf
dark areas
exposed to light and
14
CO2 supplied for
18 hours
Which of the following is the best explanation for the results?
A
14
B
C
D
14
CO2 diffuses into the green areas of the leaves faster than into the yellow
areas.
CO2 can be assimilated in the areas of the leaf that lack chlorophyll.
Photosynthetic products eventually spread throughout the leaf.
Photosynthesis can take place slowly in the yellow areas.
C
--------------------------------------------------[10143432]
* Which of the following steps is the essential link between photochemical
reactions and the Calvin cycle of photosynthesis?
A
B
C
D
splitting of water molecules
carbon dioxide fixation
raising the energy levels of chlorophyll molecules
production of reduced hydrogen carriers
D
--------------------------------------------------© Oxford University Press
21-2
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143446]
**Air containing two kinds of oxygen, 16O2 and 18O2, was bubbled through an
algal suspension. The air supply was then stopped and the concentrations of the
two kinds of oxygen in the suspension were monitored in the following 55
minutes. During this period, the algal suspension was kept alternately in the dark
and under light. The results are shown in the graph below.
dark
light
dark
concentrations of
oxygen in the
algal suspension
16
O2
18
O2
0
10
20
30
time (minute)
40
50
Which of the following is a correct deduction from the results of the experiment?
A
B
C
D
16
O2 is involved in photosynthesis but not in respiration.
O2 is involved in respiration but not in photosynthesis.
The alga is able to distinguish between the two kinds of oxygen.
The rate of diffusion of 18O2 is lower than that of 16O2.
18
C
--------------------------------------------------[10143459]
* Photochemical reactions of photosynthesis can be made to occur experimentally
in the absence of
A
B
C
D
water.
carbon dioxide.
chlorophyll.
ADP.
B
--------------------------------------------------© Oxford University Press
21-3
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143460]
 The diagram below shows the Calvin cycle of photosynthesis.
carbon dioxide
5-C compound
X
Z
3-C compound
triose phosphate
Y
Which of the following processes require energy from ATP?
A
B
C
D
X and Y only
X and Z only
Y and Z only
X, Y and Z
C
--------------------------------------------------[10143476]
* The table below shows the rate of photosynthesis of a water plant under five
different conditions.
Condition
P
Q
R
S
T
Light intensity (arbitrary unit)
6
6
6
6
7
0.03
0.03
0.13
0.13
0.03
Temperature (°C)
20
30
20
30
20
Rate of photosynthesis (arbitrary unit)
90
90
195
275
90
Carbon dioxide concentration (%)
Which of the following are probably the limiting factors of the rate of
photosynthesis under conditions P and R?
A
B
C
D
P
temperature
light intensity
carbon dioxide concentration
carbon dioxide concentration
R
light intensity
temperature
temperature
carbon dioxide concentration
C
--------------------------------------------------© Oxford University Press
21-4
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143480]
* Directions: The following two questions refer to the diagram below, which
shows a set-up used to study photosynthesis.
dilute sodium
hydrogencarbonate
solution
bench
lamp
2m
Hydrilla
Dilute sodium hydrogencarbonate solution was used to
(1) supply Hydrilla with enough carbon dioxide.
(2) adjust the water to an optimum pH.
(3) provide Hydrilla with the minerals necessary for photosynthesis.
A
B
C
D
(1) only
(2) only
(1) and (2) only
(1), (2) and (3)
A
--------------------------------------------------[10143482]
* If light intensity was the factor limiting the rate of photosynthesis during the
experiment, which of the following changes would increase the rate in which gas
bubbles given off by Hydrilla?
A
B
Move the bench lamp to a place 1 m from the beaker.
Move the bench lamp to a place 4 m from the beaker.
C
D
Raise the temperature of the solution in the beaker by 10 °C.
Double the concentration of the sodium hydrogencarbonate solution.
A
---------------------------------------------------
© Oxford University Press
21-5
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143499]
**Chloroplasts extracted from plant cells were suspended in DCPIP solution and
illuminated, as shown in the diagram below. Blue DCPIP solution decolourizes
when it is reduced.
light
chloroplasts suspended in
blue DCPIP solution
The DCPIP solution decolourized after 15 minutes because
A
B
C
D
oxygen was released during photolysis of water.
hydrogen was produced during photolysis of water.
ATP was formed during photophosphorylation.
carbon dioxide was reduced.
B
--------------------------------------------------[10143511]
* Which of the following chemicals are not available for the Calvin cycle of
photosynthesis when a plant is kept in the dark?
(1) ATP
(2) NADPH
(3) carbon dioxide
A
(1) and (2) only
B
C
D
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
A
---------------------------------------------------
© Oxford University Press
21-6
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143516]
* The diagram below shows some tissues in the vein of a green leaf.
X
Tissue X contributes to photosynthesis of the leaf by
(1) carrying water to the leaf for photosynthesis.
(2) avoiding accumulation of photosynthetic products in the leaf by carrying
them away.
(3) supporting and spreading the leaf blade to receive as much sunlight as
possible.
A
B
C
D
(1) only
(2) only
(1) and (3) only
(1), (2) and (3)
C
--------------------------------------------------[10143523]
 Which of the following is not produced in the Calvin cycle of photosynthesis?
A
B
C
D
ADP
NADP
triose phosphate
oxygen
D
---------------------------------------------------
© Oxford University Press
21-7
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143535]
 The diagram below shows the Calvin cycle of photosynthesis.
X
3-C compound
5-C compound
Y
starch
What are X and Y?
A
B
C
D
X
light energy
carbon dioxide
carbon dioxide
triose phosphate
Y
oxygen
NADPH
glucose
glucose
C
--------------------------------------------------[10143544]
* Which of the following are the uses of energy released from excited electrons in
photochemical reactions of photosynthesis?
(1) synthesis of ATP
(2) reduction of NADP
(3) photolysis of water
A
(1) and (2) only
B
C
D
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
B
---------------------------------------------------
© Oxford University Press
21-8
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143550]
* Which of the following factors affect the rate of photochemical reactions of
photosynthesis?
(1) carbon dioxide concentration
(2) light intensity
(3) water supply
A
B
C
D
(1) and (2) only
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
C
--------------------------------------------------[10143556]
* The diagram below shows an organelle.
outer
membrane
inner
membrane
stacks of
membranous
sacs
Which of the following cells contain the above organelle?
(1) leaf mesophyll cell of rice
(2) cell in a potato tuber
(3) green algal cell
A
(1) and (2) only
B
C
D
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
B
---------------------------------------------------
© Oxford University Press
21-9
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143578]
* The graph below shows the amounts of carbon dioxide absorbed by a green plant
under different light intensities.
amount of
carbon dioxide
absorbed
(arbitrary unit)
R
0
light intensity
(arbitrary unit)
Q
P
According to the graph above, which of the following statements is/are correct?
(1) At point P, the rate of photosynthesis is limited by light intensity.
(2) At point Q, the rate of photosynthesis is zero.
(3) At point R, the rate of photosynthesis is limited by factors other than light
intensity.
A
B
C
(1) only
(2) only
(1) and (3) only
D
(1), (2) and (3)
C
--------------------------------------------------[10143584]
* Some processes in photosynthesis are listed below.
X: NADP is reduced to form NADPH.
Y: Triose phosphate combines to form glucose.
Z: Carbon dioxide combines with a 5-C compound.
Which of the following is the correct sequence of these processes?
A
B
C
D
X, Y, Z
X, Z, Y
Y, X, Z
Z, X, Y
B
--------------------------------------------------© Oxford University Press
21-10
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143591]
 A leaf picked from a destarched plant was covered with aluminium foil as shown
in the diagram below. The leaf was exposed to sunlight for 8 hours and tested for
starch afterwards.
aluminium
foil
exposed to
sunlight for
8 hours
hole in
aluminium
foil
W
X
Y
Z
In which region(s) was starch found?
A
B
C
D
Y only
W and Z only
W, X and Z only
W, X, Y and Z
C
--------------------------------------------------[10143614]
* In photosynthesis, how many water and carbon dioxide molecules are needed to
produce one glucose molecule?
A
B
Number of water
molecules
12
6
Number of carbon
dioxide molecules
12
6
C
D
12
6
6
12
B
---------------------------------------------------
© Oxford University Press
21-11
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143628]
 The diagram below shows the Calvin cycle of photosynthesis.
carbon dioxide
X
Y
Z
glucose
Which of the following correctly shows the numbers of carbon atoms of
compounds X, Y and Z?
A
X
5
Y
6
Z
3
B
C
D
5
3
5
3
3
3
6
5
3
D
--------------------------------------------------[10143637]
 Which of the following statements about photosynthesis is not correct?
A
Oxygen is released during photosynthesis.
B
C
D
Photosynthesis occurs in chloroplasts.
All stages of photosynthesis require light.
Organic substances are made from carbon dioxide and water during
photosynthesis.
C
---------------------------------------------------
© Oxford University Press
21-12
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143642]
* Directions: The following two questions refer to the graph below, which shows
three curves (I, II and III) representing the rates of oxygen production of three
plants, X, Y and Z, on a sunny day. The three plants were put under different
conditions as shown in the table below.
Plant
Condition
X
In a greenhouse with 3% carbon dioxide
Y
In a greenhouse with 0.03% carbon dioxide (same concentration
as in the atmosphere)
Z
In a shaded area
I
T
rate of
oxygen
production
II
III
4:00
8:00
12:00 16:00 20:00
time of the day
0:00
Which plant does curve I represent?
A
B
C
D
X
Y
Z
cannot be determined
A
--------------------------------------------------[10143643]
* In the time period T, which factor was limiting the rate of photosynthesis of the
plant represented by curve II?
A
B
C
D
light intensity
water supply
amount of chlorophyll
carbon dioxide concentration
D
--------------------------------------------------© Oxford University Press
21-13
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143645]
* The photograph below shows a plant. After destarching, the plant was exposed to
sunlight for several hours. A leaf was then picked and tested for starch. The
results show that starch was present in the green part but not in the white part of
the leaf.
green part
white part
What conclusion can be drawn from the results?
A
B
Carbon dioxide is necessary for the formation of starch.
The hypothesis that starch is formed in the green part of the leaf is
supported.
C
D
An enzyme present in the white part of the leaf destroys the starch formed.
Carbohydrates are transported from the white part to the green part of the
leaf.
B
--------------------------------------------------[10143651]
 Which of the following statements about chlorophyll are correct?
(1) It is green in colour.
(2) It is consumed during photosynthesis.
(3) It captures light energy.
A
(1) and (2) only
B
C
D
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
B
---------------------------------------------------
© Oxford University Press
21-14
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143652]
* The diagram below shows a set-up used to investigate the effect of light intensity
on photosynthesis. The bench lamp is switched on and the set-up is left at room
temperature for half a day.
gas X
dilute sodium
hydrogencarbonate
solution
bench
lamp
Hydrilla
Which of the following statements about gas X is not correct?
A
B
Gas X is produced in the photochemical reactions.
Less gas X will be collected if Hydrilla is placed further away from the
lamp.
C
D
Gas X is produced from the splitting of carbon dioxide molecules.
Gas X can relight a glowing splint.
C
--------------------------------------------------[10143654]
 Which of the following is/are required in an investigation of the need for
chlorophyll in photosynthesis?
(1) potassium hydroxide pellets
(2) black paper masks
(3) a plant with variegated leaves
A
(1) only
B
C
D
(2) only
(3) only
(1) and (2) only
C
---------------------------------------------------
© Oxford University Press
21-15
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143656]
 Which of the following is the stage of photosynthesis in which carbon dioxide is
fixed?
A
B
C
D
photophosphorylation
the Calvin cycle
photolysis of water
photochemical reactions
B
--------------------------------------------------[10143682]
 Directions: The following two questions refer to the set-up below, which was
used to investigate the effect of light intensity on the rate of photosynthesis.
Light intensity was varied by placing the bench lamp at different distances from
Hydrilla. The rate of photosynthesis was calculated from the change in the
position of the meniscus in the pipette.
bench
lamp
water
solution X
Hydrilla
What is solution X and what is the purpose of using it?
A
B
C
D
Solution X
distilled water
glucose solution
dilute sodium
hydrogencarbonate solution
potassium hydroxide solution
Purpose
to provide a bacteria-free medium
to supply Hydrilla with food
to supply Hydrilla with carbon dioxide
to absorb carbon dioxide released
C
---------------------------------------------------
© Oxford University Press
21-16
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143693]
 Which of the following shows the result of this experiment?
A
B
The rate of photosynthesis decreases as the light intensity increases.
The increase in the rate of photosynthesis stops after the light intensity has
reached the saturation point.
C
The rate of photosynthesis increases rapidly after the saturation point is
reached.
D
The rate of photosynthesis does not change under different light intensities.
B
--------------------------------------------------[10143698]
 The diagram below shows the transverse section of a dicotyledonous leaf.
X
Y
Z
Which of the labelled cells can carry out photosynthesis?
A
X only
B
C
D
Y only
X and Y only
Y and Z only
D
---------------------------------------------------
© Oxford University Press
21-17
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143708]
* Directions: The following two questions refer to the set-up below, which was
used to investigate the need for carbon dioxide in photosynthesis. The set-up was
placed under strong sunlight for 8 hours.
leaf P
leaf Q
pellet X
What is pellet X?
A
B
C
D
carbon
sulphur
sodium chloride
potassium hydroxide
D
--------------------------------------------------[10143720]
* After 8 hours, iodine solution was used to test for the presence of starch. The
iodine solution turned blue-black in both leaves. Which of the following is a
possible explanation for the results?
A
B
An 8-hour exposure under strong sunlight was too long.
A plant with variegated leaves was not used in this experiment.
C
The plant was not put in the dark for at least 24 hours before the
experiment.
D
The whole set-up was not put in a vacuum container.
C
---------------------------------------------------
© Oxford University Press
21-18
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143725]
 Directions: The following two questions refer to the photograph below, which
shows a variegated leaf. Parts X and Y are white and green respectively.
X (white)
Y (green)
Which of the following organelles are present in the cells of part Y but not in the
cells of part X?
A
B
C
nuclei
chloroplasts
mitochondria
D
vacuoles
B
--------------------------------------------------[10143731]
 Why are the organelles stated in the above question important for
photosynthesis?
A
B
They release energy from food to drive the process.
They possess a pigment to capture light energy.
C
D
They carry genetic information to control cellular activities.
They store water which is essential for photosynthesis.
B
---------------------------------------------------
© Oxford University Press
21-19
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143735]
 In the Calvin cycle of photosynthesis, which of the following substances is/are
used?
A
B
C
D
NADPH and ATP
water and oxygen
chlorophyll
oxygen and triose phosphate
A
--------------------------------------------------[10143751]
 Which of the following is/are the outcome(s) of photosynthesis?
(1) Oxygen concentration in the atmosphere is increased.
(2) Hydrogen concentration in the atmosphere is reduced.
(3) Glucose and other nutrients are synthesized.
A
B
C
D
(1) only
(2) only
(1) and (3) only
(1), (2) and (3)
C
--------------------------------------------------[10143770]
 Which of the following leaf cells can carry out photosynthesis?
(1) palisade mesophyll cell
(2) spongy mesophyll cell
(3) epidermal cell
A
B
C
(1) only
(3) only
(1) and (2) only
D
(1), (2) and (3)
C
---------------------------------------------------
© Oxford University Press
21-20
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143777]
 What are the advantages of growing crops in a greenhouse?
(1) better humidity control
(2) attracting insects for pollination
(3) better temperature control
A
B
C
D
(1) and (2) only
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
B
--------------------------------------------------[10143780]
 The starch stored in the leaves of a plant can be removed most effectively by
putting the plant
A
B
C
D
in hot water.
under bright light.
under dim light.
in the dark.
D
--------------------------------------------------[10143790]
 Which of the following substances pass in and out of the leaves through the
stomata?
(1) carbon dioxide
(2) oxygen
(3) water vapour
A
B
(1) and (2) only
(1) and (3) only
C
D
(2) and (3) only
(1), (2) and (3)
D
---------------------------------------------------
© Oxford University Press
21-21
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143796]
* Which of the following is most probably the factor limiting the rate of
photosynthesis of the crops in a well-watered field on a hot, sunny day?
A
B
C
D
light intensity
carbon dioxide concentration
availability of water
temperature
B
--------------------------------------------------[10143800]
 Which of the following substances can be synthesized from triose phosphate for
making cell wall?
A
B
C
D
glycerol
proteins
cellulose
fatty acids
C
--------------------------------------------------[10143823]
 Leaf is the main organ for
A
B
C
D
the transport of food.
photosynthesis.
excretion.
the storage of food.
B
--------------------------------------------------[10143831]
 Water is transported to the leaf for photosynthesis by
A
B
C
D
the stoma.
the phloem.
the xylem.
the epidermis.
C
---------------------------------------------------
© Oxford University Press
21-22
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143842]
* Under which of the following conditions is the rate of photosynthesis the
highest?
A
B
C
D
dim light, 20 °C and 0.03% CO2
bright light, 20 °C and 0.03% CO2
bright light, 20 °C and 0.01% CO2
bright light, 15 °C and 0.03% CO2
B
--------------------------------------------------[10143843]
* Which of the following occurs in the Calvin cycle of photosynthesis?
A
B
C
D
release of oxygen
absorption of light by chlorophyll
oxidation of NADPH
formation of ATP
C
--------------------------------------------------[10143849]
* Which of the following statements about photosynthesis is correct?
A
Photochemical reactions occur only in the presence of light and the Calvin
cycle occurs only in the absence of light.
B
C
D
Chlorophyll will be consumed during photosynthesis.
Photosynthesis involves a series of reactions catalysed by enzymes.
Photosynthesis can produce energy for the plants.
C
--------------------------------------------------[10143862]
 The raw materials required for photosynthesis are
A
B
C
D
carbon dioxide and oxygen.
carbon dioxide and water.
carbon dioxide, water and minerals.
carbon dioxide, water, minerals and chlorophyll.
B
---------------------------------------------------
© Oxford University Press
21-23
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143865]
* Which of the following statements about photosynthesis is not correct?
A
B
C
D
It occurs in all plant cells.
Some of the reactions involved in the process are catalysed by enzymes.
Light energy is converted into chemical energy in the process.
It allows an input of energy to ecosystems.
A
--------------------------------------------------[10143884]
* Destarching of plants is not needed when
A
B
C
D
we investigate the kind of gas released during photosynthesis.
we investigate the need for light in photosynthesis.
we investigate the need for carbon dioxide in photosynthesis.
we investigate the need for water in photosynthesis.
A
--------------------------------------------------[10143886]
 Photolysis of water in photochemical reactions refers to
A
the formation of water molecules in the presence of light.
B
C
D
the splitting of water molecules into hydrogen and oxygen.
the release of water vapour during photosynthesis.
the absorption of water molecules by chlorophyll molecules during
photosynthesis.
B
--------------------------------------------------[10143892]
 Which of the following statements about the Calvin cycle of photosynthesis is
correct?
A
B
C
D
The Calvin cycle does not require light.
The Calvin cycle occurs only in the absence of light.
Oxygen is produced as a by-product in the Calvin cycle.
Water and carbon dioxide combine to form glucose in the Calvin cycle.
A
---------------------------------------------------
© Oxford University Press
21-24
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143899]
 Photosynthetic products are used by plants in the synthesis of
(1) amino acids.
(2) cellulose.
(3) glycerol and fatty acids.
A
B
C
D
(2) only
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
D
--------------------------------------------------[10143900]
 The photograph below shows a building.
Growing crops in this building can increase crop yield. It is because
(1) the carbon dioxide concentration inside the building can be increased.
(2) the building can protect the crops from being damaged by insects.
(3) a constant temperature can be kept inside the building.
A
(1) only
B
C
D
(1) and (2) only
(2) and (3) only
(1), (2) and (3)
D
---------------------------------------------------
© Oxford University Press
21-25
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143902]
 Directions: The following two questions refer to the diagram below, which
shows the structure of a dicotyledonous leaf.
P
Q
R
S
Which layer of cells contains the highest density of chloroplasts?
A
P
B
C
D
Q
R
S
B
--------------------------------------------------[10143906]
 Which of the following statements is not correct?
A
Layer Q is on the upper side of the leaf which allows effective absorption of
sunlight.
B
C
D
Layer R contains tissue that transports water to the leaf.
There are many air spaces in layer R.
No photosynthesis occurs in layer S.
D
---------------------------------------------------
© Oxford University Press
21-26
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Multiple-choice questions
[10143912]
 In the leaves of dicotyledonous plants, what is glucose converted to for storage?
A
B
C
D
glycogen
maltose
sucrose
starch
D
---------------------------------------------------
© Oxford University Press
21-27
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Short questions
Short questions
[10144083]
**A scientist used a unicellular alga to study photosynthesis. The graph below
shows the changes in the amounts of a 3-C compound and a 5-C compound
produced in the Calvin cycle before and after light was switched off in an
experiment. All other conditions were kept constant.
light switched off
light
amount of
compounds
dark
3-C compound
5-C compound
0
1
2
time (minute)
3
4
a
Account for the changes in the amounts of the 3-C compound and the 5-C
compound when the light was on.
(4 marks)
b
Account for the changes in the amounts of the 3-C compound and the 5-C
compound after the light was switched off.
(2 marks)
-- answer -a
When light was on, NADPH and ATP were produced in the photochemical
reactions.
1m
In the presence of NADPH and ATP, the 3-C compound was reduced to triose
phosphate continuously. On the other hand, the 3-C compound was produced
continuously by combining 5-C compounds with carbon dioxide.
© Oxford University Press
21-28
1m
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Short questions
In the presence of NADPH and ATP, the 5-C compound was regenerated
continuously by using some of the triose phosphate. On the other hand, the 5-C
compounds continuously combined with carbon dioxide to produce the 3-C
compound.
1m
As a result, the amounts of the 3-C compounds and the 5-C compounds remained
constant.
b
1m
Without NADPH and ATP from photochemical reactions, triose phosphate could
not be formed from the 3-C compound, therefore the 3-C compound accumulated.
1m
Without triose phosphate, the 5-C compound could not be regenerated. Therefore
the amount of the 5-C compound decreased.
1m
--------------------------------------------------[10144115]
* a
b
i
Name the two products produced in photochemical reactions of
photosynthesis which are used in the Calvin cycle.
(1 mark)
ii Describe how each product is used in the Calvin cycle.
(2 marks)
A photosynthetic bacterium carries out photosynthesis that is different from
that in green plants. The equation for the process of photosynthesis in this
bacterium is shown below.
hydrogen
carbon
+
sulphide
dioxide
light captured
by bacterial
chlorophyll
carbohydrates + sulphur + water
What is the function of hydrogen sulphide in photosynthesis?
(2 marks)
-- answer -a
i
ATP and NADPH
1m
ii
ATP provides energy for the reduction of the 3-C compound into triose
phosphate / the regeneration of the 5-C compound.
1m
NADPH provides hydrogen for the reduction of the 3-C compound into triose
phosphate.
b
1m
To donate hydrogen
1m
for the reduction of the 3-C compound into triose phosphate.
1m
---------------------------------------------------
© Oxford University Press
21-29
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Short questions
[10144117]
* The diagram below summarizes reactions that occur in chloroplasts.
light energy
ADP
photochemical
reactions
X
ATP
Y
oxygen
hydrogen
triose phosphate
Calvin cycle
carbon dioxide
a
b
c
5-C compound
glucose
Name X and Y.
(2 marks)
State the parts of chloroplasts where the following stages of photosynthesis
occur.
i
photochemical reactions
(1 mark)
ii the Calvin cycle
(1 mark)
If Y is absent, can ATP still be produced in photosynthesis? Explain your
answer.
(1 mark)
-- answer -a
b
c
X: phosphate
1m
Y: water
1m
i
Thylakoids / grana
1m
ii
Stroma
1m
Without Y, ATP can still be produced in photophosphorylation, but not in the Calvin
cycle.
1m
--------------------------------------------------© Oxford University Press
21-30
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Short questions
[10144130]
**A scientist obtained some chloroplasts from plant cells and separated the stroma
and the grana of the chloroplasts. He then set up the following test tubes, placed
them under light and measured the rate of carbon dioxide uptake in the two test
tubes.
Tube
Contents
Rate of carbon dioxide uptake (arbitrary unit)
X
Stroma
4000
Y
Stroma + grana
96 000
a
Explain why the rate of carbon dioxide uptake in tube X was much lower
than tube Y.
(4 marks)
b
How would the rate of carbon dioxide uptake change if tube Y was put in
the dark?
(1 mark)
-- answer -a
Photochemical reactions of photosynthesis occur in the thylakoids of the grana.
1m
Without grana, photochemical reactions did not occur in tube X. No NADPH and
ATP were produced.
1m
The 3-C compound could not be reduced into triose phosphate and the 5-C
compound could not be regenerated.
1m
Less 5-C compound was present to accept carbon dioxide, thus the rate of carbon
dioxide uptake was much lower.
b
1m
The rate of carbon dioxide uptake would decrease to about 4000 arbitrary units.
1m
--------------------------------------------------[10144134]
* Read the following article and answer the questions.
The use of fossil fuels is increasing. Burning of fossil fuels releases
carbon dioxide into the atmosphere. This increases the atmospheric carbon
dioxide level and leads to problems like global warming and climate change.
Despite the many problems caused, some scientists found that the
increase in carbon dioxide level may increase crop yield.
© Oxford University Press
21-31
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Short questions
a
Explain why an increase in carbon dioxide level may increase crop yield.
(2 marks)
b
State one change caused by global warming that contributes to an increase
in crop yield.
(1 mark)
c
Despite an increase in carbon dioxide level, crop yield in shaded areas does
not change much. Explain why.
(2 marks)
-- answer -a
As carbon dioxide level increases, more substrates are supplied to the Calvin
cycle of photosynthesis.
1m
Therefore, the rate of photosynthesis increases.
1m
b
Increase in temperature
1m
c
In shaded areas, the light intensity is low.
1m
Light intensity is the limiting factor of the rate of photosynthesis. / Carbon dioxide
level is not the limiting factor of the rate of photosynthesis.
1m
--------------------------------------------------[10144138]
 The diagram below shows the structure of a chloroplast.
X
Y
a
b
c
d
Name X and Y.
(2 marks)
Where is chlorophyll located in X?
(1 mark)
Describe how the structure of Y is adapted to photosynthesis.
(2 marks)
Starch grains are usually found in the stroma of chloroplasts. Explain why
starch grains will disappear if the plant is kept in the dark for 1 day.
(2 marks)
© Oxford University Press
21-32
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Short questions
-- answer -a
X: thylakoid
1m
Y: granum
1m
b
On the thylakoid membrane
1m
c
Y contains a large number of thylakoids arranged in stacks. This provides a large
surface area to pack more chlorophyll for absorbing light.
1m
Y is interconnected with other grana by extensions from the thylakoids. This allows
d
efficient transport of photosynthetic products within the chloroplast.
1m
In the dark, photosynthesis stops and no starch will be produced.
1m
Starch grains in the chloroplasts will be converted to sucrose and transported out
of the leaf to other parts of the plant.
1m
--------------------------------------------------[10144145]
 The diagram below shows a set-up that was used to investigate the requirements
for photosynthesis. The leaf was tested for starch using iodine solution after the
set-up was exposed to sunlight for 5 hours.
sunlight
cotton wool
soaked with
soda lime
green leaf
(destarched)
soda lime
a
b
Describe how we can test the leaf for starch.
What was the result of the test? Explain your answer.
(4 marks)
(2 marks)
-- answer -a
Boil the leaf in water for a minute.
1m
Put the leaf into alcohol that is warmed in hot water.
1m
Then transfer the leaf to hot water again.
1m
Add iodine solution onto the surface of the leaf and observe any colour change.
1m
b
The iodine solution remained brown.
1m
Photosynthesis could not occur without carbon dioxide.
1m
---------------------------------------------------
© Oxford University Press
21-33
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Short questions
[10144149]
**A student carried out an experiment to study the effect of light intensity on the
rate of photosynthesis. He cut some discs from several leaves and put the leaf
discs into four beakers of dilute sodium hydrogencarbonate solution. The
beakers were then put at different distances from a bench lamp.
dilute sodium
hydrogencarbonate
solution
leaf disc
Initially all leaf discs sank to the bottom of the beakers, but then they began to
rise to the surface of the solution. The time taken for all the leaf discs in different
beakers to rise to the surface was recorded as follows:
Distance from the lamp (cm)
25
50
75
100
Average time taken (min)
18
25
54
98
a
What is the function of dilute sodium hydrogencarbonate solution in the
experiment?
(1 mark)
b
State two precautions that should be taken when cutting the leaf discs to
ensure the experiment is a fair test.
(2 marks)
c
d
Explain why the leaf discs rose to the surface of the solution.
What can you conclude from the results?
(3 marks)
(1 mark)
-- answer -a
To supply the leaf discs with carbon dioxide for carrying out photosynthesis.
1m
b
c
The leaf discs should be cut from the same plant / same leaf.
1m
The leaf discs should be of the same diameter / surface area.
1m
Under light, the leaf discs carried out photosynthesis.
1m
Oxygen was produced during the process.
1m
The leaf discs became less dense / more buoyant, thus they rose to the surface.
1m
d
The nearer the light source / the greater the light intensity, the higher the rate of
photosynthesis.
1m
---------------------------------------------------
© Oxford University Press
21-34
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Short questions
[10144159]
* A student investigated the need for light in photosynthesis. He used the
following three set-ups.
sunlight
sunlight
dilute sodium
hydrogencarbonate
solution
dilute sodium
hydrogencarbonate
solution
Hydrilla
Y
X
Z
(in the dark)
X and Y were put under sunlight, while Z was kept in the dark. The change in
volume of gas in the test tubes after 1 hour is shown in the table below.
a
b
Set-up
Change in volume of gas (cm3)
X
0
Y
+0.37
Z
–0.04
Explain why the volume of gas in Z decreased.
(1 mark)
Oxygen was produced in Y as Hydrilla carried out photosynthesis.
i
Estimate the rate of photosynthesis in set-up Y (express in cm3 oxygen
produced per hour).
(1 mark)
ii
Describe the process in which oxygen was produced.
(4 marks)
-- answer -a
It was because oxygen was used for respiration of Hydrilla.
b
i
0.37 – (–0.04) = 0.41 cm 3 oxygen per hour
ii
Chlorophyll molecules captured light energy and some electrons of the
chlorophyll molecules were raised to higher energy levels.
1m
1m
1m
Energy was released when the excited electrons passed through the electron
transport chain.
1m
Part of the energy released was used to split water molecules into hydrogen
and oxygen (photolysis of water).
1m
Oxygen was released as a gas.
1m
--------------------------------------------------© Oxford University Press
21-35
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Short questions
[10144160]
* The diagram below shows the first stage of photosynthesis.
electron
water
excitation
electron
transport
chain
energy
hydrogen + oxygen
light
chlorophyll
a
Where precisely in the chloroplast do the above reactions take place?
(1 mark)
b
c
What is the electron transport chain composed of?
(1 mark)
Energy in the excited electrons is released when the excited electrons pass
through the electron transport chain. Some of the energy released is used to
split water molecules. State another use of the energy.
(1 mark)
d
Water molecules are split into hydrogen and oxygen during photosynthesis.
What is the fate of the hydrogen and oxygen produced?
(2 marks)
-- answer -a
In the thylakoids
1m
b
It is composed of a series of electron carriers in the thylakoid membrane.
1m
c
It is used to form ATP in photophosphorylation / used in combining ADP with a
d
phosphate. / It is converted to chemical energy stored in ATP.
1m
Hydrogen is accepted by NADP to form NADPH.
1m
Oxygen is released as a gas to the atmosphere.
1m
---------------------------------------------------
© Oxford University Press
21-36
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Short questions
[10144181]
* The diagram below shows the Calvin cycle of photosynthesis.
5-C compound
3-C compound
glucose
a
triose phosphate
Where precisely in the chloroplast do the above reactions occur?
(1 mark)
b
c
Explain why these reactions are also called dark reactions.
(1 mark)
Add an arrow on the diagram to show where carbon dioxide enters the
cycle.
(1 mark)
d
i
Two chemicals required by the Calvin cycle are produced in
photochemical reactions. What are they?
(2 marks)
ii
State the function of each of the two chemicals stated in i. (2 marks)
-- answer -a
In the stroma
1m
b
They do not require light / can occur in the dark.
1m
c
Arrow marked between the 5-C compound and the 3-C compound
1m
d
i
ATP and NADPH
1m x 2
ii
ATP provides energy for the reduction of the 3-C compound to triose
phosphate and the regeneration of the 5-C compound.
1m
NADPH provides hydrogen for the reduction of the 3-C compound to triose
phosphate.
1m
---------------------------------------------------
© Oxford University Press
21-37
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Short questions
[10144185]
* The graph below shows the rate of photosynthesis of two species of plants (M
and N) under different light intensities.
rate of photosynthesis
P
M
N
light intensity
a
b
The rate of photosynthesis of M levels off when the light intensity reaches
point P.
i
Name point P.
(1 mark)
ii Explain why the rate levels off.
(2 marks)
Which species, M or N, is better adapted to grow indoors? Explain.
(2 marks)
-- answer -a
i
Saturation point
1m
ii
At light intensities higher than the saturation point, light intensity is no longer
the limiting factor for the rate of photosynthesis.
1m
Other factors like carbon dioxide concentration, temperature, amount of
chlorophyll or the amount of enzymes are limiting.
b
1m
N
1m
It reaches its maximum rate of photosynthesis at a lower light intensity.
1m
--------------------------------------------------[10144199]
 Complete the following paragraph with suitable words.
(4 marks)
In photochemical reactions of photosynthesis, a
molecules capture light energy and some electrons are raised to a higher energy
level. Electrons pass through a series of b
of
decreasing energy levels in the electron transport chain and release energy. The
energy released is used to form c
d
molecules.
© Oxford University Press
21-38
and split
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Short questions
-- answer -a
chlorophyll
1m
b
electron carriers
1m
c
ATP
1m
d
water
1m
--------------------------------------------------[10144220]
* A farmer was thinking of increasing the yield of his crops so he put a
coal-burning stove in one of his two greenhouses. The rates of photosynthesis of
the crops in the two greenhouses were measured on a sunny day in June. The
graph below shows the results.
rate of
photosynthesis
greenhouse
without stove
greenhouse
with stove
a
Explain, with two reasons, why the rate of photosynthesis of the crops in
the greenhouse with the stove was higher.
(4 marks)
b
The farmer put a stove in his greenhouses again in March of the following
year. He found that the increase in the rate of photosynthesis of the crops
was not significant. Explain why.
(2 marks)
-- answer -a
b
The burning of coal increased the temperature.
1m
The activities of the enzymes involved in photosynthesis were higher.
1m
The burning of coal also produced carbon dioxide.
1m
More substrates were supplied to the Calvin cycle.
1m
Other factors like light intensity became a limiting factor.
1m
The increase in temperature and carbon dioxide concentration could no longer
increase the rate of photosynthesis.
1m
--------------------------------------------------© Oxford University Press
21-39
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Short questions
[10144224]
 The diagram below shows two set-ups, which were used to study photosynthesis.
The set-ups were placed in bright light for 6 hours.
lids sealed
with vaseline
leaves
gas jars
cotton wool with
dilute sodium
hydrogencarbonate
solution
cotton wool
with dilute
sodium
hydroxide
solution
water
Set-up X
Set-up Y
a
b
c
What is the aim of this experiment?
(1 mark)
What is the purpose of sealing the lids with vaseline?
(1 mark)
What are the uses of dilute sodium hydrogencarbonate solution and dilute
sodium hydroxide solution in the experiment?
(2 marks)
d
Before picking the leaves from a plant for this experiment, the plant was
destarched.
e
i
Describe how the plant can be destarched.
(1 mark)
ii Why is this step essential?
(1 mark)
After 6 hours, an iodine test was carried out on the two leaves. Which leaf
gave a positive result?
(1 mark)
-- answer -a
To show that carbon dioxide is needed in photosynthesis.
1m
b
To make the gas jars airtight.
1m
c
Dilute sodium hydrogencarbonate solution supplies the leaf with carbon dioxide to
d
carry out photosynthesis.
1m
Dilute sodium hydroxide solution absorbs carbon dioxide in the gas jar.
1m
i
Put the plant in the dark for at least 24 hours.
1m
ii
Destarching removes all the starch in the leaves so that any starch that is
present in the leaves at the end of the experiment is newly made.
e
The leaf in set-up X
1m
1m
--------------------------------------------------© Oxford University Press
21-40
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Structured questions
Structured questions
[10144319]
* A student carried out an experiment to investigate the effect of light intensity on
the rate of photosynthesis in an aquatic plant, using the apparatus shown in the
diagram below.
v
barrel of syringe
plastic tube
board
plunger of syringe
lamp
scale
capillary tube
aquatic plant
test tube
d
The student decided to measure the rate of photosynthesis by measuring the gas
produced over a 5-minute period. The gas was collected in the capillary tube.
After 5 minutes, the length of the bubble was measured along the scale.
The light intensity was varied by altering the distance (d) between the lamp and
the photosynthesizing plant.
The student prepared the table below to calculate the light intensity.
Distance (d) from lamp to plant (cm)
Light intensity (1/d2)
4
0.0625
8
0.0156
12
0.0069
16
0.0039
20
0.0025
24
60
© Oxford University Press
0.0003
21-41
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
a
b
Chapter 21
Structured questions
i
Calculate the light intensity when the lamp was 24 cm from the plant.
Show your working.
(2 marks)
ii
The length of the gas bubble was measured (in mm).
State what additional information would be required to calculate the
volume of gas produced.
(1 mark)
iii
Suggest how the student supplied the aquatic plant with a source of
carbon dioxide.
(1 mark)
Certain assumptions are made when using the apparatus shown in the
diagram to measure the rate of photosynthesis.
i
One of these assumptions is that all of the oxygen produced by the
plant during photosynthesis is collected.
Suggest why not all of the oxygen produced by the plant is collected.
(2 marks)
ii
Another assumption is that all of the gas collected is oxygen.
Analysis of the gas collected reveals that it has the following
composition.
• oxygen 50%
• nitrogen 44%
• carbon dioxide 6%
Suggest a reason for the presence of nitrogen in the gas collected.
(1 mark)
iii
Comment on the percentage of carbon dioxide present in the gas
collected and give reasons for this figure.
(3 marks)
OCR GCE (A) Communication, Homeostasis and Energy Jun 2011 Q2a, b
-- answer -a
i
ii
1 / 242
1m
= 0.0017
1m
Internal radius / diameter / cross-sectional area of the capillary tube
1m
iii
Use sodium hydrogencarbonate solution. /
Bubble carbon dioxide into the tube.
b
i
1m
Some oxygen dissolves in water. /
Some oxygen is used in respiration. /
Some oxygen may escape from the collection apparatus. /
Some oxygen is trapped in the bubble attached to the leaf / in the air spaces
of the leaf. (any 2)
ii
1m x 2
Nitrogen is present in the air spaces of the leaf. /
Some nitrogen comes out of the solution.
© Oxford University Press
21-42
1m
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
iii
Chapter 21
Structured questions
The percentage of carbon dioxide is higher than that in the atmosphere. /
The plant produces carbon dioxide during respiration. /
Carbon dioxide that has been added to the solution comes out of it. /
The percentage is lower than the actual value as some of the carbon dioxide
dissolves in the solution / is used in photosynthesis. (any 3)
1m x 3
--------------------------------------------------[10144322]
* The graph below shows the effects of carbon dioxide concentration, light
intensity and temperature on the rate of photosynthesis of a crop plant.
0.12% CO2 at 20 °C
0.03% CO2 at 30 °C
rate of
photosynthesis
0.03% CO2 at 20 °C
X
0
1
2
3
4
light intensity (kilolux)
a
Which factor is limiting the rate of photosynthesis at point X? Explain your
answer.
(2 marks)
b
In a greenhouse in winter, the mean carbon dioxide concentration is 0.03%,
the temperature is 20 °C and the light intensity is 3 kilolux. Using the graph,
describe the effects of each of the following changes on the rate of
photosynthesis. How will the following changes affect the growth of the
crop plants? Explain briefly.
c
d
i
The carbon dioxide concentration is increased to 0.12%.
ii The temperature is increased to 30 °C.
(4 marks)
Explain why it is not advisable to increase the temperature in a greenhouse
on a dull winter day.
(2 marks)
Even under optimum conditions, only a relative small percentage of the
sunlight falling on the leaves of a plant grown in a greenhouse is used for
photosynthesis. Give two reasons.
(2 marks)
© Oxford University Press
21-43
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Structured questions
-- answer -a
b
Light intensity
1m
When light intensity increases, the rate of photosynthesis increases.
1m
i
An increase of carbon dioxide from 0.03% to 0.12% will nearly double the
rate of photosynthesis.
1m
This is because at higher carbon dioxide concentration, more substrates are
supplied to the Calvin cycle.
ii
1m
Increasing the temperature from 20 °C to 30 °C will not affect the rate of
photosynthesis.
1m
This is because temperature is not the limiting factor of the rate of
photosynthesis under such conditions.
c
1m
The rate of photosynthesis is limited by light intensity or carbon dioxide
concentration on a dull winter day.
1m
Increasing temperature will not increase the rate of photosynthesis but increase
the rate of respiration. The net production of carbohydrates may decrease. 1m
d
Most of the wavelengths of sunlight are not absorbed by chlorophyll.
1m
Much of the incident light is reflected by the leaf surface.
1m
--------------------------------------------------[10144327]
* A student put the following set-up under sunlight for 5 hours to study a
requirement for photosynthesis.
leaf P
leaf Q
potassium
hydroxide
pellet
potted plant (only
part of it is shown)
a
Before the experiment, the plant was destarched. Describe how it was done
and explain why destarching is important.
(2 marks)
© Oxford University Press
21-44
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Structured questions
b
Which requirement for photosynthesis was studied in this experiment?
(1 mark)
c
Describe how you can carry out a test to determine if photosynthesis has
occurred in leaves P and Q.
(4 marks)
d
e
Describe the results in leaves P and Q after the test in c.
(2 marks)
How can you modify the above set-up to investigate the requirement of
chlorophyll for photosynthesis at the same time?
(1 mark)
-- answer -a
The plant was destarched by putting it in the dark for at least 24 hours.
1m
Destarching removes all the starch in the leaves so that any starch detected in the
leaves at the end of the experiment is made during the experiment.
1m
b
Carbon dioxide
1m
c
Boil the leaves in water for a minute.
1m
Put the leaves into alcohol that is warmed in hot water.
1m
Then transfer the leaves to hot water again.
1m
Add iodine solution onto the surfaces of the leaves and observe any colour
d
e
change.
1m
Leaf P: The iodine solution turned blue-black.
1m
Leaf Q: The iodine solution remained brown.
1m
Replace the plant with a plant with variegated leaves.
1m
--------------------------------------------------[10144332]
 a
b
Write a word equation for photosynthesis.
(2 marks)
The diagram below shows an experimental set-up, which was used to
investigate the effect of light intensity on the rate of photosynthesis. The
beaker was put at different distances from the bench lamp.
dilute sodium
hydrogencarbonate
solution
bench
lamp
Hydrilla
© Oxford University Press
21-45
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Structured questions
The number of gas bubbles released from Hydrilla was recorded. The
results are shown in the table below.
Distance from lamp (cm)
Number of gas bubbles per minute
40
50
80
48
120
38
160
20
200
20
i
ii
Present the results in the form of a graph.
(4 marks)
What would be the number of gas bubbles released in a minute when
the lamp was placed at a position 140 cm from the lamp? (1 mark)
iii
Referring to the results, describe how the rate of photosynthesis of
Hydrilla changes with light intensity.
(2 marks)
iv
Suggest how the set-up can be modified to investigate the effect of
carbon dioxide concentration on the rate of photosynthesis.
(3 marks)
-- answer -a
Carbon dioxide + water → carbohydrates + oxygen
2m
b
i
1m
Correct title
Choice of axes (x-axis: distance from lamp, y-axis: number of gas bubbles
per minute)
1m
With labels and units
1m
Correct plotting and joining of line
1m
ii
29
1m
iii
When the distance between the lamp and the beaker is 40 cm to 160 cm, the
rate of photosynthesis decreases as light intensity decreases.
1m
When the distance between the lamp and the beaker is larger than 160 cm,
the rate of photosynthesis remains the same as light intensity decreases.
1m
iv
Set up a few beakers with the same mass of Hydrilla
1m
but different concentrations of dilute sodium hydrogencarbonate solution.
1m
Put all the beakers under the same light intensity / at the same distance from
the lamp.
1m
--------------------------------------------------© Oxford University Press
21-46
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Structured questions
[10144348]
* a
The Calvin cycle of photosynthesis is outlined below.
carbon dioxide
5-C compound
3-C compound
compound P
b
i
Name compound P.
(1 mark)
ii How is glucose formed in the Calvin cycle?
(1 mark)
The table below shows the rate of the Calvin cycle of a plant at different
temperature.
Temperature (°C)
Rate of the Calvin cycle (arbitrary unit)
5
1.8
15
4.0
25
2.4
35
0.0
It is known that reactions in the Calvin cycle are controlled by enzymes.
i
Explain why the rate of the Calvin cycle increases when the
temperature increases from 5 °C to 15 °C.
(3 marks)
ii
Explain why the rate of the Calvin cycle decreases when the
temperature increases from 15 °C to 35 °C.
(1 mark)
iii
A student concluded from the above data that the rate of the Calvin
cycle doubles as the temperature increases by every 10 °C.
Comment on the student’s conclusion.
(3 marks)
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Chapter 21
Structured questions
-- answer -a
i
Triose phosphate
1m
ii
Two molecules of triose phosphate combine to form a molecule of glucose.
1m
b
i
As temperature increases from 5 °C to 15 °C, the enzyme and substrate
molecules involved in the Calvin cycle have more kinetic energy
1m
and collide with each other more frequently.
1m
This increases the chance of forming enzyme-substrate complexes, thus the
rate of the Calvin cycle increases.
ii
iii
1m
At temperature above 15 °C, the enzymes involved in the Calvin cycle are
denatured.
1m
The student’s conclusion is not correct.
1m
The rate of the Calvin cycle doubles only when temperature increases from
5 °C to 15 °C,
1m
but not for any temperature higher than 15 °C.
1m
--------------------------------------------------[10144350]
* The diagram below shows a set-up. A student used the set-up to investigate the
effect of light intensity on the rate of photosynthesis by changing the distance
between the bench lamp and the beaker.
rubber tubing
clip
pipette
dilute sodium
hydrogencarbonate
solution
water
bench
lamp
Hydrilla
thermometer
The student first placed the lamp at a distance of 0.8 m from the beaker. He
waited for 5 minutes and recorded the initial liquid level in the pipette. He then
waited for another 5 minutes and recorded the final liquid level. The volume of
gas produced per hour was calculated. The results are shown in the table below.
© Oxford University Press
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Chapter 21
Structured questions
Distance from lamp (m)
Volume of gas produced per hour (mm3)
0.8
20
0.7
28
0.6
37
0.5
47
0.4
53
0.3
54
0.2
54
0.1
53
a
Why did the student wait for 5 minutes after adjusting the distance between
the lamp and the beaker?
(1 mark)
b
c
What is the function of the thermometer in the set-up?
(1 mark)
i
Plot a graph to show the effect of light intensity on the rate of
photosynthesis.
(4 marks)
d
ii
Over what distance between the beaker and the lamp is light intensity
the limiting factor?
(1 mark)
iii
Sketch on the graph the expected result of another set-up with higher
concentration of sodium hydrogencarbonate solution.
(2 marks)
Describe how you would modify the above set-up to investigate the effect
of the wavelength of light on the rate of photosynthesis.
(1 mark)
-- answer -a
To allow the rate of photosynthesis to become steady.
b
It is used to monitor the temperature of the set-up, as the temperature should be
c
1m
kept constant during the experiment.
1m
i
1m
Correct title
Choice of axes (x-axis: 1/distance from lamp, y-axis: volume of gas produced
per hour)
1m
With labels and units
1m
Correct plotting and joining of line
1m
ii
0.4 m or longer
1m
iii
The curve has the same slope as the one in i at low light intensities.
1m
The curve levels off at a larger volume of gas produced per hour at high light
intensities.
d
1m
Insert filters of different colours between the lamp and the beaker.
1m
--------------------------------------------------© Oxford University Press
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Question Bank
Chapter 21
Structured questions
[10144352]
**A scientist carried out an experiment to determine which colour of light was
most effective for photosynthesis. He placed some Spirogyra (a green alga) in a
suspension of aerobic bacteria and exposed different regions of Spirogyra to red,
green and blue light of the same intensity respectively.
Spirogyra
red light
chloroplast
aerobic bacterium
green light
blue light
He observed and recorded the relative amounts of bacteria attracted to the
regions of Spirogyra exposed to different colour of light. The results are shown
in the table below.
Colour of light
Relative amounts of bacteria (maximum 5+)
Red
++++
Green
+
Blue
++++
(Key: ‘+’ means that there are bacteria attaching to that region. The larger the number of
‘+’, the more the bacteria attached.)
a
Explain why the bacteria attached to Spirogyra when light shone on
Spirogyra.
(2 marks)
b
Explain why the amounts of bacteria attaching to different regions of
Spirogyra were not the same.
(2 marks)
c
What conclusion can be drawn from the above results?
d
Describe how the light energy captured by the pigment in the chloroplasts is
used in photochemical reactions.
(4 marks)
(2 marks)
-- answer -a
Spirogyra carried out photosynthesis when light shone on it. Oxygen was
produced as a by-product.
1m
Aerobic bacteria were attracted by oxygen, thus they attached to the Spirogyra.
1m
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Question Bank
b
Chapter 21
Structured questions
Spirogyra carried out photosynthesis at different rates under different colour of
light.
1m
Aerobic bacteria moved to the regions with higher oxygen concentrations, thus the
c
d
amounts of bacteria were different in different regions.
1m
Photosynthesis occurs at similar rate under blue and red light.
1m
Photosynthesis occurs at a much lower rate under green light.
1m
Chlorophyll molecules capture light energy and some electrons of the chlorophyll
molecules are raised to a higher energy level.
1m
Energy is released when the excited electrons pass through the electron transport
chain.
1m
Some of the energy released is used to form ATP in the process of
photophosphorylation.
1m
Some of the energy released is used to split water molecules into hydrogen and
oxygen (photolysis of water).
1m
--------------------------------------------------[10144359]
**a
Describe how NADPH is formed in the photochemical reactions of
photosynthesis.
(2 marks)
b
In an experiment, the amounts of a 3-C compound and a 5-C compound in
chloroplast-containing cells were measured. Figure 1 shows the effect of
decreasing carbon dioxide concentration on the amounts of the 3-C
compound and the 5-C compound.
high carbon dioxide
concentration
low carbon dioxide
concentration
50
5-C compound
40
amount of
substances 30
(arbitrary unit)
20
3-C compound
10
0
Figure 1
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Question Bank
c
Chapter 21
Structured questions
i
Why was the amount of the 3-C compound twice the amount of the
5-C compound when the carbon dioxide concentration was high?
(2 marks)
ii
Why did the amount of the 5-C compound increase when the carbon
dioxide concentration was low?
(1 mark)
Another experiment was carried out. The same type of cells were put under
light for a period of time and then covered with a light-proof lid. Figure 2
shows the effect of light on the amounts of glucose and the 3-C compound.
light
dark
50
3-C compound
40
amount of
substances 30
(arbitrary unit)
glucose
20
10
0
Figure 2
time
i
Why did the amount of the 3-C compound increase in the dark?
(2 marks)
ii
Why did the amount of glucose decrease in the dark?
(2 marks)
-- answer -a
b
c
NADP accepts hydrogen
1m
which is formed from the splitting of water molecules.
1m
i
In the Calvin cycle, the 5-C compound combined with carbon dioxide 1m
to form two molecules of the 3-C compound.
1m
ii
Less 5-C compound was used as less carbon dioxide was available.
1m
i
Without light, photochemical reactions did not occur. No ATP and NADPH
were formed.
1m
The 3-C compound could not be reduced to triose phosphate, thus it
ii
accumulated.
1m
No glucose was formed in darkness
1m
and some stored glucose was used in respiration.
1m
---------------------------------------------------
© Oxford University Press
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New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Structured questions
[10144360]
* The diagram below shows an experimental set-up.
syringe
gas X
bench
lamp
water
water plant
a
b
What is gas X? How can you test it?
(2 marks)
The experiment was carried out for 10 hours. Sketch a graph to show how
the volume of gas X changed during the experiment.
(2 marks)
c
Explain the graph you have drawn.
(3 marks)
-- answer -a
Oxygen
1m
It relights a glowing splint.
1m
b
volume of
gas X
time
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Question Bank
c
Chapter 21
Structured questions
Correct axes
1m
Correct curve
1m
The volume of gas X first increased rapidly. The rate of photosynthesis was the
highest because light and other factors were abundant.
1m
Then the rate of photosynthesis began to decrease because the carbon dioxide
concentration in the water decreased.
1m
Lastly the increase in the volume of gas X stopped because carbon dioxide was
almost used up.
1m
--------------------------------------------------[10144366]
* The graph below shows three curves (P, Q and R), which represent the rates of
photosynthesis of a crop under different light intensities at three different carbon
dioxide concentrations.
P
Q
rate of
photosynthesis
R
0
1
2
3
4
5
light intensity (arbitrary unit)
a
Which curve, P, Q or R, represents the rate of photosynthesis at the highest
carbon dioxide concentration? Explain briefly.
(3 marks)
b
Mark on the above graph a point at which
i
ii
c
light intensity is limiting the rate of photosynthesis.
(1 mark)
carbon dioxide concentration is limiting the rate of photosynthesis.
(1 mark)
A farmer grows this crop in a greenhouse. He adjusts the carbon dioxide
concentration in the greenhouse to a value same as that of curve P. What
intensity of light should he provide to the crop in order to get a maximum
yield with the lowest cost? Explain.
(3 marks)
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Question Bank
Chapter 21
Structured questions
-- answer -a
P
1m
P levels off at the highest rate of photosynthesis.
1m
At a higher carbon dioxide concentration, more substrates are supplied to the
b
c
Calvin cycle.
1m
i
Any point on the three curves where the rate is increasing
1m
ii
Any point on Q and R where the curves become flat
1m
3 arbitrary units
1m
Light intensity equals the saturation point should be chosen.
1m
It is the lowest light intensity that the crop achieves the highest rate of
photosynthesis, thus giving a highest yield with the lowest cost.
1m
--------------------------------------------------[10144379]
**a
The diagram below shows the Calvin cycle of photosynthesis.
carbon dioxide
5-C compound
ADP + P
ATP
3-C compound
ATP
triose phosphate
ADP + P
i
ATP used in the Calvin cycle is produced in photochemical reactions.
Describe the role of ATP in photosynthesis.
(1 mark)
ii
Another chemical that is produced in photochemical reactions and
used in the Calvin cycle is missing in the above diagram. What is this
chemical? Add (an) arrow(s) on the above diagram to show the
position(s) where this chemical is used.
(2 marks)
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Question Bank
iii
b
Chapter 21
Structured questions
Give the function of the chemical stated in ii in the Calvin cycle.
(1 mark)
The graph below shows the concentrations of the 5-C compound and the
3-C compound in some plant cells before and after a change in the carbon
dioxide concentration at time t.
0.3% CO2
5-C compound
concentration
of compounds
3-C compound
t
time
Suggest whether the carbon dioxide concentration decreased or increased at
time t. Explain your answer.
(4 marks)
-- answer -a
i
ATP transfers energy from the photochemical reactions to the Calvin cycle.
1m
ii
iii
NADPH
1m
Arrow marked between the 3-C compound and triose phosphate
1m
NADPH provides hydrogen for the reduction of the 3-C compound to triose
phosphate.
b
1m
The carbon dioxide concentration decreased at time t.
1m
The concentration of the 5-C compound increased and the concentration of the
3-C compound decreased after the carbon dioxide concentration was changed.
1m
As carbon dioxide concentration decreased, less 5-C compound combined with
carbon dioxide. Thus the concentration of the 5-C compound increased.
1m
Less 3-C compound was formed from the 5-C compound and the conversion of
the existing 3-C compound into triose phosphate continued. Thus the
concentration of the 3-C compound decreased.
1m
---------------------------------------------------
© Oxford University Press
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New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Structured questions
[10144384]
 In an experiment, a well-watered green plant was exposed to sunlight for
5 hours.
sunlight
leaf X
black
paper
a
Which requirement of photosynthesis was investigated in this experiment?
(1 mark)
b
Why is it necessary to destarch the plant before the experiment? How can
the process be carried out?
(2 marks)
c
After the plant was exposed to sunlight, an iodine test was carried out on
leaf X. Draw a diagram to show the results. Label the colours of different
regions.
(2 marks)
d
e
What colours of light are most important for photosynthesis?
Why is chlorophyll green in colour?
(2 marks)
(2 marks)
-- answer -a
Light
1m
b
Destarching removes all the starch in the leaves so that any starch detected in the
leaves at the end of the experiment is made during the experiment.
1m
Destarching can be done by putting the plant in the dark for at least 24 hours.
1m
c
blue-black
brown
Correct drawing
1m
Correct labelling
1m
d
Red, blue
1m x 2
e
Green light is not absorbed
1m
and is reflected.
1m
---------------------------------------------------
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Question Bank
Chapter 21
Structured questions
[10144386]
 The set-up below was left under sunlight. After 10 hours, iodine test was carried
out on leaves X, Y and Z.
leaf Z
black paper
mask
leaf X
leaf Y
plastic bag
potassium
hydroxide solution
a
Why is it necessary to keep the plant in the dark for at least 24 hours before
the experiment?
(1 mark)
b
c
d
What is the use of the potassium hydroxide solution?
Why is the pot enclosed in a plastic bag?
What were the results of the iodine test?
e
Deducing from the results, what are the requirements of photosynthesis?
(2 marks)
(1 mark)
(1 mark)
(3 marks)
-- answer -a
To remove all the starch in the leaves.
1m
b
To absorb carbon dioxide in the jar.
1m
c
To prevent the respiration of soil organisms from affecting the results. 1m
d
Leaf X: The iodine solution turned blue-black except for the masked part, which
e
remained brown.
1m
Leaf Y: The iodine solution remained brown all over the leaf.
1m
Leaf Z: The iodine solution turned blue-black all over the leaf.
1m
Light and carbon dioxide
1m x 2
---------------------------------------------------
© Oxford University Press
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Question Bank
Chapter 21
Structured questions
[10144389]
* An experiment was carried out to investigate the effect of carbon dioxide
concentration on the rate of photosynthesis of a flowering plant. The results are
shown in the table below.
Rate of photosynthesis (arbitrary unit)
CO2 concentration in air
(% volume)
Low light intensity
High light intensity
0
0
0
0.02
20
32
0.04
30
52
0.06
36
69
0.08
40
81
0.12
46
90
0.16
47
95
0.20
47
95
a
b
Present the results as a graph.
(4 marks)
From the graph, find out the rate of photosynthesis at both light intensities
when the carbon dioxide concentration in the air is at normal level.
(2 marks)
c
Describe and explain the results.
d
State how a farmer growing this plant in greenhouses can apply the
information from this investigation to increase yield.
(1 mark)
(3 marks)
-- answer -a
Effect of carbon dioxide concentration in air
on the rate of photosynthesis
100
90
high light intensity
80
70
60
rate of
photosynthesis 50
(arbitrary unit) 40
30
low light intensity
20
10
0
0
0.05
0.1
0.15
0.2
carbon dioxide concentration in air (% volume)
© Oxford University Press
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New Senior Secondary Mastering Biology (Second Edition)
Question Bank
b
c
Chapter 21
Structured questions
Correct title
1m
Choice of axes
1m
With labels and units
1m
Correct plotting and joining of line
1m
When the carbon dioxide concentration is 0.03%, the rate of photosynthesis at
low light intensity: 25 arbitrary units
1m
high light intensity: 42 arbitrary units
1m
The rate of photosynthesis increased with carbon dioxide concentration at both
light intensities because more substrates were supplied to the Calvin cycle. /
The rate of photosynthesis levelled off when the carbon dioxide concentration
reached 0.12% at low light intensity and when the carbon dioxide concentration
reached 0.16% at high light intensity. /
At low light intensity, when the carbon dioxide concentration was higher than
0.12%, the rate of photosynthesis was limited by light intensity. /
At high light intensity, when the carbon dioxide concentration was higher than
0.16%, the rate of photosynthesis was limited by factors other than carbon dioxide
concentration. (any 3)
d
1m x 3
The farmer can increase the yield by adjusting the carbon dioxide concentration
and the light intensity in the greenhouses.
1m
--------------------------------------------------[10144391]
* The diagram below shows a set-up for measuring the rate of photosynthesis of
Hydrilla at 20 °C. Hydrilla was exposed to different light intensities and the rate
of photosynthesis was estimated by counting the number of gas bubbles released
per minute.
dilute sodium
hydrogencarbonate
solution
bench
lamp
gas bubble
Hydrilla
The results are summarized in the table below.
Light intensity
(arbitrary unit)
1
2
3
4
5
6
7
Number of gas bubbles
released per minute
5
8
15
21
23
23
22
© Oxford University Press
21-60
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Structured questions
a
Plot the results on a graph.
(4 marks)
b
c
Describe and explain the results.
(2 marks)
Suggest a method for measuring the rate of photosynthesis that is more
reliable than counting the number of gas bubbles.
(1 mark)
d
How would the rate of photosynthesis differ if the above experiment was
carried out at 4 °C, 30 °C and 60 °C respectively?
(3 marks)
-- answer -a
Effect of light intensity on the rate of photosynthesis
25
20
number of 15
gas bubbles
released per 10
minute
5
0
1
2
3
4
5
6
7
8
light intensity (arbitrary unit)
b
Correct title
1m
Choice of axes
1m
With labels and units
1m
Correct plotting and joining of line
1m
At first, the rate of photosynthesis increased with light intensity because more
energy was supplied to the photochemical reactions.
1m
Then the rate of photosynthesis was limited by other factors such as carbon
dioxide concentration or temperature, therefore the rate became constant. 1m
c
d
Collect the gas released using a graduated tube and record the volume of gas
collected per unit time.
1m
At 4 °C, the rate of photosynthesis would be lower.
1m
At 30 °C, the rate of photosynthesis would be higher.
1m
At 60 °C, the rate of photosynthesis would become zero.
1m
---------------------------------------------------
© Oxford University Press
21-61
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Structured questions
[10144393]
 The diagram below shows a set-up. It was left undisturbed under light for 2 days.
test tube
bench
lamp
hydrogencarbonate
indicator
Hydrilla
a
b
Name the gas released by Hydrilla.
(1 mark)
Suggest one test to verify your answer in a. State the possible result of the
test.
(2 marks)
c
Initially, the hydrogencarbonate indicator was yellow in colour. How would
its colour change during the experiment? Explain your answer. (5 marks)
d
A control similar to the above set-up was kept in the dark for 2 days. What
would be the result? Explain your answer.
(3 marks)
-- answer -a
Oxygen
1m
b
Put a glowing splint over the mouth of the test tube.
1m
Oxygen relights the glowing splint.
1m
The indicator would change from yellow to red,
1m
and then from red to purple.
1m
c
The rate of photosynthesis of Hydrilla was higher than the rate of respiration,
1m
carbon dioxide in the solution was used for photosynthesis.
1m
The decrease in the carbon dioxide concentration caused the colour changes.
1m
d
No gas would be collected in the test tube.
1m
The indicator would remain yellow.
1m
In the dark, only respiration took place. Carbon dioxide released from Hydrilla
would dissolve in the solution.
1m
---------------------------------------------------
© Oxford University Press
21-62
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Structured questions
[10144399]
* The diagram below shows the structure of a greenhouse.
glass roof
reflector
sprinkler
lamp
glass
pane
plants
heater
a
In relation to photosynthesis, why is the greenhouse made of glass?
(2 marks)
b
What is the use of
i
the lamp?
ii the reflector?
c
d
(1 mark)
(1 mark)
In which way can the heater enhance plant growth? Explain.
(4 marks)
Suggest one gas that can be supplied to the greenhouse to enhance plant
growth.
(1 mark)
-- answer -a
b
c
d
Plants require light to carry out photosynthesis.
1m
Glass allows sunlight to reach the plants.
1m
i
To increase the amount of light reaching the plants.
1m
ii
To allow even distribution of light in the greenhouse.
1m
The heater can increase the air temperature in the greenhouse to an optimum
level.
1m
Since photosynthesis involves enzymatic reactions,
1m
increasing temperature can increase the activities of enzymes,
1m
and hence the rate of photosynthesis.
1m
Carbon dioxide
1m
---------------------------------------------------
© Oxford University Press
21-63
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Structured questions
[10144417]
 a
The leaf is the major organ for photosynthesis. Describe how the raw
materials and energy become available to the leaf cells.
(3 marks)
b
How is glucose produced from the primary product of photosynthesis? State
three ways how glucose is used in plants.
(5 marks)
c
Name three types of cells in the leaves which carry out photosynthesis and
three other types of cells which do not.
(2 marks)
-- answer -a
Carbon dioxide from the environment diffuses into the leaf through the stomata.
1m
Water is absorbed from the soil by the roots. It is carried upwards through the
xylem vessels to the leaf.
1m
Light energy is captured by chlorophyll molecules in the leaf cells as it shines on
b
the leaf.
1m
Triose phosphate is the primary product of photosynthesis.
1m
Two molecules of triose phosphate combine to form a glucose molecule.
1m
Glucose can be broken down in the process of respiration to release energy for the
c
use of leaf cells.
1m
Glucose can be built into starch for storage in leaf cells.
1m
Glucose can be used to make other substances like cellulose for growth.
1m
Cells that carry out photosynthesis: palisade mesophyll cells, spongy mesophyll
cells and guard cells
1m
Cells that do not carry out photosynthesis: epidermal cells, xylem cells and phloem
cells
1m
--------------------------------------------------[10144422]
* Photosynthesis occurs in two main stages. The overall reactions occurring in the
two stages are shown below.
Stage 1
Stage 2
© Oxford University Press
water
light
chlorophyll
W+X
Z
X+Y
21-64
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Structured questions
a
Name the two stages of photosynthesis.
(2 marks)
b
c
Identify substances W and Y.
(2 marks)
X produced in stage 1 is accepted by a chemical. What is this chemical?
(1 mark)
d
For each of the following changes in conditions, state which of the two
stages of photosynthesis is affected and how its rate is affected. Explain
your answers.
i
ii
the weather changes from sunny to cloudy
(2 marks)
the atmospheric carbon dioxide concentration increases from 0.03% to
3%
(2 marks)
iii
a decrease in the concentration of magnesium in the soil
(3 marks)
-- answer -a
b
Stage 1: photochemical reactions / light reactions
1m
Stage 2: the Calvin cycle / carbon fixation / dark reactions
1m
W: oxygen
1m
Y: carbon dioxide
1m
c
NADP
d
i
.
The rate of stage 1 decreases.
1m
1m
As light intensity decreases, less energy is supplied to the photochemical
ii
reactions.
1m
The rate of stage 2 increases.
1m
As carbon dioxide concentration increases, more substrates are supplied to
iii
the Calvin cycle.
1m
The rate of stage 1 decreases.
1m
As the concentration of magnesium in the soil decreases, fewer chlorophyll
molecules are produced by the plants.
1m
This reduces the amount of light energy captured, thus less energy is
supplied to the photochemical reactions.
1m
---------------------------------------------------
© Oxford University Press
21-65
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Essays
Essays
[10144489]
* Describe the Calvin cycle of photosynthesis and state the fate of the products.
(10 marks)
-- answer -Process of the Calvin cycle:
The Calvin cycle occurs in the stroma of chloroplasts.
1m
Carbon dioxide combines with a molecule of a 5-C carbon dioxide acceptor to form two
molecules of a 3-C compound.
1m
The 3-C compound is reduced to triose phosphate using energy from ATP and hydrogen
from NADPH produced in photochemical reactions.
1m
Two molecules of triose phosphate combine to form one molecule of glucose.
1m
Some triose phosphate is used to regenerate the 5-C carbon dioxide acceptor using
energy from ATP.
1m
Fate of the products:
Glucose acts as the main energy source. /
Glucose is built into starch, which is stored in leaves. /
Starch is broken down to form sucrose, which is transported by the phloem to other
parts of the plant. /
Glucose is built into cellulose, which is the major component of cell walls. /
The intermediates of photosynthesis can also be used to synthesize glycerol and fatty
acids, which then combine to form lipids. Lipids are used to form cell membranes /
stored as energy reserves. /
The intermediates of photosynthesis can also combine with minerals to form amino
acids, which then combine to form proteins. Proteins are important for growth and
repair / for the synthesis of enzymes / as the components of cell membranes.
(any 2)
1m x 2
Communication
3m
---------------------------------------------------
© Oxford University Press
21-66
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Essays
[10144495]
* What is a ‘limiting factor’? Explain, with one named factor, the effect of the
limiting factor on the rate of photosynthesis.
(10 marks)
-- answer -Meaning of limiting factor:
When a process is affected by more than one factor, its rate is limited by the factor that
is in the shortest supply. This factor is called the limiting factor.
1m
An increase in the value of this factor will lead to an increase in the rate of reaction until
some other factors become limiting.
1m
Effects of limiting factors on the rate of photosynthesis:
Light intensity
1m
At low light intensities, light is a limiting factor.
1m
The rate of photosynthesis increases proportionately with light intensity
1m
as more energy is supplied to the photochemical reactions.
1m
At high light intensities, other factors become limiting.
1m
OR
Carbon dioxide concentration
1m
At low carbon dioxide concentrations, carbon dioxide is a limiting factor.
1m
The rate of photosynthesis increases proportionately with carbon dioxide concentration
1m
because more substrates are supplied to the Calvin cycle.
1m
At high carbon dioxide concentrations, other factors become limiting.
1m
Communication
3m
--------------------------------------------------[10144509]
 Describe how different factors affect the rate of photosynthesis.
(9 marks)
-- answer -At low light intensities, the rate of photosynthesis increases proportionately with light
intensity
1m
as more energy is supplied to the photochemical reactions.
1m
When the light intensity reaches a saturation point, the rate levels off.
1m
At low carbon dioxide concentrations, the rate of photosynthesis increases
proportionately with carbon dioxide concentration
1m
because more substrates are supplied to the Calvin cycle.
1m
The rate levels off as the carbon dioxide concentration reaches a certain point.
1m
Communication
3m
--------------------------------------------------© Oxford University Press
21-67
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Essays
[10144531]
* Describe the process of photosynthesis.
(10 marks)
-- answer -Photosynthesis occurs in two main stages: photochemical reactions and the Calvin
cycle.
1m
The process of photochemical reactions:
The chlorophyll molecules in the thylakoids of chloroplasts capture light energy. /
Some electrons of the chlorophyll molecules are raised to a higher energy level. /
These excited electrons pass through a series of electron carriers (the electron transport
chain) in the thylakoid membrane and release energy gradually. /
Some energy released is used to form ATP by combining a phosphate with ADP
(photophosphorylation). /
Some energy is used to split water molecules to form hydrogen and oxygen. /
Hydrogen is accepted by NADP to form NADPH. /
Oxygen is released as a gas to the atmosphere.
(any 3)
1m x 3
The process of the Calvin cycle:
Carbon dioxide combines with a molecule of a 5-C carbon dioxide acceptor to form two
molecules of a 3-C compound. /
The 3-C compound is reduced into triose phosphate using energy from ATP and
hydrogen from NADPH produced in photochemical reactions. /
Two molecules of triose phosphate combine to form one molecule of glucose. /
Some triose phosphate is used to regenerate the 5-C carbon dioxide acceptor using
energy from ATP.
(any 3)
1m x 3
Communication
3m
---------------------------------------------------
© Oxford University Press
21-68
New Senior Secondary Mastering Biology (Second Edition)
Question Bank
Chapter 21
Essays
[10144533]
 Explain how the structure of leaves is adapted to obtain raw materials and energy
for photosynthesis.
(11 marks)
-- answer -Adaptation for obtaining light:
Leaf blade is broad and flat to provide a large surface area for absorbing sunlight. /
Leaf blade is thin to allow light to reach the photosynthetic cells easily. /
Palisade mesophyll consists of tightly packed cells which contain many chloroplasts to
allow effective absorption of sunlight. /
Palisade mesophyll is located on the upper side of the leaf to allow effective absorption
of sunlight.
(any 3)
1m x 3
Adaptation for obtaining carbon dioxide:
Spongy mesophyll consists of loosely packed cells with many air spaces to allow carbon
dioxide to diffuse freely inside the leaf.
1m
Upper and lower epidermis contains numerous stomata to allow gases to diffuse into the
leaf.
1m
Adaptation for obtaining water:
Upper and lower epidermis is covered by waxy cuticle to keep water inside the leaf for
photosynthesis.
1m
Each stoma is surrounded by a pair of guard cells to regulate the passage of water
vapour into and out of the leaf.
1m
Midrib and veins contain xylem which allows efficient transport of water into the leaf.
1m
Communication
3m
---------------------------------------------------
© Oxford University Press
21-69