Photosynthesis: End of topic exercises
Section A
Question 1
1.1
Various options are provided as possible answers to the following questions.
Choose the correct answer and write only the letter (A – D) next to the
question number (1.1.1 – 1.1.5) on your answer sheet, for example 1.1.6 D
1.1.1
Plants use oxygen…
A continuously.
B during the day only.
C during the night only.
D during photosynthesis only
1.1.2
Test tubes A and B below were placed in bright light.
pondweed
snail
water
Which of the following is correct regarding the test tubes?
A The amount of CO2 in test tube A will decrease.
B The amount of CO2 in test tube B will increase.
C The amount of O2 in test tube B will increase.
D The amount of O2 in test tube A will increase.
1.1.3
What are the products of the light reactions of photosynthesis that
are used in the light independent phase?
A CO2 and glucose
B H2O and O2
C ATP
D ADP
126
1.1.4
Which factor does not affect the rate of photosynthesis?
A
B
C
D
1.1.5
Oxygen concentration
Light intensity
Temperature
Carbon dioxide concentration
An experiment was set up to investigate whether oxygen is released
during photosynthesis. The result of the experiment is represented in
the following diagram.
Bell jar A
Bell jar B
After a short time,
the candle went out
The candle continues to
burn for a longer period
The following deductions were made before arriving at the
conclusion.
(i) Photosynthesis reduces the amount of CO2 inside bell jar B
(ii) The oxygen in bell jar A was completely used up and
combustion is not supported
(iii) Photosynthesis increases the amount of oxygen inside
bell jar B
(iv) The smoke produced inside bell jar A is due to the
extinguished burning candle.
Which one of the following sets of deductions is correct?
A (i) and (iv) only
B (i), (ii) and (iii) only
C (i), (iii) and (iv) only
D (iii) and (iv) only
(5 × 2) = (10)
127
1.2
Give the correct biological term for each of the following descriptions. Write
only the term next to the question number.
1.2.1
The green, light-trapping pigment in photosynthesis found in plant
leaves.
1.2.2
The splitting of water molecules into hydrogen and oxygen in the
presence of light.
1.2.3
Site of reactions of the light independent phase in the chloroplast.
1.2.4
The process in plants in which radiant energy is converted into
chemical energy.
1.2.5
Expected colour change of diluted iodine solution when the presence
of starch in a leaf is confirmed.
1.2.6
The general energy carrier in the cells of living organisms.
1.2.7
The form of carbohydrate in which energy is stored in most plants.
1.2.8
The organelle that absorbs radiant energy during photosynthesis.
1.2.9
The reagent used to test for the presence of starch.
1.2.10 The organic molecules that act as catalysts and control the
chemical reactions during photosynthesis.
(10 × 1) = (10)
1.3
Indicate whether each of the descriptions in Column I applies to A ONLY, B
ONLY, BOTH A AND B or NONE of the items in Column II. Write A only, B
only, both A and B or none next to the question number.
Column I
Column II
1.3.1 Molecule that stores energy
A: ATP
B: ADP
1.3.2 The organelle in which
photosynthesis takes place
A: mitochondria
B: chloroplast
1.3.3 Storage of chlorophyll
A: grana
B: lamella
1.3.4 Light dependent phase of
photosynthesis
A: matrix
B: stroma
1.3.5 Gas given off by green plants during
photosynthesis
A: O2
B: CO2
(5 × 2) = (10)
1.4
Scientists set up an apparatus to investigate the effect of temperature, light
intensity and carbon dioxide concentrations on plant growth. Using this
apparatus, they could control each factor.
128

The scientists set different temperatures, CO2 concentrations and light
intensity for four different groups of lettuce plants.

The average mass of lettuce plants serves as an indication of the rate
of photosynthesis.
Mean mass of lettuce plants after 21 days / grams
Study the results below and answer the questions that follow.
Results of the investigation
400
4% CO2, 25°C
4% CO2, 15°C
300
200
100
0,03% CO2, 25°C
0,03% CO2, 15°C
0
0
2
4
6
8
10
Light intensity / arbitrary units
1.4.1
What is the influence of light intensity on average mass of lettuce
plants?
(3)
1.4.2
Name two limiting factors that influence the rate of photosynthesis as
the light intensity increases?
(2)
1.4.3
How were the scientists able to increase the rate of
photosynthesis to the maximum level?
1.4.4
(3)
What would happen to the rate of photosynthesis if the
temperature is raised beyond 35°C? Give a reason for your
answer.
(2)
(10)
Section A: [40]
129
Section B
Question 2
2.1
When light shines on pondweed, Elodea Sp, bubbles of gas are released.
The rate at which bubbles of gas are produced can be used to measure the
rate of photosynthesis.
An investigation was carried out to study the effect of different colours of light
on the rate of photosynthesis in the pondweed.

The pondweed was exposed to one colour of light and left for 5
minutes before measurements were taken.

The time taken for the release of 20 bubbles was recorded.

The procedure was repeated using light of a different colour of
equal intensity.

The apparatus was set up as shown in the diagram below.
gas bubble
pondweed
The results are shown in the table below:
Colour of light
Time taken to release 20 bubbles (seconds)
Violet
80
Blue
40
Green
160
Yellow
140
Red
70
130
2.1.1
Which colour light is the best for photosynthesis?
2.1.2
State the:
2.1.3
a) independent variable
(1)
b) dependent variable
(1)
Calculate the average time taken for the release of 20 bubbles
for all colours. Show all working.
(3)
2.1.4
Express bubble production under violet, blue and green light as
a ratio.
(2)
2.1.5
Explain why the apparatus is left for 5 minutes under each colour
of light before taking measurements.
(2)
2.1.6
Without modifying the apparatus, how could the reliability of the
results be increased?
(2)
2.1.7
Using the results, explain how, when white light shines on the
plant, the leaves appear to be green.
2.1.8
2.2
(1)
Draw a bar graph of the results shown in the table.
Draw a labelled diagram of an organelle present in the leaves of plants
where photosynthesis takes place.
(2)
(6)
(20)
(5)
[25]
Question 3
An experiment was conducted to determine whether light is necessary for
photosynthesis. The procedure followed is given below:

A geranium potted plant was de-starched.

A cross-shaped light slit was cut out on an aluminium foil.

The aluminium foil stencil was then clipped onto one of the de-starched leaves
as shown in the diagram below.

The potted plant was exposed to bright sunlight for 4 to 5 hours.

After 5 hours the aluminium foil stencil was removed, and the leaf was tested
for starch.
131