What is photosynthesis

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SQ_Photosynthesis.doc/CE Biology/ymt/aoghss
1.
What is photosynthesis?
2
2.
What are the raw materials for photosynthesis?
2
3.
State the energy change that occurs during photosynthesis.
1
4.
What is the source of oxygen released during photosynthesis
1
5.
State the role of chlorophyll in photosynthesis.
2
6.
Name the two sets of reactions of photosynthesis and state two differences between
them.
4
7.
Sketch a graph to show the effect of a change in light intensity on the rate of
photosynthesis.
2
8.
Sketch a graph to show the effect of a change in carbon dioxide on the rate of
2
photosynthesis.
9.
Sketch a graph to show the effect of a change in temperature on the rate of
photosynthesis.
2
10.
Name two coloured lights are most effective for photosynthesis.
2
11.
State the functions of the following parts of the leaf (one each):
cuticle, palisade mesophyll, spongy mesophyll, stomata, guard cells
1
12.
State and explain how the shape of a leaf is adapted to photosynthesis
2
13.
State the explain the steps used to test for the presence of starch in a green leaf.
8
14.
Explain why it is necessary to destarch the leaf before we carry out experiments to
test for the necessity of light for photosynthesis.
1
15.
In an experiment to test for the necessity of light for photosynthesis, which set-up is 1
the control?
16.
In an experiment to test for the necessity of light for photosynthesis, which set-up is
the control?
1
17.
(a) Draw a labelled diagram to show the set up of an experiment to show that
oxygen is given out during photosynthesis.
4
(b) Explain why the water weed is used instead of a land plant.
1
(c) Explain why the water weed is immersed in sodium hydrogen carbonate
solution instead of water.
1
(d) How would you set up a control for this experiment.
1
Explain the importance of photosynthesis to animals.
3
18.
SQ_Photosynthesis.doc/CE Biology/ymt/aoghss
Answers:
1.
Photosynthesis is the process in which green plants make glucose/food from water
1
and carbon dioxide in the presence of light.
1
2.
Raw materials for photosynthesis are: carbon dioxide and water
1, 1
3.
Light is changed to chemical energy
1
4.
Oxygen released in photosynthesis comes from water.
1
5.
Chlorophyll absorbs light energy
1
converting it into chemical energy / for photolysis of water / driving carbon fixation 1
6.
The two sets of reactions of photosynthesis are: light reaction and dark reaction
Differences between light reaction and dark reaction:
 Light reaction occurs in the presence of light but dark reaction occurs in both

light and dark conditions
In light reaction, oxygen is given out. In dark reaction glucose is produced
1, 1
1
1
7.
See notes (all or none)
2
8.
See notes (all or none)
2
9.
See notes (all or none)
2
10.
Red and blue lights are most effective for photosynthesis
1, 1
11.
cuticle
To reduce water loss / forms a waterproof layer on leaf surface
protects the leaf from injuries
1
Palisade
mesophyll
To carry out photosynthesis
1
Spongy
mesophyll
To carry out photosynthesis / for gaseous exchange / for
transpiration
1
Stomata
For transpiration / forms a passage for gases to enter and leave
leaf
1
Guard cell
It controls the opening and closing of the stoma
1
12.
See notes:
 palisade mesophyll cell: more chloroplasts (1), elongated shape (1)
 spongy mesophyll cell: less chloroplasts (2), rounded shape (1)

13.
*Labels: cell wall, chloroplasts, nucleus, vacuole, cell membrane (any 4, ½ each)
The leaf is flattened in shape
1
To provide a large surface area for trapping solar energy / diffusion of gases
1
14.
Place the leaf in boiling water to kill the leaf cells
Place the leaf in boiling alcohol to decolourize the leaf
Place the leaf in warm water to soften the leaf / wash away the alcohol
Add iodine solution to the leaf to test for starch
1, 1
1, 1
1, 1
1, 1
15.
This is to ensure that the leaf cells contain no starch before the experiment / starch
tested later is formed during the experiment
1
16.
The plant/leaf which receives no light is the control
1
SQ_Photosynthesis.doc/CE Biology/ymt/aoghss
17.
(a)
See notes


(b)
Oxygen released can be easily detected/observed
1
(c)
Sodium hydrogen carbonate solution provides carbon dioxide/ hydrogen
carbonate ions for photosynthesis
1
The control set-up: same apparatus but covered with a black cloth
1
(d)
18.
correct design
2
Labels: water weed, sodium hydrogen carbonate solution, bubbles given
out / device to collect gas (any 2, l mark each)
1, 1
Oxygen produced in photosynthesis is used for respiration by animals
Food produced by photosynthesis is consumed by animals for growth and repair.
1, 1
1
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