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Hwa Chong Institution
Sec 1 Lower Sec Science
Photosynthesis 02
Name: ______________________ (
)
Class: ______
Science
INtegrated
Programme
Date: _______
What is photosynthesis?
Photosynthesis is the process by which plants use ____________________, ________ and ________
trapped by ___________________ to make food in the form of ______________, with ___________
being given off during the process.
(Greek: photos = light; synthesis = putting together)
General word equation for photosynthesis:
___________________ + _________
______________ + ____________
Photosynthesis takes place in ___________________. They are found in the __________________
of a plant cell.
Why are plants green?
Chloroplasts have ___________ pigments called _______________ to trap sunlight. Chlorophyll
absorbs mostly red & blue light for photosynthesis, and reflects green light.
Photosynthesis – A Short Summary
During photosynthesis, __________ energy is absorbed by ________________ and transformed into
____________ energy. The chemical energy is used in the synthesis of ______________ from
carbon dioxide and water. ____________ is given off during the process.
Glucose
Glucose is a simple sugar used to provide food for the plant and to make proteins, fats, and cellulose
cell walls. Excess glucose produced is stored in the form of ____________ in leaves and storage
organs such as storage stems.
Oxygen
Oxygen is used by the plant cells for aerobic respiration. Excess oxygen is removed by the plant to
the surroundings.
How do plants take in carbon dioxide and remove oxygen?
Carbon dioxide diffuses into the plant through the ______________. Excess oxygen leaves the plant
through the stomata by diffusion.
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How do we know photosynthesis has occurred?
If photosynthesis has taken place, glucose will be formed. Excess glucose produced is stored in the
form of starch. The presence of starch in leaves shows that photosynthesis has taken place. The
____________________ will be used to test for starch.
Iodine Test
Iodine solution is _____________________ in colour. Iodine solution turns _______________ in the
presence of starch.
Procedure:
1.
Put plant in darkness for a few days
2.
Expose plant to sunlight for a few hours
3.
Remove a green leaf from the plant
4.
Put leaf in boiling water for a few minutes
5.
Put boiled leaf in boiling tube containing ethanol. Place boiling tube in hot water bath.
6.
Remove leaf from boiling tube. Place leaf in hot water to soften it
7.
Remove leaf from water
8.
Add a few drops of iodine solution to the leaf.
What is the purpose of putting the leaf in boiling water?
__________________________________________________________________________________
What is the purpose of ethanol?
__________________________________________________________________________________
What is the colour of the ethanol
(a) before the leaf is placed inside
(b) 10 minutes after the leaf is placed inside
__________________________________________________________________________________
What happened to the leaf after 10 minutes in ethanol?
__________________________________________________________________________________
Is carbon dioxide necessary for starch formation?
Procedure:
1.
Grow a potted plant in a bell-jar in the absence of carbon dioxide.
2.
Absorb carbon dioxide from the air in the jar using sodium or potassium hydroxide solution.
3.
Do a comparison with a plant grown in normal air containing carbon dioxide.
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Is chlorophyll necessary for starch formation?
For this investigation, _________________ leaves are required. In a variegated leaf, some parts are
green and some parts are without chlorophyll.
Procedure:
1.
Destarch a plant with variegated leaves by placing it in the dark for 2 days.
2.
Expose plant to strong sunlight for a few hours.
3.
Remove a variegated leaf.
4.
Make a drawing of the leaf to show the distribution of chlorophyll.
5.
Test the leaf for starch.
Conditions essential for photosynthesis
1.
2.
3.
4.
5.
Importance of photosynthesis
1.
Photosynthesis makes chemical energy available to animals.
Plants provide organisms with food and energy to live ______________ or ________________.
Plants are the ______________________________ because they produce their own food.
Thus, plants are called _______________.
Animals are called ________________.
2.
Photosynthesis removes carbon dioxide and provides oxygen.
Photosynthesis removes carbon dioxide from the air.
Oxygen produced by plants is used by living organisms in ___________________.
References:
1.
G.C.E. ‘O’ Level Biology Matters (Marshall Cavendish) by Lam Peng Kwan & Eric Y K Lam
(2008) Pg. 112 – 127.
2.
INSCIENCE Volume 2 (Star Publishing) by Ho Peck Leng (2008) Pg. 76 – 81.
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