Transcript expphotosynthesis1

Photosynthesis
光合作用
香港道教聯合會青松中學
吳友強
2016/7/24
Quick Revision :
Where does photosynthesis occur？
Leaf 葉片
X-section
橫切面 :
Palisade
mesophyll
柵狀葉肉
Chloroplast under electron microscope
Chloroplast
葉綠體
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電子顯微鏡下的葉綠體
Warm-up Questions
The following microphotograph is a
transverse section of a
A. stem.
B. leaf.
C. root.
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Sorry, you’ve got the wrong answer!!!
Can you find cortex (皮層), which is
very obvious in a cross-section of a
stem ?
Try again...
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Sorry, you’ve got the wrong answer!!!
Are the vascular bundles(維管束)
concentrated in the centre
of the section ?
Try again...
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Congratulations!!!
You’ve got the
correct answer!!!
Go to next
question...
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Warm-up Questions
Here is a transverse section of a leaf. It is a
leaf of
A. monocotyledonous xerophyte
B. dicotyledonous hydrophyte
C. dicotyledonous mesophyte
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Sorry, you’ve got the wrong answer!!!
Xerophyte is a kind of plants
adapted in desert habitat.
Try again...
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Sorry, you’ve got the wrong answer!!!
Hydrophyte is a kind of plants
adapted in aquatic habitat.
Try again...
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Congratulations!!!
You’ve got the
correct answer!!!
Bonus …….
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Bonus :
Give two reasons to support
your answer.
Hints ----???
???
???
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Definition of Photosynthesis
Photosynthesis is a process by which
green plants use sunlight trapped by
chlorophyll to produce organic
compounds (carbodyrate) from carbon
dioxide and water, oxygen is released as
by-product.
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Summary of Photosynthesis
Carbon
dioxide
二氧化碳
Sunlight
陽光
Water
水
Chlorophyll
葉綠素
Oxygen
氧
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Glucose
葡萄糖
Experiments :
light
6CO2 ＋ 6H2O
C6H12O6 + 6O2
chlorophyll
1.To show that starch is produced during
Photosynthesis.
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Four steps :
1.Boil the leaf in water, why ?
2.Boil the leaf in alcohol, why ?
3.Wash the leaf in warm water, why ?
4.Add iodine solution to the leaf,
what is the expected result ?
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Experiments :
light
6CO2 ＋ 6H2O
C6H12O6 + 6O2
chlorophyll
Aim :
To show that light is necessary for Photosynthesis.
Control :
Do we need a Control for this experiment ?
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Experiments :
light
6CO2 ＋ 6H2O
C6H12O6 + 6O2
chlorophyll
Aim :
To show that chlorophyll is necessary for photosynthes
Control :
Do we need a Control for this experiment ?
Any Assumption ?
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Experiments :
light
6CO2 ＋ 6H2O
C6H12O6 + 6O2
chlorophyll
Aim :
To show that carbon dioxide is necessary for
photosynthesis.
Any Criticism on the set-up ?
(Think about Variables.)
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light
6CO2 ＋ 6H2O
C6H12O6 + 6O2
chlorophyll
Is it better ?
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Experiments :
light
6CO2 ＋ 6H2O
C6H12O6 + 6O2
chlorophyll
Aim :
To show that oxygen is produced during
photosynthesis.
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Logics
In an experiment, think about :
Aim and objective
Control experiment
Dependent variables
Independent variables
Assumptions
Limitations
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Limitations of the summary
equation :
light
6CO2 ＋ 6H2O
C6H12O6 + 6O2
chlorophyll
1.Photosynthesis is a two phase process,
which cannot be shown in the equation.
2.Source of oxygen cannot be shown.
3.Glucose is not the first product of
photosynthesis.
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Photosynthesis involves two stages :
Light reaction
• light is necessary
• light split water into hydrogen and oxygen
Dark reaction
• light is not necessary
• hydrogen is used to reduce carbon dioxide
to carbodyrate
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Light reaction
Light
陽光
Water
水
Chlorophyll
葉綠素
Oxygen
氧
Released from
the plant
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Hydrogen氫
（原子）
Dark reaction
Dark reaction
Hydrogen氫
（原子）
Carbohydrate
碳水化合物
Carbon
dioxide
二氧化碳
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