Think about… 21.1Basic concepts of photosynthesis 21.2Requirements for photosynthesis
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Transcript of Think about… 21.1Basic concepts of photosynthesis 21.2Requirements for photosynthesis
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Think about…21.1 Basic concepts of photosynthesis21.2 Requirements for photosynthesis21.3 Site of photosynthesis 21.4 The process of photosynthesis21.5 The fate of photosynthetic products21.6 Factors affecting the rate of photosynthesisRecall ‘Think about…’Summary concept map
3controlled conditions.
A greenhouse (溫室 ) is a transparent building made for growing plants under
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The conditions promote photosynthesis to enhance plant growth.
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Crops like green peppers and tomatoes are not suitable to grow in Hong Kong.
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With greenhouses, farmers can grow them all year round.
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What conditions of a greenhousepromote photosynthesis1
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How do plants make food by photosynthesis2
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What is the significance ofphotosynthesis to the ecosystem3
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21.1 Basic concepts of photosynthesis
What is photosynthesis?
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What is photosynthesis?21.1 Basic concepts of photosynthesis
• an anabolic process
light energy chemical energyplants / algae
• the process by which organic substances are made from simple inorganic substances using light energy
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by-product
light absorbedby chlorophyll
What is photosynthesis?21.1 Basic concepts of photosynthesis
• overall equation:
CO2 water glucose O2
• occurs in chloroplasts
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What is photosynthesis?21.1 Basic concepts of photosynthesis
light
inorganic nutrientswater minerals
CO2
photosynthesis
• plants make their own food by photosynthesis
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What is photosynthesis?21.1 Basic concepts of photosynthesis
carbohydrates
lipids
proteins
organic nutrients
plant materials
photosynthesis
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What is the significance of
photosynthesis?
21.1 Basic concepts of photosynthesis
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21.1 Basic concepts of photosynthesis
1 Maintaining energy flow in ecosystem
green plants
consumers
photosynthesis
light energy
chemical energy in
chemical energy in
feeding
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21.1 Basic concepts of photosynthesis
2 Providing the basic food source• most organisms depend on plants
directly or indirectly for food
plant cowhuman
producer
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21.1 Basic concepts of photosynthesis
3 Maintaining oxygen and carbon dioxide balance
respiration burning of fuels
consume O2 release CO2
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21.1 Basic concepts of photosynthesis
3 Maintaining oxygen and carbon dioxide balance
• oxygen consumed is replaced by that released by plants during photosynthesis
• plants take in carbon dioxide for photosynthesis
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1 Photosynthesis is the process by which substances are made from simple inorganic substances using energy.
organic
light
21.1 Basic concepts of photosynthesis
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In plants, is made from carbon dioxide and water during photosynthesis. is released as a by-product.
glucose
Oxygen
1
21.1 Basic concepts of photosynthesis
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. there absorbs light energy to drive the photosynthetic reactions.
2 Photosynthesis occurs in the chloroplasts Chlorophyll
21.1 Basic concepts of photosynthesis
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the in the ecosystem.
3 During photosynthesis, light energy from the sun is captured by plants, and converted to energy stored in the organic substances produced. Photosynthesis maintains
chemical
energy flow
21.1 Basic concepts of photosynthesis
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It provides the basic for most organisms.
It maintains the balance of atmospheric and carbon dioxide.
food source
oxygen
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21.1 Basic concepts of photosynthesis
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21.2 Requirements for photosynthesis
How do we know if photosynthesis has
occurred?
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21.2 Requirements for photosynthesis
• test for the presence of starch to find out if photosynthesis has occurred
glucose formed in photosynthesis
starch
quick conversion
Has photosynthesis occurred?
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21.2 Requirements for photosynthesis
• starch formed before affects the results destarching (脫澱粉 )
Has photosynthesis occurred?
keep in darkness for 24 hrs
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21.2 Requirements for photosynthesis
1 Boil a leaf in water for a minute.
21.1Detection of starch produced from photosynthesis (the iodine test)
Video
leafboiling water
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21.2 Requirements for photosynthesis
2 Turn off the Bunsen burner. Transfer the leaf to a boiling tube half filled with absolute alcohol. Put the tube into a beaker of hot water.
21.1Detection of starch produced from photosynthesis (the iodine test)
alcoholhot water
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21.2 Requirements for photosynthesis
3 When the leaf has lost its green colour, i.e. decolourized, transfer it from the tube to hot water.
21.1Detection of starch produced from photosynthesis (the iodine test)
hot water
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21.2 Requirements for photosynthesis
4 Spread the leaf on a white tile. Add a few drops of iodine solution onto its surface. Observe any colour change in the leaf.
21.1Detection of starch produced from photosynthesis (the iodine test)
iodine
white tiledecolourized leaf
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21.2 Requirements for photosynthesis
21.1
Results and discussionThe iodine solution turns blue-black all over the leaf. This result indicates that starch is present in the whole leaf.
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21.2 Requirements for photosynthesis
• oxygen is a by-product of photosynthesis• test for oxygen using a glowing splint
Has photosynthesis occurred?
test tube
if oxygen is present,glowing splint relights
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21.2 Requirements for photosynthesis
1 Put a few Hydrilla plants in a beaker of dilute sodium hydrogencarbonate solution.
21.2Detection of oxygen produced from photosynthesis
Hydrilla
dilute sodium hydrogen- carbonate solution
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21.2 Requirements for photosynthesis
2 Put an inverted filter funnel on three stoppers to cover the plants. Put a test tube completely filled with dilute sodium hydrogencarbonate solution on top of the funnel.
filter funnel
stopper
21.2Detection of oxygen produced from photosynthesis
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21.2 Requirements for photosynthesis
3 Leave the set-up in bright light for at least one day.
21.2Detection of oxygen produced from photosynthesis
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21.2 Requirements for photosynthesis
4 Remove the test tube carefully so that the gas cannot escape. Put a glowing splint over the mouth of the test tube to test for oxygen.
21.2Detection of oxygen produced from photosynthesis
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21.2 Requirements for photosynthesis
Results and discussionThe glowing splint relights. This result shows that the gas released from Hydrilla is oxygen.
21.2
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21.2 Requirements for photosynthesis
• two set-ups in the investigation- experimental set-up: the factor
being tested is present
Requirements for photosynthesis
- control set-up: the factor is absent
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21.2 Requirements for photosynthesis
• impossible to remove chlorophyll from a leaf without killing it use plants with variegated
leaves (斑葉 )
Requirements for photosynthesis1 Chlorophyll
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21.2 Requirements for photosynthesis
Requirements for photosynthesis
Coleus
green part(chlorophyll present)
1 Chlorophyll
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21.2 Requirements for photosynthesis
Requirements for photosynthesis
Coleus
green part(chlorophyll present)
non-green part(chlorophyll absent)
1 Chlorophyll
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21.2 Requirements for photosynthesis
1 Destarch a variegated plant by putting it the dark for at least 24 hours. Pick a leaf and test it for starch.
21.3Investigation of the need for chlorophyll in photosynthesis
Video
variegated leaf
dark environment
Simulation
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21.2 Requirements for photosynthesis
2 Expose the whole plant to bright light for about 5 hours.
3 Pick a leaf. Draw a sketch of it to show the colour pattern.
4 Test the leaf for starch. Draw another sketch of it to show the result of the iodine test.
21.3Investigation of the need for chlorophyll in photosynthesis
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21.2 Requirements for photosynthesis
Results and discussionStarch is present only in the green parts which contains chlorophyll. There is no or little starch in the non-green parts where chlorophyll is absent. These results show that chlorophyll is required for photosynthesis. In this practical, the non-green parts of the leaf serve as the control.
21.3
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21.2 Requirements for photosynthesis
• put a leaf of a destarched plant in a condition without carbon dioxide
• put another leaf in normal atmosphere
Requirements for photosynthesis2 Carbon dioxide
• use potassium hydroxide to remove carbon dioxide
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21.2 Requirements for photosynthesis
1 Destarch a plant by putting it in the dark for at least 24 hours. Pick a leaf and test it for starch.
21.4Investigation of the need for carbon dioxide in photosynthesis
Simulation
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21.2 Requirements for photosynthesis
2 Set up the apparatus as shown.conical
flask
split cork or cotton wool
potassium hydroxide pellet
potted plant
leaf A
leaf B
21.4Investigation of the need for carbon dioxide in photosynthesis
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21.2 Requirements for photosynthesis
3 Expose the whole plant to bright light for about 5 hours.
4 Test leaves A and B for starch.
21.4Investigation of the need for carbon dioxide in photosynthesis
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21.2 Requirements for photosynthesis
Results and discussionStarch is present in leaf A but absent in leaf B. As leaf B is exposed to air without carbon dioxide, the results show that carbon dioxide is required for photosynthesis. In this practical, leaf B serves as the control.
21.4
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21.2 Requirements for photosynthesis
• needed in many other reactions in plants
Requirements for photosynthesis3 Water
difficult to do the investigation
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21.2 Requirements for photosynthesis
• prevented from reaching part of a leaf by masking it with black paper
Requirements for photosynthesis4 Light
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21.2 Requirements for photosynthesis
Connie’s plant turned yellow. Her brother told her to pull back the curtains.
21.5Design an investigation of the need for light in photosynthesis
Simulation
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21.2 Requirements for photosynthesis
After a week, the plant turned green again and grew healthily.
21.5Design an investigation of the need for light in photosynthesis
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21.2 Requirements for photosynthesis
Connie wondered if light is needed in photosynthesis. Suppose you were Connie, design and perform an investigation to find out the answer.
21.5Design an investigation of the need for light in photosynthesis
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1 is the removal of starch from the leaves of a plant by putting it in the dark for a period of time. This is to make sure that the starch detected at the end of the experiment was made the experiment.
Destarching
21.2 Requirements for photosynthesis
during
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2 Chlorophyll, , water and are required for photosynthesis to occur.
carbon dioxidelight
21.2 Requirements for photosynthesis
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21.3 Site of photosynthesis• all green parts of a plant contain
chloroplasts can carry out photosynthesis
• leaves contain the most chloroplasts leaves are the main site of
photosynthesis• both leaves and chloroplasts have
structural adaptations
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leaf blade
21.3 Site of photosynthesis
Adaptive features of a leaf
- broad and flat
provides a large surface area for absorbing sunlight
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leaf blade
21.3 Site of photosynthesis
Adaptive features of a leaf
- thin gases and light can reach
the photosynthetic cells easily
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21.3 Site of photosynthesis
Adaptive features of a leaf
network of veins
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21.3 Site of photosynthesis
Adaptive features of a leafmidrib - contains a vascular bundle
made up of xylem and phloem
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21.3 Site of photosynthesis
Adaptive features of a leafmidrib - branches into a network
of veins
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21.3 Site of photosynthesis
Adaptive features of a leaf provides efficient transport
of materials: water into and food away from the leaf
midrib
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21.3 Site of photosynthesis
Adaptive features of a leafmidrib supports and maintains
the shape of the leaf
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21.3 Site of photosynthesis
Adaptive features of a leaf
upper epidermis
lower epidermis
- covered by a thin layer of waxy cuticle
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21.3 Site of photosynthesis
Adaptive features of a leaf reduces water loss from the
leaf, so that water is kept inside for photosynthesis and keeping the cells turgid
upper epidermis
lower epidermis
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21.3 Site of photosynthesis
Adaptive features of a leaf- contains numerous stomata,
each surrounded by a pair of guard cells
upper epidermis
lower epidermis
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21.3 Site of photosynthesis
Adaptive features of a leaf guard cells open the stoma
when the conditions are favourable for photosynthesis
upper epidermis
lower epidermis
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21.3 Site of photosynthesis
Adaptive features of a leaf guard cells close the stoma
when the conditions are less favourable
upper epidermis
lower epidermis
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21.3 Site of photosynthesis
Adaptive features of a leaf this allows the passage of
gases and water vapour into and out of the leaf
upper epidermis
lower epidermis
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palisade mesophyll
21.3 Site of photosynthesis
Adaptive features of a leaf
- consists of tightly packed cells that contain many chloroplasts
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21.3 Site of photosynthesis
Adaptive features of a leaf
- located on the upper side of the leaf
palisade mesophyll
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21.3 Site of photosynthesis
Adaptive features of a leaf
allows effective absorption of sunlight
palisade mesophyll
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spongy mesophyll
21.3 Site of photosynthesis
Adaptive features of a leaf
- consists of loosely packed cells with many air spaces
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21.3 Site of photosynthesis
Adaptive features of a leaf
allows gases to diffuse freely inside the leaf
spongy mesophyll
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Adaptive features of a leaf to photosynthesis:
• provides a large surface area for absorbing
1a Leaf blade is broad and . flat
21.3 Site of photosynthesis
sunlight
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and light can reach the photosynthetic cells easily
1b Leaf blade is thin.
gases
21.3 Site of photosynthesis
Adaptive features of a leaf to photosynthesis:
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• allows effective absorption of sunlight
2a Palisade mesophyll consists of tightly packed cells that contain many chloroplasts
21.3 Site of photosynthesis
.
Adaptive features of a leaf to photosynthesis:
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• allows effective absorption of sunlight
2b Palisade mesophyll is located on the upper
21.3 Site of photosynthesis
side of the leaf.
Adaptive features of a leaf to photosynthesis:
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• allows to diffuse freely inside the leaf
3 Spongy mesophyll consists of loosely packed cells withair spaces
21.3 Site of photosynthesis
gases.
Adaptive features of a leaf to photosynthesis:
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• reduces water loss from the leaf
4a Upper and lower epidermis is covered by a thin layer of waxy cuticle
21.3 Site of photosynthesis
.
Adaptive features of a leaf to photosynthesis:
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• so that water is kept inside for photosynthesis and keeping the cells
21.3 Site of photosynthesis
turgid
Adaptive features of a leaf to photosynthesis:
4a Upper and lower epidermis is covered by a thin layer of waxy cuticle .
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4b Upper and lower epidermis contains numerous , each surrounded by a pair of .
stomata
21.3 Site of photosynthesis
• allow the passage of gases and water vapour into and out of the leaf
guard cells
Adaptive features of a leaf to photosynthesis:
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5 contains a vascular bundle made up of xylem and phloem. It also branches into a network of .
Midrib
21.3 Site of photosynthesis
• provides efficient transport of materials
veins
Adaptive features of a leaf to photosynthesis:
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21.3 Site of photosynthesis
• supports and maintains the
Adaptive features of a leaf to photosynthesis:5 contains a vascular
bundle made up of xylem and phloem. It also branches into a network of .
Midrib
veins
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21.3 Site of photosynthesis
1 Examine the external structures of a dicotyledonous leaf and draw a labelled diagram.
21.6Examination of the structure of leaves
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2 Examine the photomicrograph or the prepared slide of the transverse section of a dicotyledonous leaf under a microscope.
21.6Examination of the structure of leaves
21.3 Site of photosynthesis
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21.6Examination of the structure of leaves3 Identify the internal structures of the leaf
and draw a high power diagram.
21.3 Site of photosynthesis
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Adaptive features of a chloroplast
21.3 Site of photosynthesis
• bound by a double membrane• filled with a jelly-like fluid called
stroma (基質 )
outer membraneinner membrane
stroma
3D model
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Adaptive features of a chloroplast
21.3 Site of photosynthesis
• stroma contains enzymes• stroma holds temporary stores of
photosynthetic products
starch grains
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Adaptive features of a chloroplast
21.3 Site of photosynthesis
• chlorophyll is located in the thylakoid membrane
thylakoidgranum (基粒 )
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Adaptive features of a chloroplast
21.3 Site of photosynthesis
• about 50 grana, each consisting of about 50 thylakoids provide a large area to pack
more chlorphyll
thylakoidgranum (基粒 )
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Adaptive features of a chloroplast
21.3 Site of photosynthesis
• grana are interconnected
allows efficient transport of photosynthetic products
thylakoidgranum (基粒 )
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21.3 Site of photosynthesis
1 Examine the photomicrograph or live cell image of a chloroplast.
21.7Examination of the structure of chloroplasts
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21.3 Site of photosynthesis
21.7Examination of the structure of chloroplasts2 Identify various structures of the chloroplast
and draw a high power diagram.
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• holds which are temporary stores of photosynthetic products
• contains that catalyse photosynthetic reactions
1 Stroma is a jelly-like fluid. enzymes
21.3 Site of photosynthesis
starch grains
Adaptive features of a chloroplast to photosynthesis:
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• provide a large to pack chlorophyll
2a Thylakoids are membranous sacs with space inside. They are large in numbers and arranged in stacks called .grana
21.3 Site of photosynthesis
surface area
Adaptive features of a chloroplast to photosynthesis:
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2b Grana are interconnected by the extensions from thylakoids.• allows efficient of
photosynthetic products within the chloroplast
transport
21.3 Site of photosynthesis
Adaptive features of a chloroplast to photosynthesis:
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21.4 The process of photosynthesis
Let’s recall the overall equation
of photosynthesis.
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21.4 The process of photosynthesis
• includes two main stages:
carbon fixation (碳固定 )
photochemical reactions (光化學反應 )
light absorbedby chlorophyll
CO2 water glucose O2
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• occur in thylakoids• require light• also called light reactions
21.4 The process of photosynthesis
Photochemical reactions
• involve three main processes:
generation of ATP
light absorption
photolysis of water
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• chlorophyll absorbs light energy• some electrons in chlorophyll are raised
to higher levels
21.4 The process of photosynthesis
Photochemical reactions1 Light absorption
excited electrons
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• excited electrons pass along the electron transport chain (電子傳遞鏈 )
21.4 The process of photosynthesis
Photochemical reactions1 Light absorption
electron carriers of decreasing energy levels
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• excited electrons pass along the electron transport chain (電子傳遞鏈 )
21.4 The process of photosynthesis
Photochemical reactions1 Light absorption
e
energyenergy
energy
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• excited electrons pass along the electron transport chain (電子傳遞鏈 )
21.4 The process of photosynthesis
Photochemical reactions1 Light absorption
energy is released gradually
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energy released by electrons
21.4 The process of photosynthesis
Photochemical reactions2 Generation of ATP
adenosine
ADP (腺苷二磷酸 )
P P Pphosphate
group
adenosineP P P
ATP (腺苷三磷酸 )
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• photophosphorylation (光磷酸化 )
21.4 The process of photosynthesis
Photochemical reactions
light energy
chemical energy
absorbed by chlorophyll
stored in ATP
2 Generation of ATP
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21.4 The process of photosynthesis
Photochemical reactions3 Photolysis of water
H2Ooxygen
hydrogen
energy released by electrons
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reducing agent in carbon fixation
• oxygen is released as a gas to the atmosphere
21.4 The process of photosynthesis
Photochemical reactions3 Photolysis of water
• hydrogen is accepted by NADPNADP + H NADPH
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21.4 The process of photosynthesis
Photochemical reactionsSummary
ATP
oxygen
NADPH
by-product
used to drive carbon fixation
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• occurs in stroma• does not require light• also called dark reactions
and Calvin cycle (卡爾文循環 )
21.4 The process of photosynthesis
Carbon fixation
discover: Melvin Calvin
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• three steps:
21.4 The process of photosynthesis
Carbon fixation
1 Carbon dioxide fixation & formation of 3-C compound
CO2
5-C compound
3-C compound2 x
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• three steps:
21.4 The process of photosynthesis
Carbon fixation
2 Reduction of 3-C compound and formation of glucose
ATP
triose phosphate (3-C)
3-C compound
NADPHADP + P
NADP
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• three steps:
21.4 The process of photosynthesis
Carbon fixation
2 Reduction of 3-C compound and formation of glucose
2 x triose phosphate (3-C)
glucose (6-C)
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• three steps:
21.4 The process of photosynthesis
Carbon fixation
3 Regeneration of carbon dioxide acceptor
triose phosphate (3-C)
5-C compound
ATPADP + P
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21.4 The process of photosynthesis
light absorbed by chlorophyll 6 CO2 6 H2O C6H12O6 O2
Photochemical reactions
chloroplastthylakoid
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NADPH
21.4 The process of photosynthesis
light
H2O
ATP
O2
light absorbed by chlorophyll 6 CO2 6 H2O C6H12O6 O2
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21.4 The process of photosynthesis
Calvin cycle
stroma
NADPHlight
H2O
ATP
O2
light absorbed by chlorophyll 6 CO2 6 H2O C6H12O6 O2
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21.4 The process of photosynthesis
CO2
glucose
ADP + P
NADPHlight
H2O
ATP
O2
NADP
light absorbed by chlorophyll 6 CO2 6 H2O C6H12O6 O2
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releasing gradually.
Chlorophyll absorbs and some electrons in the chlorophyll are excited. These excited electrons then pass along the ,
light energy
electron transport chain
21.4 The process of photosynthesis
1 Photochemical reactions:
energy
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Energy released by the electrons is used to form from a phosphate group and ADP. Light energy is converted into
ATP
chemicalenergy in ATP.
21.4 The process of photosynthesis
1 Photochemical reactions:
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Water molecules are split into hydrogen and oxygen using energy released by the electrons ( of water). Oxygen is released as a gas. Hydrogen is accepted by NADP to form .
photolysis
NADPH
21.4 The process of photosynthesis
1 Photochemical reactions:
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is accepted by a 5-C compound to form two molecules of a 3-C compound.
Under the action of enzymes, carbon dioxide
21.4 The process of photosynthesis
2 Calvin cycle:
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. It is then used to synthesize .
Using energy from ATP and hydrogen from NADPH, the 3-C compound is reduced to triosephosphate
glucose
21.4 The process of photosynthesis
2 Calvin cycle:
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Some triose phosphate molecules are used to regenerate the original 5-C carbon dioxide , so that the Calvin cycle can repeat. The regeneration uses energy from .
acceptor
21.4 The process of photosynthesis
ATP
2 Calvin cycle:
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produced from photochemical reactions to operate.
3 The Calvin cycle requires andNADPH
and formed in the Calvin cycle are used in photochemical reactions.
ADP
21.4 The process of photosynthesis
ATP
NADP
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21.5 The fate of photosynthetic products
• primary product: triose phosphate • triose phosphate and other intermediates
can be converted to other biomolecules
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21.5 The fate of photosynthetic products
1 Carbohydratestriose phosphate
glucose - main energy source
starch - for storage
sucrose - transported by phloem
cellulose - major component of cell walls
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21.5 The fate of photosynthetic products
1 Carbohydrates• stored in different parts of plants as
energy reserve• some plants store starch
grains, e.g. potato tubers• some plants convert
starch into lipids, e.g. corn
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21.5 The fate of photosynthetic products
2 Lipids
• form cell membranes
intermediates of photosynthesis
glycerol fatty acids
lipids
• as food reserve
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21.5 The fate of photosynthetic products
3 Proteins
• for growth and repair
intermediates of photosynthesis
inorganic ions amino acids
• components of cell membranes
• for synthesis of enzymes
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1 Triose phosphate is converted to carbohydrates like glucose, sucrose, and .starch
21.5 The fate of photosynthetic products
cellulose
Fate of photosynthetic products:
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then converted to which is transported to other parts of the plant.
In dicotyledonous plants, glucose is soon converted to . It is
21.5 The fate of photosynthetic products
sucrose
Fate of photosynthetic products:2
starch
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and fatty acids which form , and which
form proteins.
The intermediates of photosynthesis are converted to glycerol
21.5 The fate of photosynthetic products
lipids amino acids
3Fate of photosynthetic products:
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21.6 Factors affecting the rate of photosynthesis
Let’s study the effects of light intensity and carbon dioxide concentration on the rate of
photosynthesis.
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21.6 Factors affecting the rate of photosynthesis
Light intensity• use Hydrilla to study the effect
• the rate of oxygen bubbles being given off indicates the rate of photosynthesis
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1 Set up the apparatus as shown.
21.8Investigation of the effects of light intensity on the rate of photosynthesis
Simulation
rubber tubingclippipette
dilute sodium hydrogencarbonate solution
thermometer
Hydrilla
21.6 Factors affecting the rate of photosynthesis
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1 Check the thermometer to ensure a constant temperature. Turn on the bench lamp at a distance of 0.1 m from the plant. Allow the plant to equilibrate for 5 minutes.
21.8Investigation of the effects of light intensity on the rate of photosynthesis
21.6 Factors affecting the rate of photosynthesis
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2 Suck up the solution from the boiling tube. Close the clip completely and record the starting position of the meniscus in the pipette.
21.8Investigation of the effects of light intensity on the rate of photosynthesis
3 After 5 minutes, record the final position of the meniscus in the pipette. Calculate the rate of photosynthesis. Record two more readings.
21.6 Factors affecting the rate of photosynthesis
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4 Repeat steps 1 to 3 with the bench lamp placed at a distance of 0.2 m, 0.3 m, 0.4 m and 0.5 m from the plant.
21.8Investigation of the effects of light intensity on the rate of photosynthesis
21.6 Factors affecting the rate of photosynthesis
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Results and discussionAt low to moderate level of light intensity, the rate of photosynthesis increases proportionally with increasing light intensity. This is because more energy is provided to the plant to carry out photosynthesis.
21.821.6 Factors affecting the rate of photosynthesis
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Results and discussionWhen light intensity has reached a certain level, the rate of photosynthesis does not increase with further increase in light intensity. This is because other factors such as carbon dioxide concentration become limiting.
21.821.6 Factors affecting the rate of photosynthesis
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21.6 Factors affecting the rate of photosynthesis
Light intensity
• the rate increases rapidly with light intensity as more energy is supplied
rate
of
phot
osyn
thes
is
light intensity
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21.6 Factors affecting the rate of photosynthesis
Light intensity
• the increase levels off when light intensity reaches a saturation point
rate
of
phot
osyn
thes
is
light intensity
saturation point (飽和點 )
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21.6 Factors affecting the rate of photosynthesis
Light intensity
• the rate is now limited by other factors such as temperature
rate
of
phot
osyn
thes
is
light intensity
saturation point (飽和點 )
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21.6 Factors affecting the rate of photosynthesis
Light intensityra
te o
f ph
otos
ynth
esis
light intensity
saturation point (飽和點 )
optimum light intensity
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• the rate increases with CO2 concentration as more substrates are supplied to Calvin cycle
21.6 Factors affecting the rate of photosynthesis
Carbon dioxide concentrationra
te o
f ph
otos
ynth
esis
light intensity
low CO2 concentration
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• if the CO2 concentration is increased, the rate levels off at a higher rate
21.6 Factors affecting the rate of photosynthesis
Carbon dioxide concentrationra
te o
f ph
otos
ynth
esis
light intensity
low CO2 concentration
high CO2 concentration
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Design an investigation of the effect of carbon dioxide concentration on the rate of photosynthesisPractical 21.4 shows that carbon dioxide is required for photosynthesis. Revise Practical 21.8 and try to design an experiment to investigate the effect of carbon dioxide concentration on the rate of photosynthesis.
21.921.6 Factors affecting the rate of photosynthesis
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21.6 Factors affecting the rate of photosynthesis
Regulating the rate of photosynthesis• by monitoring the light intensity and
CO2 concentration in greenhouses increase productivity (生產力 ) improve quality
of crops
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up to a certain point and then becomes because the rate is limited by other factors.
1 The rate of photosynthesis increases with light intensity. As the factor increases, the rateincreases
constant
21.6 Factors affecting the rate of photosynthesis
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with carbon dioxide concentration. It will finally level off because of other .
2 The rate of photosynthesisincreases
21.6 Factors affecting the rate of photosynthesis
limiting factors
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What conditions of a greenhouse 1promote photosynthesis?The increased light intensity, carbon dioxide concentration and temperature promote photosynthesis.
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How do plants make food by2photosynthesis?During photosynthesis, light energy captured by chlorophyll is used to drive the reduction of carbon dioxide to form carbohydrates.
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What is the significance of 3photosynthesis to the ecosystem?Photosynthesis maintains the energy flow in the ecosystem and provides the basic food source for most organisms. It also maintains the balance of atmospheric oxygen and carbon dioxide.
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occurs in two stages
light energy
Photosynthesis
captures and converts
photochemical reactions
Calvin cycle
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converted to
stored in
absorbed by
present in
mostly in
light energy
chlorophyll chemical energy
chloroplasts organic compounds
leaves
159
providingmaintainingimportant in
Photosynthesis
energy flow in ecosystem
basic food source
balance of atmospheric oxygen and carbon dioxide
maintaining
160
produce
produces
involve
photochemical reactions
photolysis of water
oxygen NADPH
ATP
161
Calvin cycle
involves
reduction of carbon dioxide
NADPH
ATP used in
glucoseproduces