2016
Chapter 10: Photosynthesis
From Topic 2.9
Essential idea: Photosynthesis uses the energy in sunlight to produce
the chemical energy needed for life.
Nature of science: Experimental design—controlling relevant variables
in photosynthesis experiments is essential (3.1).
Understandings:
• Photosynthesis is the production of carbon compounds in cells using light energy.
• Chlorophyll absorbs red and blue light most effectively and reflects green light more than other colours.
• Oxygen is produced in photosynthesis from the photolysis of water. • Energy is needed to produce carbohydrates and other carbon compounds from carbon dioxide.
• Temperature, light intensity and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis.
Applications and skills:
• Application: Changes to the Earth’s atmosphere, oceans and rock deposition due to photosynthesis.
• Skill: Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis.
• Skill: Separation of photosynthetic pigments by chromatograph (Practical 4).
• Skill: Design of experiments to investigate the effect of limiting factors on photosynthesis.
Guidance:
• Water free of dissolved carbon dioxide for photosynthesis experiments can be produced by boiling and cooling water.
• Students should know that visible light has wavelengths between 400 and 700 nanometres, but they are not expected to recall the wavelengths of specific colours of light.
• Paper chromatography can be used to separate photosynthetic pigments but thin layer chromatography gives better results.
From Topic 8.3
Essential idea: Light energy is converted into chemical energy. Nature of science: Developments in scientific research follow
improvements in apparatus—sources of 14C and autoradiography enabled Calvin to elucidate the pathways of carbon fixation (1.8).
Understandings:
•The structure of the chloroplast is adapted to its function in photosynthesis.
• Light-dependent reactions take place in the intermembrane space of the thylakoids.
• Reduced NADP and ATP are produced in the light-dependent reactions.
• Absorption of light by photosystems generates excited electrons. • Photolysis of water generates electrons for use in the
light-dependent reactions.
• Transfer of excited electrons occurs between carriers in thylakoid membranes.
• Excited electrons from Photosystem II are used to contribute to generate a proton gradient.
• ATP synthase in thylakoids generates ATP using the proton gradient. • Excited electrons from Photosystem I are used to reduce NADP. Light-independent reactions take place in the stroma.
• In the light-independent reactions a carboxylase catalyses the carboxylation of ribulose bisphosphate.
• Glycerate 3-phosphate is reduced to triose phosphate using reduced NADP and ATP.
• Triose phosphate is used to regenerate RuBP and produce carbohydrates.
Chapter 10: Photosynthesis
From Topic 8.3
Applications and skills:
• Application: Calvin’s experiment to elucidate the carboxylation of RuBP.
•Skill: Annotation of a diagram to indicate the adaptations of a chloroplast to its function.
Aim 6: Hill/s method demonstrating electron transfer in chloroplasts by observing DCPIP reduction, immobilization of a culture of an alga such
as Scenedesmus in alginate beads and measurement of the rate of photosynthesis by monitoring their effect on hydrogencarbonate indicator are all possible experiments.
Utilization:
• The Global Artificial Photosynthesis (GAP) project aims to create an artificial “leaf” within the next decade. An electronic version of the leaf that creates oxygen and hydrogen from water and sunlight has already been invented and will be developed for use in the next decade.
From Topic 9.1 Understandings:
• Transpiration is the inevitable consequence of gas exchange in the leaf.
Applications and skills:
Ecology Review
•
Plants, algae and other autotrophs are the producers in the
ecosystem.
•
Autotrophs synthesize organic molecules from
inorganic raw materials.
•
Heterotrophs acquire organic molecules from
Site of Photosynthesis
• Photosynthesis is the production of carbon compounds in cells using light energy.
Annotation of a diagram to indicate the adaptations of a chloroplast to its function
•The structure of the chloroplast is adapted to its function in photosynthesis.
•
Site of photosynthesis is in the
chloroplast.
•
Chloroplasts are found mainly in the
mesophyll of the leaf, in the palisade
Structure and Function of Chloroplast
• Light-dependent reactions take place in the intermembrane space of the thylakoids. • Transfer of excited electrons occurs between carriers in thylakoid membranes. Light-independent reactions take place in the stroma.
Guard Cells
•
Stomata: little openings in
the leaf controlled by guard
cells
- let’s in CO
2
but also let’s
out water
•
How do guard cells work?
Chlorophyll
• Chlorophyll absorbs red and blue light most effectively and reflects green light more than other colours. • Skill: Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis.
•
Chlorophyll: a green pigment in the chloroplast that absorbs
light
•
Two types of chlorophyll:
Overview of Photosynthesis
Photosynthesis uses the energy in sunlight to produce the chemical energy needed for life.• Photosynthesis is the production of carbon compounds in cells using light energy : Light energy is converted into chemical energy
•
Transforms solar energy into chemical
energy.
•
CO
2
and H
2
O into Glucose
•
CO
2
is carbon source and light is energy
Two Stages of Photosynthesis
• Temperature, light intensity and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis.
•
Light Dependent Reactions
(Light Reactions)
•
Products
•
Oxygen
•
NADPH
•
ATP
•
Light Independent
Reactions (Dark Reactions
or Calvin Cycle)
•
Products:
•
Glucose
Light Reactions (Non-Cyclic e- Flow)
• Light-dependent reactions take place in the intermembrane space of the thylakoids.
•
Light Reactions: the “photo” part of photosynthesis; requires
light to make it happen
- Similar to how the ETC of Cellular Respiration works
http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120072/bio13.swf::Photosynthetic%20Electron%20Transport%20and%20ATP%20Synthesis
Light Reactions (Non-Cyclic e- Flow)
• Light-dependent reactions take place in the intermembrane space of the thylakoids. • Reduced NADP and ATP are produced in the light-dependent reactions
. • Photolysis of water generates electrons for use in the light-dependent reactions.
•
Light Reactions: use solar energy to produce ATP and NADPH
for the light-independent reactions (aka Calvin Cycle)
- ATP is used for chemical energy
Light Reactions (Cyclic e- Flow)
Light-independent reactions take place in the stroma.
• In the light-independent reactions a carboxylase catalyses the carboxylation of ribulose bisphosphate.
•
Produces only ATP; no NADPH is produced
•
Occurs when [ATP] is gets low for Calvin Cycle to continue
•
Involves only Fd, Pc, and PS 1 in cyclic pattern
Light Independent Reactions (Calvin Cycle)
• Glycerate 3-phosphate is reduced to triose phosphate using reduced NADP and ATP.
• Triose phosphate is used to regenerate RuBP and produce carbohydrates.
• Ribulose bisphosphate is reformed using ATP. Calvin’s experiment to elucidate the carboxylation of RuBP.
•
Light-Independent
Reactions: uses ATP
and NADPH to convert
CO
2
to sugar
•
There are 3 parts:
1) Carbon Fixation
2) Reduction
3) Regeneration of
CO
2
acceptor
Summary of Photosynthesis
Photosynthesis uses the energy in sunlight to produce the chemical
energy needed for life.
•
Light Reactions
•
Products
•
NADPH
•
ATP
•
Oxygen
•
Dark Reaction
•
Products
Action Spectrum of Photosynthesis
• Students should know that visible light has
wavelengths between 400 and 700 nanometres, but they are not expected to recall the wavelengths of specific colours of light.
•
Which
wavelength of
light best drives
photosynthesis?
Angiosperms: Flowering Plants
•
Two basic division:
Photorespiration
Photorespiration: instead of CO
2
absorbed during the Calvin Cycle,
O
2
is absorbed by rubisco to produce CO
2
.
- “photo”= light; “respiration”= CO
2
produced
- ATP is used.
Alternatives to Carbon Fixation
Developments in scientific research follow improvements in apparatus—sources of 14C and autoradiography enabled Calvin to elucidate the pathways of carbon fixation (1.8).
•
C3: basic photosynthesis that forms a 3-Carbon compound as its
1
st
product; includes both dicots and monocots such as rice,
wheat & soybean
•
C4: forms a 4-Carbon compound as its 1
st
product; include
agriculturally important monocots…sugar cane and corn
C
4
Leaf Structure
• Developments in scientific research follow improvements in apparatus—sources of 14C and autoradiography enabled Calvin to elucidate the pathways of carbon fixation (1.8).
•
C4: two distinct types of photosynthetic cells:
1) Mesophyll cells: CO
2
incorporation occurs here
2) Bundle-sheath cells: Calvin cycle occurs here
•
Specifically useful for hot regions with a lot of sunlight
CAM Structure
Developments in scientific research follow improvements in apparatus—sources of 14C and autoradiography enabled Calvin to elucidate the pathways of carbon fixation (1.8).
•
CAM (crassulacean acid metabolism): open their stomata at night and closes
them during the day to prevent water loss.
•
Useful in arid environments and found in succulent plants.
•
Carbon fixation occurs in the same cell (mesophyll cells) but occurs at different
times.
- CO
2
incorporated during the night and stored in vacuoles. Calvin cycle occurs at
Carbon Fixation Comparisons
• Developments in scientific research follow improvements in apparatus—sources of 14C and autoradiography enabled Calvin to elucidate the pathways of carbon fixation (1.8).
•
Compare the three
types of carbon
fixation. What do
they have in
common? What
differences do they
have?
Limiting Factors
• Temperature, light intensity and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis.
•
Light Intensity: increases up to a certain point
•
Temperature: has an optimal temp; too cold or hot is
no good.
•
Concentration of CO
2:
increases to a certain point
Nature of science: Experimental design—controlling relevant variables in photosynthesis experiments is essential (3.1).
• Oxygen is produced in photosynthesis from the photolysis of water.
• Energy is needed to produce carbohydrates and other carbon compounds from carbon dioxide. • Application: Changes to the Earth’s atmosphere, oceans and rock deposition due to photosynthesis. • Skill: Separation of photosynthetic pigments by chromatograph (Practical 4).
• Skill: Design of experiments to investigate the effect of limiting factors on photosynthesis.
Guidance:
• Water free of dissolved carbon dioxide for photosynthesis experiments can be produced by boiling and cooling water. • Paper chromatography can be used to separate photosynthetic pigments but thin layer chromatography gives better results. • Absorption of light by photosystems generates excited electrons.
• Excited electrons from Photosystem II are used to contribute to generate a proton gradient. • ATP synthase in thylakoids generates ATP using the proton gradient.
• Excited electrons from Photosystem I are used to reduce NADP.
Aim 6: Hill/s method demonstrating electron transfer in chloroplasts by observing DCPIP reduction, immobilization of a culture of
an alga such as Scenedesmus in alginate beads and measurement of the rate of photosynthesis by monitoring their effect on hydrogencarbonate indicator are all possible experiments.
Utilization:
• The Global Artificial Photosynthesis (GAP) project aims to create an artificial “leaf” within the next decade. An electronic version of the leaf that creates oxygen and hydrogen from water and sunlight has already been invented and will be developed for use in the next decade.
From Topic 9.1 Understandings:
• Transpiration is the inevitable consequence of gas exchange in the leaf.
Applications and skills:
