photosynthesis
TRANSCRIPT
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Photosynthesis
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The Basic Facts
• It is the conversion of light energy into chemical potential energy.
• The energy is stored in organic molecules (e.g. ATP and glucose)
• Carbon dioxide is reduced to produce carbohydrate
• So, it needs a supply of electrons hydrogens and energy!
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Chloroplast Structure
1. outer membrane2. intermembrane space3. inner membrane (1+2+3:
envelope)4. stroma (aqueous fluid)
5. thylakoid lumen (inside of thylakoid)
6. thylakoid membrane7. granum (stack of
thylakoids)
8. thylakoid (lamella)9. starch10. ribosome11. plastidial DNA12. plastoglobule (drop of lipids)
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Light dependent stage
(on thylakoid membranes)
• The aim is to produce a supply of ATP (energy) and electrons that can be used to reduce carbon dioxide.
• The electrons are carried by NADP (called reduced NADP or NADPH when it is carrying electrons).
• Oxygen is released as a waste product.
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Or put a different way…
light dependent
reaction
ADP + P ATP
NADPNADPH
water oxygen
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This is a blank slide for Mr King to do his own drawing on
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Photolysis
• Using light energy to split water into electrons, hydrogen ions and water.
• H2O H+ + e- + O2
• Replacing the electrons and hydrogen ions now carried by NADPH
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summary• Chlorophyll absorbs light energy
and its electrons are ‘excited’• ‘excited’ electrons pass through a
series of carriers releasing energy to generate ATP from ADP and P (photophosphorylation)
• Electrons are picked up by NADP• Light energy splits water and the
electrons are used to replace missing electrons in chlorophyll
• This all happens on membranes.
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Light Independent stage
• Energy from ATP, hydrogens and electrons from reduced NADP are used to reduce carbon dioxide to produce carbohydrate.
• This happens in the stroma.
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Light independent stage
light independent
reaction
Reduced NADP
NADP
Carbon dioxide
ATP ADP + Pi
glucose
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Ribulose Biphosphate
2X Glycerate-3-Phosphate
2X Triose Phosphate
Glucose
(1C)
(5C)
(3C)
(3C)
(6C)
NADPH
ATP
ATP
CO2
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What happens without light?
• Which stages can still continue when the light is turned off?
• Which molecules will build up when the light is turned off?