1. Photosynthesis
Packet #30
Chapter #10

2. Introduction Photosynthesis Photo--”light”
The process of storing energy from the sun in the form of glucose
The process of making sugar (glucose) using light energy
Photo--”light”
Synthesis--”make” ; “put together”
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3. Introduction II
Nourishes almost all of the living world directly or indirectly
Based on the food chain/web
More to come later in the course
Chemical Equation for Photosynthesis
6CO2 + 12H2O + Light Energy --> C6H12O6 + 6O2 + 6H2O
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4. Structure of Leaf

5. Structure of Chloroplasts

6. Events of Photosynthesis
The Light Reactions
Photo part of photosynthesis
Calvin Cycle
Synthesis part
Sugar is synthesized
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7. Light Reactions

8. Light Reactions “Photo” part of photosynthesis
Convert solar energy to chemical energy
Composed four distinctive parts
Photosystem II
Electron Transport Chain I
Photosystem I
Electron Transport Chain II
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9. Light Reactions II
The goal of the light reactions is to produce ATP and NADPH via the movement of electrons
The ATP, and NADPH, produced is used in the Calvin Cycle.

10. Photosystems The photosystems first responsibility is to absorb light.
Photosystem II
Absorbs light with wavelengths of 680 nM
Photosystem I
Absorbs light with wavelengths of 700 nM
The second function of the photosystems is to remove electrons and then move them to the electron transport chains.
Special Note
Oxygen, a waste product as a result of photosynthesis, is produced by the removal of electrons from H2O in photosystem II

11. Photosystems II
Photon, of a specific wavelength, hits a chlorophyll molecule and causes an electron to become excited.

12. Photosystems III
The excited electron bounces around until it reaches special chlorophyll molecules located in the reaction center.
Electrons, once in the reaction center, move to the primary electron acceptor.
Electrons then move onto an electron transport chain.

13. Light Reactions I Overall
Inputs
Light
NADP+
ADP P
H2O
Outputs
ATP
NADPH O2
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14. Light Reactions The Flow of Electrons
Cyclic vs. Non-cyclic Flow

15. Non-Cyclic Electron Flow
Non-cyclic electron flow, as the name implies, is the movement, and use of electrons, once through the parts of the light reactions, to produce ATP and NADPH.
All four parts (steps), of the light reactions, are used.

16. Non-Cyclic Electron Flow I
Photosystem II
The reaction center drives an oxidation-reduction reaction (Redox Reaction) that helps in the formation of oxygen.
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17. Non-Cyclic Electron Flow II
Electron Transport Chain I
ATP produced will be used in the Calvin Cycle
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18. Non-Cyclic Electron Flow III
Photosystem I
Continues the movement of electrons
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19. Non-Cyclic Electron Flow IV
Electron Transport Chain II
NADPH produced will be used in the Calvin Cycle
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20. Cyclic Electron Flow
Only uses photosystem I and part of Electron Transport Chain I
Produces ATP but no NADPH or O2
Used to “make-up” the necessary amount of ATP’s for the Calvin Cycle
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21. The Calvin Cycle
“Dark Reactions”

22. Calvin Cycle “Dark Reactions”
Synthesis of photosynthesis
Makes sugar
ATP and NADPH are used to convert CO2 to sugar
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23. Calvin Cycle Overall Inputs Outputs CO2 H2O ATP NADPH Sugars (Glucose)
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24. Calvin Cycle Sequence of Events
Carbon Fixation
Use of carbon dioxide
Reduction
1, 3 bisphosphoglycerate is reduced to the sugar G3P
6 ATP’s is used
Reduced using the electrons produced by the oxidation of NADPH
Regeneration of CO2 Acceptor
This acceptor, RuBP, is then re-used in carbon fixation to continue the next cycle of the Calvin Cycle
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25. Calvin Cycle I
Carbon Fixation

26. Calvin Cycle II
Reduction

27. Calvin Cycle III
Regeneration of CO2 Acceptor