1. Chapter 8
Photosynthesis

2. 8-3 The Reactions of Photosynthesis
Inside the Chloroplast
Thylakoids – Sac like membrane structures inside the chloroplasts
Grana – Stacks of Thylakoid disks.
Sites of the “Light Dependent Reaction”
Stroma – Fluid filled space outside the Thylakoids
Site of the “Light Independent Reaction” or “Calvin Cycle”

3. 8-3 The Reactions of Photosynthesis

4. 8-3 The Reactions of Photosynthesis
NADPH
Nicatinamide Adenine Dinucleotide Phosphate – “Carrier Molecule”
Molecule – Transfers high energy electrons from the chlorophyll to other molecules.
Carries Hydrogen Ions (H+) H
NADP

5. 8-3 The Reactions of Photosynthesis
Light-Dependent Reactions
Requires light
Occurs in the Thylakoids
H2O is split
O2 is given off as waste
NADP picks up H+ and carries to the Calvin Cycle
ADP picks up a Phosphate & converted to ATP, which is taken to the Calvin Cycle

6. Figure 8-7 Photosynthesis: An Overview
Section 8-3
H2O O2
Sugars
CO2
Light
Chloroplast
Chloroplast
NADP+
ADP + P
Light-
Dependent
Reactions
Calvin
Cycle
ATP
NADPH
Go to Section:

7. 8-3 The Reactions of Photosynthesis
Light-Dependent Reactions
3 step process
Photosystem II
Electron Transport Chain (ETC)
Photosystem I

8. 8-3 The Reactions of Photosynthesis
Light-Dependent Reactions
Photosystem II (discovered 2nd)
Light is absorbed by chlorophyll
Water is split – O2 given off as waste

9. 8-3 The Reactions of Photosynthesis
Light-Dependent Reactions
Electron Transport Chain
High Energy Electrons (H+) travel down the Electron Transport Chain (ETC)
Provides energy for channel proteins to pump H+ inside the thylakoid membrane

10. 8-3 The Reactions of Photosynthesis
Light-Dependent Reactions
Photosystem I (discovered 1st)
Chlorophyll absorbs more light energy which is used to convert NADP+ into NADPH (taken to Calvin Cycle)
H+ inside the thylakoid pass through ATP synthase (channel protein)
Energy is used to convert ADP into ATP (taken to Calvin Cycle)

11. Figure 8-10 Light-Dependent Reactions
Section 8-3
Hydrogen
Ion Movement
Photosystem II
Chloroplast
ATP synthase
Inner
Thylakoid
Space
Thylakoid
Membrane
Stroma
Electron
Transport Chain
Photosystem I
ATP Formation
Go to Section:

12. 8-3 The Reactions of Photosynthesis
Light Independent Reaction - “Calvin Cycle”
CO2 enters the stroma
NADPH drops off H+
NADP returns to thylakoid
ATP provides energy to run Calvin Cycle
ADP return to thylakoid
CO2 and H combine to make sugar C6H12O6

13. Figure 8-7 Photosynthesis: An Overview
Light
H2O O2
Sugars
CO2
Chloroplast
Chloroplast
NADP+
ADP + P
Light-
Dependent
Reactions
Calvin
Cycle
ATP
NADPH
Go to Section:

14. 8-3 The Reactions of Photosynthesis
Light Independent Reaction - “Calvin Cycle”
Steps
CO2 enters the Calvin Cycle
6CO2 combine with six 5 carbon molecules to produce twelve three carbon molecules
Energy Input – From ATP and NADPH
One 6 Carbon sugar molecule produced
Two 3 carbon molecules combine with H (from NADPH) to form one C6H12O6
5 Carbon molecules regenerated
ten remain 3 carbon molecules are converted back into six 5 carbon molecules
H2O is reformed and released through transpiration

15. Figure 8-11 Calvin Cycle Section 8-3 CO2 Enters the Cycle Energy Input
ChloropIast
5-Carbon
Molecules
Regenerated
6-Carbon Sugar
Produced
Sugars and other compounds
Go to Section:

16. 8-3 The Reactions of Photosynthesis
Light Dependent Reaction
Energy
Light
Reactants (What comes in)
H2O
NADP
ADP
Products (What goes out) O2
NADPH
ATP
Calvin Cycle
Energy
ATP
NADPH
Reactants (What comes in)
CO2
Products (What goes out)
C6H12O6
NADP
ADP

17. 8-3 The Reactions of Photosynthesis
Factors Affecting Photosynthesis
Availability of water
Temperature
Amount of light
Intensity of light