1. Photosynthesis!!!!

2. Photosynthesis is divided into two parts
The overall reaction in photosynthesis:
Light
energy
6CO2 +
12 H2O +
C6H12O6 +
6O2 +
6 H2O
Two components:
Light-dependent reactions
Light-independent reactions
Chemical energy
(ATP, NADPH)
Light
energy
Chemical energy
(ATP, NADPH)
Chemical energy
(C6 H12O6)
H2O O2
CO2
Energy Harvest
Synthesis

3. Figure An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle (Layer 3)

4. Photosynthesis starts in the thylakoid membrane
These aggregations of pigment molecules are called photosystems

5. Figure 10.11 How a photosystem harvests light

6. The energy from light is captured and converted in chloroplasts
Energy from light excites an electron in chlorophyll. This electron is then passed to acceptor molecules to be used to make ATP and NADPH
Stroma
Light photon
Electron acceptor molecule e-
Reaction center
(chlorophyll a )
Thylakoid
Thylakoid space
Chloroplast
Photosystem
Stroma

7. There are 2 types of reaction centers in green algae and plants:
Photosystem I: activated by light of wavelengths of 700nm
Photosystem II: activated by light of wavelengths of 680nm
These photosystems are named after the order in which they were discovered, not the order in which they act during photosynthesis
Figure: 7.6c
Caption:
(c) In chloroplasts, excited electrons transmit energy to a reaction center. There the electron is captured by an electron acceptor that becomes reduced. As a result, fluorescence is rare.

8. Noncyclic electron flow during the light reactions generates ATP and NADPH

9. The electrons in photosystem II are replaced by electrons from water

10. The electrons from chlorophyll are passed to an ETC which makes ATP

11. The electrons reach photosystem I where another photon of light excites them once again

12. The electrons from photosystem II are passed down a second ETC, in which they are used to make NADPH

13. Figure 10.13 A mechanical analogy for the light reactions

14. Figure 10.16 The light reactions and chemiosmosis: the organization of the thylakoid membrane

15. Figure 10.15 Comparison of chemiosmosis in mitochondria and chloroplasts

16. Sometimes an alternate pathway happens
In cyclic electron transport, which drives cyclic photophosphorylation,
photosystem I transfers electrons to plastoquinone (PQ).

17. Summary of the Light Dependent Reaction of Photosynthesis
Light energy is absorbed by chlorophyll molecules, which excites electrons
The energy from the excited electrons is converted to chemical energy:
Photosystem II:
electron transport chain produces ATP
The excited electrons are replaced by splitting a water molecule, releasing O2
Photosystem I:
The excited electron is donated to NADP+ to produce NADPH

18. Photosynthesis is a two-step process
The light independent reactions (Calvin cycle) use the energy in ATP and NADPH to reduce organic compounds to form glucose.

19. Figure 10.17 The Calvin cycle (Layer 1)

20. Figure 10.17 The Calvin cycle (Layer 2)

21. Figure 10.17 The Calvin cycle (Layer 3)

22. Summary Light Dependent Reaction
Light + chlorophyll --> ATP + NADPH + (O2 as waste)
Light Independent Reaction (Calvin Cycle)
CO2 + ATP + NADPH --> glucose

23. What happens to the glucose produced by photosynthesis?
Sucrose
CH2OH O O H H
HOCH2 H H OH H O H HO
Figure: 7.17a
Caption:
(a) In plants, sugars are usually transported in the form of sucrose. 
CH2OH HO H OH HO H
Fructose subunit
Glucose subunit

24. Starch Glucose subunit Glucose subunit Glucose subunit CH2OH CH2OH
Up to 1000 or more monomers H H H O OH H O OH H O OH H O H OH H OH H OH
Figure: 7.17b
Caption:
(b) Plants store sugars in the form of starch, which consists of long chains of glucose molecules.
Glucose subunit
Glucose subunit
Glucose subunit