1. 8.3 The Reactions of Photosynthesis

2. Pigments Pigments: molecules that reflect/absorb light energy
Chlorophyll a and b
Contained in chloroplasts
Contains photo-sensitive membrane that can capture solar energy
Reflects green light & absorbs all other colors
Capture slightly different wavelengths of energy
Accessory pigments
Other colors also capture sunlight; pass energy to chlorophyll
Xanthophylls, carotenoids

3. Chloroplasts
In a plant
Micrograph of a chloroplast

4. Chloroplasts Structure

5. Photosynthesis Photosynthesis: Reactants and Products Light Energy
Section 8-2
Light Energy
Chloroplast
CO2 + H2O
Sugars + O2

6. Light-Dependent Reactions
Take place only in light
Four steps
Light absorption
Electron transport
Breaking of water/oxygen production
ATP formation

7. Light-Independent Reactions
Do not require light
Calvin Cycle
Uses carbon dioxide
Forms glucose molecule

8. The Photosynthesis Equation
light
6CO2 + 6H2O C6H12O6 + 6O2
Carbon Water Glucose Oxygen
Dioxide (Sugar)
Photosynthesis uses the energy from sunlight to convert water and carbon dioxide into high-energy sugars and oxygen

10. Energy Shuttling
Recall ATP: One phosphate group removed to liberate lots of energy = superb molecule for shuttling energy around within cells.
NADP+, NADPH also shuttles energy

11. Light-dependent Reactions (Thylakoid)
Photosystem: light capturing unit containing chlorophyll
Electron transport system: electron carrier molecules that shuttle electrons, energy released to make ATP
Electrons in chlorophyll must be replaced by electrons from water so that cycle may continue; oxygen is liberated from the light reactions
Light reactions make ATP and NADPH used to fuel the reactions of the Calvin cycle (light independent reactions)

14. Calvin Cycle (light independent or “dark” reactions) (STROMA)
ATP and NADPH from light reactions used to break CO2 apart, then reassemble the carbons into glucose.
Called carbon fixation: taking carbon from an inorganic molecule (atmospheric CO2) and making an organic molecule out of it (glucose)

16. Homework Assignment: due 2/11/13
In your comp book:
Label the parts of a chloroplast on diagram provided p. 231
Organize information:
Light-dependent reactions
Light-independent reactions
Definition
Where take place
Reactants
Products