1. Photosynthesis: Using Light to Make Food
They Might Be Giants

2. New car, iPods, Cell Phones…
World’s demand for energy grows
Most energy generated from pollution-laden fossil fuels
More Power = More pollution, acid rain, greenhouse gases, and global warming.
Is there a better energy solution?
Algae Fuel

3. Photosynthesis

4. Photosynthesis occurs in chloroplasts of plant cells

5. Plants produce O2Gas by splitting water
1800’s basic equation for photosynthesis discovered.
Scientists assumed plants produced O2 by splitting CO2.
1950’s hypothesis tested using an isotope of O2

6. Fates of all the atoms in photosynthesis
Photosynthesis produces 160 billion metric tons of carbohydrate a year. Where does most of the mass of this huge amount of organic matter come from?

7. Overview: The two stages of photosynthesis are linked by ATP and NADPH

8. Visible radiation drives the light reactions

9. The interaction of light with a chloroplast
Pigments
Chlorophyll a
Absorbs: blue-violet & red
Reflects: green
Chlorophyll b
Absorbs: blue & orange
Reflects: yellow-green
Carotenoids
Various shades of yellow and orange.
Photoprotection: absorb & dissipate excessive light energy.
Only visible after green chlorophyll break down

10. Photosystems capture solar power
Pigment absorbs a photon
(1) Pigments electron’s jumps to an energy level farther from nucleus.
Electron has more potential energy.
Excited state = unstable.
Generally, when isolated pigment molecules absorb light, their excited electrons drop back down to the ground state in a billionth of a second, releasing their excess energy as heat.
Fluorescence.

14. Chemiosmosis powers ATP synthesis in light reactions

15. Overview of Calvin Cycle/Dark Reactions

16. Details of the Calvin cycle, which takes place in the stroma of a chloroplast

17. Review: Photosynthesis uses light energy, CO2, and H20 to make food molecules