Photosynthesis: Using Light to Make Food They Might Be Giants

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

Photosynthesis

Photosynthesis occurs in chloroplasts of plant cells

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

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?

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

Visible radiation drives the light reactions

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

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.

Chemiosmosis powers ATP synthesis in light reactions

Overview of Calvin Cycle/Dark Reactions

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

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