Lecture 30 1) Photosynthesis in green plants (leaf) 2) Photosystem – contains clusters of pigment molecules (chlorophyll A + B, corotinoids) a) Light hits these and is absorbed, initiates light reactions, giving rises to chemical energy (ATP and PTH) which drives the Calvin cycle. b) Light excites electrons, when it returns it excites an adjacent pigment molecule, energy passed down pigment molecules until it reaches a reaction center chlorophyll. c) Reaction center is distinct – chlorophyll is same but molecular environment is different in that the chlorophyll donates an electron to the reaction center, which initiates the light reactions. d) (PS2 comes before PS1 – Electron transport starts with PS2 ) Diff b/w PS1 + PS2 – Different wavelength efficiencies (PS1 = 700 nm, PS2 = 680 nm). In PS1, energy is used to drive electron transport chain and NADP+ to NADPH. In PS2, energy drives the proton pump. PS1 obtains electrons from the electron transport chain associated with PS2. PS2 received electrons from oxygen and water.
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