Light in the violet blue and red portions of the

Unformatted text preview: lue or red light. Light in the violet-blue and red portions of the spectrum are most effective in driving photosynthesis. 2 PIGMENTS: chlorophyll molecules CH3 CHO CH2 CH C H3C H H3C C H C CH2 CH2 C O CH2 O O CH3 C C C C N C H H C C O C N Mg N C C C C C O CH3 H C C N CH3 C C C C H CH2 CH3 in chlorophyll a in chlorophyll b PIGMENTS: Carotenoids -carotene, a "carotenoid" Porphyrin ring: isoprene Unsaturated hydrocarbon, lipophilic (Structure similar to vitamin A, and to retinal, a visual pigment) Accessory pigments: pass energy to chlorophyll, not directly to photosynthesis electron transport system. They also protect chlorophylls from damaging light. Hydrocarbon tail: Absorption spectra of pigments When a pigment absorbs a photon, an electron is elevated to a higher energy level FLUORESCENCE Red (low energy) light Blue (high energy) light chlorophyll fluorescing Light reaction linear electron transport chain has two photosystems, II and I high Photosystem I Photosystem II Energy of electron 4 low water is split electrons enter PS II H+ remain in lumen, O2 given off Cyclic electron flow ATP, but no NADPH 3 Electrons are carried by the dinucleotide NADP Photosystems are complex aggregations of many molecules Photosystem II NADP (oxidized) + 2H+ + 2e- NADP (reduced) se NADP Nicotinamide adenine dinucleotide phosphate stroma Photosystem II, PQ, cytochrome pump protons into the lumen light reactions are coupled to chemiosmosis in the thylakoid membrane LIGHT NADP+...
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