BIOLOGY 220 LECTURE #13 - PHOTOSYNTHESIS I AND II - 10-11-07

BIOLOGY 220 LECTURE #13 - PHOTOSYNTHESIS I AND II -...

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BIOLOGY 220 LECTURE #13 – PHOTOSYNTHESIS I – 11/11/07 IV. Two photosystems works together in most plants A. Photosystem I is used by bacteria Photosystem II ejects an electron as soon as it is hit by an electron with wavelength of 680 nm (chlorophyll-A) 2.) The job of plastoquinone is to catch the excited electron and send the electron to something that can utilize the energy. Cytochrome b6-f is one of those things. Cytochromes are really common in any energetic system o b6-f takes the electron from plastoquinone and it takes some energy from the electron and it uses that energy to pump a proton. o A gradient is energy and we’re going to use energy to make ATP. Then plastoquinone hands the electron to plastocyanin. - Plastocyanin takes the electron and it hands it to the next photosystem. Photosystem I gets an electron from the previous photosystem. All of these carrier molecules have a metal at the center. o The metal grabs and holds the electron to move it from place to place NADP reductase is going to adhere an electron onto a molecule called NADP and then grab a H and adhere it to produce NADPH. o This NADPH molecule allows us to store energy for use later. At plastoquinone, plastocyanin, and ferodoxine (carrier molecules), the energy absorbed by these carrier molecules is lost (no utilization). b6-f pumps a proton and NADP forms NADPH from the energy of an excited electron SUMMARY for this section (“non-cyclic” photophosphorylation: We get an ATP from the proton we pumped and we also get NADPH We are turning light energy into stored chemical energy in the form of ATP and NADPH Photophosphorylation – means we are making ATP with light All of the accumulating protons form a gradient and the gradient can be use to form ATP with the help of ATP synthase (same ATP synthase from respiration) “What are the two sources of H+s accumulating inside the thylakoid?”
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1 st source is the b6-f complex pumps a proton and pulls a proton from outside the thylakoid and brings it in (pumping from the energy of the electron) 2 nd Source: Every time we split a water, we get two protons V. “Cyclic” photophosphorylation What happens is that you keep recycling the same electron. We are making ATP…are we making NADPH?
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BIOLOGY 220 LECTURE #13 - PHOTOSYNTHESIS I AND II -...

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