In: Clayton RK, Sistrom WR (eds) The photosynthetic bacteria.

And, once you master your knowledge of photosynthesis, you can relax in the sun with a greater appreciation for the O2 you breathe, knowing that it is produced from the photosynthetic process. Don’t forget the sunscreen—at least SPF 30—you aren’t a plant, after all. Finally, you will realize that the beachside smoothie you are sipping, along with everything else that you have ever eaten, or will ever eat, relies on photosynthesis either directly or indirectly as its source of energy. Unless, of course, you have gotten into the habit of snacking on chemoautotrophs that live in rocks or deep-sea hydrothermal vents. They don't use photosynthesis.

Section 19.3 Two Photosystems Generate a Proton Gradient and NADPH in Oxygenic Photosynthesis
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During this process, ATP is generated by the Photosystem II electron transport chain and . According to the chemiosmosis theory, as the electrons are transported down the electron transport chain, some of the energy released is used to pump protons across the thylakoid membrane from the stroma of the chloroplast to the thylakoid interior space producing a proton gradient or proton motive force. As the accumulating protons in the thylakoid interior space pass back across the thylakoid membrane to the stroma through ATP synthetase complexes, this proton motive force is used to generate ATP from ADP and Pi (see Fig. 2 and Fig. 3).


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McGraw-Hill Flash animation illustrating photosynthetic electran transport and ATP production by ATPsynthase
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Cyclic photophosphorylation occurs less commonly in plants than noncyclic photophosphorylation in plants, probably when there is too little NADP+ available. It is also seen in certain photosynthetic bacteria. Cyclic photophosphorylation involves only Photosystem I and generates ATP but not NADPH. As the electrons from the reaction center of Photosystem I are picked up by the electron transport chain, they are transported back to the reaction center chlorophyll. As the electrons are transported down the electron transport chain, some of the energy released is used to pump protons across the thylakoid membrane from the stroma of the chloroplast to the thylakoid interior space producing a proton gradient or proton motive force. As the accumulating protons in the thylakoid interior space pass back across the thylakoid membrane to the stroma through ATP synthetase, this energy is used to generate ATP from ADP and Pi.


electrochemical proton gradient, ..

Photophosphorylation is the production of ATP using the energy of sunlight. Photophosphorylation is made possible as a result of chemiosmosis. Chemiosmosis is the movement of ions across a selectively permeable membrane, down their concentration gradient. During photosynthesis, light is absorbed by chlorophyll molecules. Electrons within these molecules are then raised to a higher energy state. These electrons then travel through Photosystem II, a chain of electron carriers and Photosystem I. As the electrons travel through the chain of electron carriers, they release energy. This energy is used to pump hydrogen ions across the thylakoid membrane and into the space within the thylakoid. A concentration gradient of hydrogen ions forms within this space. These then move back across the thylakoid membrane, down their concentration gradient through ATP synthase. ATP synthase uses the energy released from the movement of hydrogen ions down their concentration gradient to synthesise ATP from ADP and inorganic phosphate.

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Each antenna complex is able to trap light and transfer energy to a complex of chlorophyll molecules and proteins called the reaction center. Photons are absorbed by chlorophyll and accessory pigments and that energy is eventually transfered to the reaction center where it is absorbed by an excitable electron moving it to a higher energy level. Here the electron can be accepted by an electron acceptor molecule of an electron transport chain where the light energy is converted to chemical energy by chemiosmosis.

25/03/2005 · There is no mechanism to do it directly

Each antenna complex is able to trap light and transfer energy to a complex of chlorophyll molecules and proteins called the reaction center (see Fig. 1). As photons are absorbed by chlorophyll and accessory pigments, that energy is eventually transfered to the reaction center where, when absorbed by an excitable electron, moves it to a higher energy level. Here the electron may be accepted by an electron acceptor molecule of an electron transport chain (see Fig. 1) where the light energy is converted to chemical energy by .