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The generation of ATP by chemiosmosis occurs in mitochondria and chloroplasts, as well as in most bacteria and archaea. For instance, in chloroplasts during photosynthesis, an electron transport chain pumps H + ions (protons) in the stroma (fluid) through the thylakoid membrane to the thylakoid spaces.
A proton gradient is created across the thylakoid membrane (6) as protons (3) are transported from the chloroplast stroma (4) to the thylakoid lumen (5). Through chemiosmosis, ATP (9) is produced where ATP synthase (1) binds an inorganic phosphate group (8) to an ADP molecule (7).
Energy from PSI drives this process [citation needed] and is harnessed (the whole process is termed chemiosmosis) to pump protons across the membrane, into the thylakoid lumen space from the chloroplast stroma.
Oxidative phosphorylation is made up of two closely connected components: the electron transport chain and chemiosmosis. The electron transport chain in the cell is the site of oxidative phosphorylation. The NADH and succinate generated in the citric acid cycle are oxidized, releasing the energy of O 2 to power the ATP synthase.
This transport chain produces a proton-motive force, pumping H + ions across the membrane and producing a concentration gradient that can be used to power ATP synthase during chemiosmosis. This pathway is known as cyclic photophosphorylation, and it produces neither O 2 nor NADPH.
André Tridon Jagendorf (October 21, 1926 – March 13, 2017) was an American Liberty Hyde Bailey Professor Emeritus in the Section of Plant Biology [1] [2] [3] at Cornell University who is notable for providing direct evidence that chloroplasts synthesize adenosine triphosphate (ATP) using the chemiosmotic mechanism proposed by Peter Mitchell.
In biology, electrochemical gradients allow cells to control the direction ions move across membranes. In mitochondria and chloroplasts, proton gradients generate a chemiosmotic potential used to synthesize ATP, [1] and the sodium-potassium gradient helps neural synapses quickly transmit information. [citation needed]
An uncoupler or uncoupling agent is a molecule that disrupts oxidative phosphorylation in prokaryotes and mitochondria or photophosphorylation in chloroplasts and cyanobacteria by dissociating the reactions of ATP synthesis from the electron transport chain.