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Chemiosmosis is the movement of ions across a semipermeable membrane bound structure, down their electrochemical gradient.An important example is the formation of adenosine triphosphate (ATP) by the movement of hydrogen ions (H +) across a membrane during cellular respiration or photosynthesis.
Glycolysis produces only 2 ATP molecules, but somewhere between 30 and 36 ATPs are produced by the oxidative phosphorylation of the 10 NADH and 2 succinate molecules made by converting one molecule of glucose to carbon dioxide and water, [6] while each cycle of beta oxidation of a fatty acid yields about 14 ATPs. These ATP yields are ...
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.
The ATP generated in this process is made by substrate-level phosphorylation, which does not require oxygen. Fermentation is less efficient at using the energy from glucose: only 2 ATP are produced per glucose, compared to the 38 ATP per glucose nominally produced by aerobic respiration. Glycolytic ATP, however, is produced more quickly.
This gradient is used by the F O F 1 ATP synthase complex to make ATP via oxidative phosphorylation. ATP synthase is sometimes described as Complex V of the electron transport chain. [10] The F O component of ATP synthase acts as an ion channel that provides for a proton flux back into the mitochondrial matrix. It is composed of a, b and c ...
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).
The structure of the intact ATP synthase is currently known at low-resolution from electron cryo-microscopy (cryo-EM) studies of the complex. The cryo-EM model of ATP synthase suggests that the peripheral stalk is a flexible structure that wraps around the complex as it joins F 1 to F O.
The energy resulting from the flux of protons back into the matrix is used by ATP synthase to combine inorganic phosphate and ADP. [6] [2]: 743–745 Similar to the electron transport chain, the light-dependent reactions of photosynthesis pump protons into the thylakoid lumen of chloroplasts to drive the synthesis of ATP. The proton gradient ...