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Chemiosmosis
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<p>Chemiosmosis is the movement of <a href="/facts/Ion/3bePpDna">ions</a> across a <a href="/facts/Semipermeable_membrane/YxENKzn5">semipermeable membrane</a> bound structure, down their <a href="/facts/Electrochemical_gradient/IEfjjoIL">electrochemical gradient</a>. An important example is the formation of <a href="/facts/Adenosine_triphosphate/nB9bwgcU">adenosine triphosphate (ATP)</a> by the movement of <a href="/facts/Hydrogen/BoYHjl0J">hydrogen</a> ions (H+) across a <a href="/facts/Inner_nuclear_membrane/IwRQ5BVL">membrane</a> during <a href="/facts/Cellular_respiration/kb6gpsvL">cellular respiration</a> or <a href="/facts/Photosynthesis/TMV7w693">photosynthesis</a>. </p> <p>Hydrogen ions, or <a href="/facts/Proton/clCjepXP">protons</a>, will <a href="/facts/Diffusion/KbAxroBa">diffuse</a> from a region of high proton concentration to a region of lower proton concentration, and an <a href="/facts/Electrochemical_gradient/IEfjjoIL">electrochemical concentration gradient</a> of protons across a membrane can be harnessed to make ATP. This process is related to <a href="/facts/Osmosis/vYPfyX76">osmosis</a>, the movement of <a href="/facts/Water/0lkXnJPK">water</a> across a selective membrane, which is why it is called "chemiosmosis". </p><p><a href="/facts/ATP_synthase/5NBMxsVX">ATP synthase</a> is the <a href="/facts/Enzyme/DSI1Fh7y">enzyme</a> that makes ATP by chemiosmosis. It allows protons to pass through the membrane and uses the <a href="/facts/Thermodynamic_free_energy/GtjtQqnq">free energy</a> difference to convert <a href="/facts/Phosphorylate/LXUEEeIL">phosphorylate</a> <a href="/facts/Adenosine_diphosphate/JEDnsCjn">adenosine diphosphate</a> (ADP) into ATP. The ATP synthase contains two parts: CF0 (present in thylakoid membrane) and CF1 (protrudes on the outer surface of thylakoid membrane). The breakdown of the proton gradient leads to conformational change in CF1—providing enough energy in the process to convert ADP to ATP. The generation of ATP by chemiosmosis occurs in <a href="/facts/Mitochondria/ErHqrdJ1">mitochondria</a> and <a href="/facts/Chloroplast/fo8U3yTx">chloroplasts</a>, as well as in most <a href="/facts/Bacteria/wC8xSCsU">bacteria</a> and <a href="/facts/Archaea/Adxh0aHw">archaea</a>. For instance, in <a href="/facts/Chloroplast/fo8U3yTx">chloroplasts</a> during photosynthesis, an electron transport chain pumps H+ ions (protons) in the <a href="/facts/Stroma_(fluid)/AYwQHKSm">stroma (fluid)</a> through the thylakoid membrane to the thylakoid spaces. The stored energy is used to <a href="/facts/Photophosphorylation/vMcaVqpy">photophosphorylate</a> ADP, making ATP, as protons move through ATP synthase. </p>