Proton gradient that drives atp synthesis11/11/2023 ![]() ![]() In brief, the hypothesis was that most adenosine triphosphate (ATP) synthesis in respiring cells comes from the electrochemical gradient across the inner membranes of mitochondria by using the energy of NADH and FADH 2 formed during the oxidative breakdown of energy-rich molecules such as glucose. Mitchell proposed the chemiosmotic hypothesis in 1961. The stored energy is used to photophosphorylate ADP, making ATP, as protons move through ATP synthase. 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. 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 mitochondria and chloroplasts, as well as in most bacteria and archaea. The ATP synthase contains two parts: CFo( present in thylakoid membrane) and CF1( protrudes on the outer surface of thylakoid membrane). It allows protons to pass through the membrane and uses the free energy difference to convert phosphorylate adenosine diphosphate (ADP)into ATP. This process is related to osmosis, the movement of water across a selective membrane, which is why it is called "chemiosmosis".ĪTP synthase is the enzyme that makes ATP by chemiosmosis. Hydrogen ions, or protons, will diffuse from a region of high proton concentration to a region of lower proton concentration, and an electrochemical concentration gradient of protons across a membrane can be harnessed to make ATP. ![]() 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.Īn ion gradient has potential energy and can be used to power chemical reactions when the ions pass through a channel (red). Electrochemical principle that enables cellular respirationĬhemiosmosis is the movement of ions across a semipermeable membrane bound structure, down their electrochemical gradient. ![]()
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