The proton gradient is also called an electrochemical

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The proton gradient is also called an electrochemical gradient. In summary, the citric acid cycle leads to the generation of a proton electrochemical gradient, which is a source of potential energy. This is used to synthesize ATP. ATP synthase converts the energy of the proton gradient into the energy of ATP In 1961, Peter Mitchell proposed a hypothesis to explain how the energy stored in the proton electrochemical gradient is used to synthesize ATP. In 1978 he was awarded the Nobel Prize for work that changed how we understand energy is harnessed. For the potential energy of the gradient to be released, there must be an opening in the membrane. Protons diffuse down their electrical and concentration gradients through a transmembrane protein channel into the mitochondrial matrix. The movement must be coupled with the synthesis of ATP. This is made possible by ATP synthase. ATP synthase is composed of two subunits called F 0 and F 1 . F 0 forms the channel in the inner mitochondrial membrane. F 1 is the catalytic unit that synthesizes ATP. Bio 281 Lecture Page 4
ATP synthase. ATP synthase is composed of two subunits called F 0 and F 1 . F 0 forms the channel in the inner mitochondrial membrane. F 1 is the catalytic unit that synthesizes ATP. Proton flow through the channel causes it to rotate, converting the energy of the proton gradient into mechanical rotational energy, a form of kinetic energy. This leads to a rotation of the F 1 subunit in the mitochondrial matrix, which then causes conformational changes that allow it to catalyze the synthesis of ATP from ADP and P i . This way the energy is converted into the chemical energy of ATP. Evidence for this idea is called the chemiosmotic hypothesis , did not come for over a decade. Overall in cellular respiration, Glucose hold potential energy in the covalent bonds. Energy is released in a series of reactions and captured in chemical form. These reactions generate ATP directly by substrate-level phosphorylation. Other redox reactions transfer energy to electron carriers. These carriers donate electrons to the ETC, which uses the energy stored in the electron carriers to pump protons across the membrane. Energy of the reduced carriers is transformed into energy stored in a proton gradient. ATP synthase converts the energy of the gradient to kinetic energy, which drives the synthesis of ATP. Bio 281 Lecture Page 5