The overall process of creating energy in this fashion is termed oxidative phosphorylation. In respiring bacteria under physiological conditions, ATP synthase, in general, runs in the opposite direction, creating ATP while using the proton motive force created by the electron transport chain as a source of energy. The electrochemical potential difference between the two sides of the membrane in mitochondria, chloroplasts, bacteria, and other membranous compartments that engage in active transport involving proton pumps, is at times called a chemiosmotic potential or proton motive force. The combination of these two factors determines the thermodynamically favorable direction for an ion’s movement across a membrane. Second, a chemical component is caused by a differential concentration of ions across the membrane. First, the electrical component is caused by a charge difference across the lipid membrane. An electrochemical gradient has two components. This potential energy is used for the synthesis of ATP by phosphorylation. In the mitochondria and chloroplasts, proton gradients are used to generate a chemiosmotic potential that is also known as a proton motive force. In biological processes, the direction an ion moves by diffusion or active transport across a membrane is determined by the electrochemical gradient. Figure: The Basics of Redox: In every redox reaction you have two halves: reduction and oxidation.Īn electrochemical gradient represents one of the many interchangeable forms of potential energy through which energy may be conserved. In animal cells, the mitochondria performs similar functions. This then drives the synthesis of adenosine triphosphate ( ATP ) and is maintained by the reduction of oxygen, or alternative receptors for anaerobic respiration. As intermediate steps, the reduced carbon compounds are used to reduce nicotinamide adenine dinucleotide (NAD+), which then contributes to the creation of a proton gradient. The reverse reaction, respiration, oxidizes sugars (loses an electron) to produce carbon dioxide and water. Photosynthesis involves the reduction of carbon dioxide into sugars and the oxidation of water into molecular oxygen. Reduction occurs when an oxidant gains an electron. \)īiological energy is frequently stored and released by means of redox reactions, or the transfer of electrons.
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