Oxidative phosphorylation is a metabolic pathway that uses energy released by the oxidation of nutrients to produce adenosine triphosphate (ATP). Although many forms of life on earth using various types of nutrients, almost all carry out oxidative phosphorylation to produce ATP. This track is very commonly used because it is a very efficient way to release some energy, as compared to other alternatives such as fermentation anaerobic glycolysis.
Electron transport chain in mitochondria is the site of oxidative phosphorylation in eukaryotes. NADH and succinate generated in the citric acid cycle is oxidized, releasing energy for use by the ATP synthase.
During oxidative phosphorylation, electrons are transferred from the electron donor to the electron acceptor through redox reactions. The redox reactions that release energy used to make ATP. In eukaryotes, these redox reactions carried out by a complex series of proteins in the mitochondria, when in prokaryotes, these proteins are in the cell membrane. The enzymes that are interconnected is referred to as the electron transport chain. In eukaryotes, five main protein complexes involved in this process, when in prokaryotes, there are many different enzymes that are involved.
The energy released by the movement of electrons through the electron transport chain is used to transport protons across the membrane of mitochondria. This process is called chemiosmosis. The transport of potential energy in the form of a pH gradient and an electrical potential along the membrane. The energy stored in the form utilized by allowing protons to flow back across the membrane through an enzyme called ATP synthase. This enzyme uses this energy to generate ATP from adenosine diphosphate (ADP) through the phosphorylation reaction. This reaction is driven by the flow of protons, which encourages rotation of one part of the enzyme.
Although oxidative phosphorylation is a vital part of metabolism, it produces reactive oxygen species such as superoxide and hydrogen peroxide. This can lead to the formation of free radicals, damage cells, and may also cause aging. The enzymes involved in these metabolic pathways are also a target of many drugs and toxins that can inhibit enzyme activity.
Overview of Energy Transfer Through chemiosmosis
Oxidative phosphorylation works by using chemical reactions that produce energy to drive reactions that require energy. Both sets of reactions are said to join. This means that one can not walk without a reaction other reactions. The flow of electrons through the electron transport chain is exergonic process, releasing the energy, when the synthesis of ATP is an endergonic process, which requires energy. Good electron transport chain and ATP synthase present in the membrane, and the energy transferred from the electron transport chain to ATP synthase proton movement across the membrane through this. This process is called chemiosmosis. [1] In practice, this is similar to an electrical circuit, driven by proton flow from the negative side to the positive side of the membrane by a proton-pumping enzymes that of the electron transport chain. This enzyme such as batteries. The movement of protons creates an electrochemical gradient along the membrane, which is often called the force proton (proton-motive force). This gradient has two components: the difference in proton concentration (pH gradient) and the difference in electrical potential. Stored energy in the form of electrical potential differences in the mitochondria, as well as a pH gradient in chloroplasts. [2]
ATP synthase releases this stored energy to complete the circuit and allow protons to flow back to the negative side of the membrane. [3] This enzyme such as electric motors, which use proton motive power to drive the rotation of the structure and use this movement to synthesize ATP.
The energy released by oxidative phosphorylation is quite high compared to the energy released by anaerobic fermentation. Glycolysis produces only 2 ATP molecules, whereas the oxidative phosphorylation 10 with 2 molecules of NADH molecules formed succinate conversion of one molecule of glucose into carbon dioxide and water, produced 30 to 36 molecules of ATP. [4] The yield of ATP is actually a maximum theoretical value : in practice, the resulting ATP is lower than that value. [5]
Molecular electron and proton transfer
Electron transport chain carries both protons and electrons, proton transport from donor to acceptor, and run through the membrane proton transport. This process uses a soluble molecule and molecule bound to the transfer. In the mitochondria, electrons are transferred in the intermembrane space using electron transfer protein cytochrome c is soluble in water. [6] He was just transporting electrons, and these electrons are transferred using the reduction and oxidation of iron atoms bound to the protein in the heme group structure. Cytochrome c is also found in some bacteria, where it is located in the periplasmic space. [7]
In the inner membrane of mitochondria, coenzyme Q10 carrier lipid-soluble electron carries both electrons and protons using a redox cycle. [8] benzokuinon small molecule is very hydrophobic, so it will diffuse freely into the membrane. When Q receives two electrons and two protons, he became ubikuinol reduced form (QH2); when the QH2 releases two electrons and two protons, it is oxidized back into shape ubikuinon (Q). Consequently, if the two enzymes are prepared so universally Q is reduced on one side of the membrane and QH2 oxidized on the other hand, ubikuinon will confront these reactions and shuttle protons across the membrane repeat. [9] Some of the bacterial electron transport chain use different quinones, such menakuinon, besides ubikuinon . [10]
In proteins, electron transfer between the flavin cofactor, [11] [3] iron-sulfur clusters, and cytochromes. There are several types of iron-sulfur clusters. The simplest types are found in the electron transfer chain consists of two iron atoms are linked by two sulfur atoms; This is referred to as the cluster [2Fe-2S]. The second type, called a [4Fe-4S], sebua cube containing four iron atoms and four sulfur atoms. Each atom in the cluster is coordinated by amino acids, usually coordination between the sulfur atoms with Cysteine. Metal ion cofactors undergo redox reactions without binding or releasing protons, so that the electron transport chain it only serves as an electron carrier. Electrons move far enough through these proteins by jumping around the cofactor chain. [12] This occurs through quantum tunneling, which occurs rapidly at distances smaller than 1.4 × 10-9 m. [13]
Electron transport chain of eukaryotic
Many catabolic biochemical processes, such as glycolysis, the citric acid cycle and beta oxidation, resulting in the reduced coenzyme NADH. Coenzyme contains electrons that have a high transfer potential. In other words, he would release enormous energy during oxidation. However, the cell will not release all this energy at the same time because it will be uncontrolled reaction. Instead, electrons are removed from NADH and transferred to oxygen through a series of enzyme that will release a small amount of energy in each of these enzymes. Which consists of a series of enzyme complexes I through IV complex is referred to as the electron transport chain and is found in the inner mitochondrial membrane.
1. Complex I (NADH dehydrogenase)
2. Complex II: succinate-Q oxidoreductase.
3. Complex 3 (Q-cytochrome c oxidoreductase)
4. Complex IV: Cytochrome C oxidase.
5. Complex V (ATP synthase)
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