Oxidative phosphorylation equation

Every day, we build bones, move muscles, eat food, think, and perform many other activities with our bodies. All of these activities are based upon chemical reactions. However, most of these reactions are not spontaneous i. Hence, the body needs some sort of "free-energy currency," Figure 1 a molecule that can store and release free energy when it is needed to power a given biochemical reaction.

Just as purchasing transactions do not occur without monetary currency, reactions in the body do not occur without energy currency. How does the body "spend" free-energy currency to make a nonspontaneous reaction spontaneous? The answer, which is based on thermodynamics, is to use coupled reactions. The answer, from biology, is found in glycolysis and the citric-acid cycle.

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Once again, coupled reactions are key. What mechanism does the body use to couple the reducing agent reactions and the generation of ATP? ATP is synthesized primarily by a two-step process consisting of an electron-transport chain and a proton gradient.

This process is based on electrochemistry and equilibrium, as well as thermodynamics. The body satisfies it's never-ending need for energy through an elegant combination of processes that illustrate the principles of thermodynamics, electrochemistry and equilibrium.

Coupled reactions are frequently used in the body to drive important biochemical processes. Separate chemical reactions may be added together to form a net reaction. The free-energy change D G for the net reaction is given by the sum of the free-energy changes for the individual reactions. For example, the phosphorylation of glycerol is a necessary step in forming the phospholipids that comprise cell membranes. Recall from the experiment, "Membranes and Proteins: Dialysis, Detergents, and Proton Gradients," that the phospholipids that form cell membranes are formed from glycerol with a phosphate group and two fatty-acid chains attached.

26.11: Oxidative Phosphorylation

This step actually consists of two reactions: 1 the phosphorylation of glycerol, and 2 the dephosphorylation of ATP the free-energy-currency molecule. The reactions may be added as shown in Equationsbelow:. ATP is the most important "free-energy-currency" molecule in living organisms see Figure 2, below. Adenosine triphosphate ATP is a useful free-energy currency because the dephosphorylation reaction is very spontaneous; i.

Thus, the dephosphorylation reaction of ATP to ADP and inorganic phosphate Equation 3 is often coupled with nonspontaneous reactions e. The body's use of ATP as a free-energy currency is a very effective strategy to cause vital nonspontaneous reactions to occur.

The removal of one phosphate group green from ATP requires the breaking of a bond blue and results in a large release of free energy.

Removal of this phosphate group green results in ADP, adenosine diphosphate.


As these coupled reactions e. In a typical cell, an ATP molecule is used within a minute of its formation. During strenuous exercise, the rate of utilization of ATP is even higher.

Hence, the supply of ATP must be regenerated. We consume food to provide energy for the body, but the majority of the energy in food is not in the form of ATP. The body utilizes energy from other nutrients in the diet to produce ATP through oxidation-reduction reactions Figure 3.Oxidative phosphorylation provides most of the ATP that higher animals and plants use to support life and is responsible for setting and maintaining metabolic homeostasis. With increasing energy state, oxygen consumption decreases rapidly until a threshold is reached, above which there is little further decrease.

The ability of oxidative phosphorylation to precisely set and maintain metabolic homeostasis is consistent with it being permissive of, and essential to, development of higher plants and animals.

Life requires continuous input of energy from the environment.

oxidative phosphorylation equation

This energy is needed to carry out the chemical synthesis that maintains metabolism and physical structure of the cells as well as to transport the molecules and ions that establish and maintain the intracellular environment. All of these diverse processes have to be precisely regulated and yet operate at a sustainable energy cost. The energy that can be derived from the environment is limited and there is competition among organisms for that energy supply. The requirements for regulation and energy efficiency in metabolism often conflict: the rates of reactions far displaced from equilibrium irreversible can be precisely controlled but result in loss of large amounts of energy as heat whereas reactions near equilibrium are energy efficient but the rates cannot be used to directly regulate metabolic flux.

Modulation of the rate of irreversible reactions is an effective way to regulate metabolism because any alteration in their rate changes flux through the pathway. Reactions near equilibrium, in contrast, have minimal energy loss and are therefore very efficient but the net flux is small relative to the forward reaction rate.

This limits their regulatory role to the effect of their reactant concentrations on the irreversible reactions. Evolution has selected for: 1 irreversible reactions positioned at the beginning of each pathway in order optimize regulation of the metabolic flux; 2 irreversible reactions following branch points in the pathway in order to optimize distribution of the flux through the branches; 3 near equilibrium reactions within the pathway to minimize energy loss and where the presence of irreversible reactions would destabilize the regulatory system.

At each irreversible step there is a substantial energy loss, but the rest of the reactions are near equilibrium. The three irreversible steps determine the direction and rate of the flux while the near equilibrium reactions allow this to be achieved with a minimal energy cost.

Steps of glycolysis - Cellular respiration - Biology - Khan Academy

The advantage to this design is greatest for metabolic pathways where there is a large flux, such as glycolysis and oxidative phosphorylation. All of the other reactions are freely reversible free energy change near zero and operate either in the forward glycolysis or reverse gluconeogenesis direction as needed. The irreversible steps determine the net forward flux through that part of the pathway and act as valves controlling the direction of the flux, i.

PFK determines whether carbon from glucose is stored as glycogen or metabolized to pyruvate for oxidation by the citric acid cycle CAC or exported as lactate. Metabolic pathways typically involve many different reactions and metabolites. Core hypotheses, those which are considered most important, strongly influence the interpretation given to sets of experimental data. Relevance of the Lakatosian Research Programme to the study of metabolism is readily observed in the literature. Many of these limitations can be overcome by building a computational model.

Properly designed computational models involve: 1 listing all of the metabolites and metabolic transitions considered to be responsible for the regulating flux and; 2 writing equations that explicitly quantify the contributions of each to the whole.In oxidative phosphorylation the oxidation of catabolic intermediates by molecular oxygen occurs via a highly ordered series of substances that act as hydrogen and electron carriers.

They constitute the electron transfer system, or respiratory chain. In most animals, plants, and fungi, the electron transfer system is…. The electrons are then passed from one electron carrier to another by means of an electron-transport chain. Each electron carrier in the chain has an increasing affinity for electrons, with the…. In the oxidative phosphorylation stage, each pair of hydrogen atoms removed from NADH and FADH 2 provides a pair of electrons that—through the action of a series of iron-containing hemoproteins, the cytochromes—eventually reduces one atom of oxygen to form water.

In it was discovered that the. Granules in the sarcoplasm of muscle cells contain glycogen, the storage form of carbohydrate. The breakdown of glycogen and the metabolism of the individual units of the resulting carbohydrate through glycolysis, the Krebs cycle, and oxidative phosphorylation are important sources of ATP, the…. All the participating enzymes are located inside the mitochondrial inner membrane—except one, which is trapped in the space between the inner and outer membranes.

The process by which green plants convert light energy to chemical energy is called photophosphorylation see photosynthesis.

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Oxidative phosphorylation. Oxidative phosphorylation chemical reaction. Alternative Title: respiratory-chain phosphorylation. Learn about this topic in these articles: major reference.Why don't fictional characters say "goodbye" when they hang up a phone? All Rights Reserved. The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Multiply.

Hottest Questions. Previously Viewed. Unanswered Questions. What is the equation for oxidative phosphorylation? Wiki User Related Questions Asked in Genetics, Biochemistry, The Difference Between What is the difference between oxidative and substrate level phosphorylation?

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Unlike oxidative phosphorylation, in substrate level phosphorylation the oxidation and phosphorylation are not coupled. Asked in English Language, Genetics, Biochemistry What is oxidative phosphorylation and substrate level phosphorylation? See related questions, "What is oxidative phosphorylation" and "What is substrate-level phosphorylation" below for individual explanations.

Asked in Biology What is oxidative phosphorylation and what is its purpose? Oxidative phosphorylation is a process in which most ATPs are produced in cellular respiration. Asked in Genetics What type of phosphorylation does not require a membrane?

Asked in Science, Biology, Genetics Where does the oxidative phosphorylation occur in the cell? Asked in Photosynthesis What are the two types of phosphorylation that occur during photosynthesis? Substrate-level phosphorylation and oxidative phosphorylation. Asked in Biology In fermentation is ATP produced by substrate level phosphorylation or oxidative phosphorylation or both or neither?

ATP is produced by substrate level phosphorylation during glycolisis.

oxidative phosphorylation equation

There is no oxidative phosphorylation in fermentation since it's an anaeorobic respiration. Asked in Microbiology, Photosynthesis Photophosphorylation is most similar to?In most eukaryotesthis takes place inside mitochondria. Almost all aerobic organisms carry out oxidative phosphorylation. This pathway is so pervasive because the energy of the double bond of oxygen is so much higher than the energy of the double bond in carbon dioxide or in pairs of single bonds in organic molecules [3] observed in alternative fermentation processes such as anaerobic glycolysis.

During oxidative phosphorylation, electrons are transferred from electron donors to electron acceptors such as oxygen in redox reactions. These redox reactions release the energy stored in the relatively weak double bond of O 2which is used to form ATP. In eukaryotesthese redox reactions are catalyzed by a series of protein complexes within the inner membrane of the cell's mitochondria, whereas, in prokaryotesthese proteins are located in the cell's intermembrane space.

These linked sets of proteins are called electron transport chains. In eukaryotes, five main protein complexes are involved, whereas in prokaryotes many different enzymes are present, using a variety of electron donors and acceptors. The energy transferred by electrons flowing through this electron transport chain is used to transport protons across the inner mitochondrial membranein a process called electron transport.

This generates potential energy in the form of a pH gradient and an electrical potential across this membrane. This store of energy is tapped when protons flow back across the membrane and down the potential energy gradient, through a large enzyme called ATP synthase ; this process is known as chemiosmosis. The ATP synthase uses the energy to transform adenosine diphosphate ADP into adenosine triphosphate, in a phosphorylation reaction. The reaction is driven by the proton flow, which forces the rotation of a part of the enzyme; the ATP synthase is a rotary mechanical motor.

Although oxidative phosphorylation is a vital part of metabolism, it produces reactive oxygen species such as superoxide and hydrogen peroxidewhich lead to propagation of free radicalsdamaging cells and contributing to disease and, possibly, aging senescence.

oxidative phosphorylation equation

The enzymes carrying out this metabolic pathway are also the target of many drugs and poisons that inhibit their activities. It is the terminal process of cellular respiration in eukaryotes and accounts for high ATP yield.

Oxidative phosphorylation works by using energy -releasing chemical reactions to drive energy-requiring reactions: The two sets of reactions are said to be coupled. This means one cannot occur without the other. Both the electron transport chain and the ATP synthase are embedded in a membrane, and energy is transferred from the electron transport chain to the ATP synthase by movements of protons across this membrane, in a process called chemiosmosis.

The movement of protons creates an electrochemical gradient across the membrane, which is often called the proton-motive force. ATP synthase releases this stored energy by completing the circuit and allowing protons to flow down the electrochemical gradient, back to the N-side of the membrane.

The two components of the proton-motive force are thermodynamically equivalent: In mitochondria, the largest part of energy is provided by the potential; in alkaliphile bacteria the electrical energy even has to compensate for a counteracting inverse pH difference.

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However, they also require a small membrane potential for the kinetics of ATP synthesis. In the case of the fusobacterium Propionigenium modestum it drives the counter-rotation of subunits a and c of the F O motor of ATP synthase.

The amount of energy released by oxidative phosphorylation is high, compared with the amount produced by anaerobic fermentationdue to the high energy of O 2.

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These ATP yields are theoretical maximum values; in practice, some protons leak across the membrane, lowering the yield of ATP. The electron transport chain carries both protons and electrons, passing electrons from donors to acceptors, and transporting protons across a membrane. These processes use both soluble and protein-bound transfer molecules. In mitochondria, electrons are transferred within the intermembrane space by the water- soluble electron transfer protein cytochrome c.

Cytochrome c is also found in some bacteria, where it is located within the periplasmic space. Within the inner mitochondrial membrane, the lipid -soluble electron carrier coenzyme Q10 Q carries both electrons and protons by a redox cycle. When Q accepts two electrons and two protons, it becomes reduced to the ubiquinol form QH 2 ; when QH 2 releases two electrons and two protons, it becomes oxidized back to the ubiquinone Q form.

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As a result, if two enzymes are arranged so that Q is reduced on one side of the membrane and QH 2 oxidized on the other, ubiquinone will couple these reactions and shuttle protons across the membrane. Within proteins, electrons are transferred between flavin cofactors, [6] [14] iron—sulfur clusters, and cytochromes. There are several types of iron—sulfur cluster. The simplest kind found in the electron transfer chain consists of two iron atoms joined by two atoms of inorganic sulfur ; these are called [2Fe—2S] clusters.

The second kind, called [4Fe—4S], contains a cube of four iron atoms and four sulfur atoms. Each iron atom in these clusters is coordinated by an additional amino acidusually by the sulfur atom of cysteine.People commonly refer to the act of breathing as respiration.

More correctly respiration is a process that occurs within cells. Respiration converts the energy of glucose and other molecules into cellular energy. Cells are then able to use this energy to perform functions such as build proteinsreplicate DNA and breakdown wastes. Respiration is a series of chemical reactions. The series of reactions gradually releases the energy of molecules such as glucose.

The released energy is transferred to molecules such as ATP and used to power activity within cells. Cellular respiration can be both aerobic or anaerobic.

oxidative phosphorylation equation

Aerobic respiration uses oxygen and is the most common and most efficient method of respiration. The overall equation of aerobic respiration can be summed up as:. Anaerobic respiration replaces the oxygen in aerobic respiration with other molecules.

The products of anaerobic respiration are compounds such as methane or lactic acid rather than carbon dioxide and water. The process of respiration occurs in the mitochondria and cytoplasm of eukaryotic cells.

In prokaryotic cells respiration occurs in the cytoplasm and across the plasma membrane. The whole process of respiration can be split into three stages: glycolysis, the citric acid cycle and oxidative phosphorylation. Glycolysis is the splitting of glucose into two molecules of pyruvate. The process includes a total of nine reactions that all occur in the cytoplasm in both eukaryotic and prokaryotic cells.

Energy is both invested and paid back in separate phases of glycolysis. All up a total of two molecules of ATP are produced through glycolysis for every glucose molecule that is converted into pyruvate.

Glucose is a sugar that contains six carbon atoms. During glycolysis, glucose is split into two molecules of pyruvate which is a three carbon molecule. A glucose molecule has a ring of carbon atoms. The first four reactions of the glycolysis pathway breakdown the ring of the glucose molecule in two molecules of G3P glyceralderhydephosphate. Splitting the ring of atoms requires the investment of energy and uses two molecules of ATP.

The last five reactions of glycolysis converts G3P into pyruvate. The glycolysis pathway therefore uses two molecules of ATP but produces four, giving a net increase of two molecules of ATP. In prokaryotes the remaining steps of respiration are performed in the cytoplasm and the plasma membrane. The citric acid cycle, also known as the Krebs cycle, is the second phase of cellular respiration. Through the citric acid cycle acetyl CoA is broken down to carbon dioxide.

The citric acid cycle is a series of eight reactions. The following seven reactions lead to the release of two molecules of carbon dioxide. These two different molecules are used to carry electrons from the citric acid cycle to the electron transport chain. Oxidative phosphorylation is by far the most productive stage of respiration. Far more usable cellular energy is produced during oxidative phosphorylation than during glycolysis and the citric acid cycle combined.

The electron transport chain is a chain of molecules that electrons are passed along. It utilizes electrons made available during glycolysis and the citric acid cycle. The electrons are donated to the electron transport chain and passed along the chain of molecules.The electron transport chain uses the electrons from electron carriers to create a chemical gradient that can be used to power oxidative phosphorylation.

Oxidative phosphorylation is a highly efficient method of producing large amounts of ATP, the basic unit of energy for metabolic processes. During this process electrons are exchanged between molecules, which creates a chemical gradient that allows for the production of ATP.

The most vital part of this process is the electron transport chain, which produces more ATP than any other part of cellular respiration. The electron transport chain is the final component of aerobic respiration and is the only part of glucose metabolism that uses atmospheric oxygen. Electron transport is a series of redox reactions that resemble a relay race.

Electrons are passed rapidly from one component to the next to the endpoint of the chain, where the electrons reduce molecular oxygen, producing water.

This requirement for oxygen in the final stages of the chain can be seen in the overall equation for cellular respiration, which requires both glucose and oxygen. A complex is a structure consisting of a central atom, molecule, or protein weakly connected to surrounding atoms, molecules, or proteins. The electron transport chain is an aggregation of four of these complexes labeled I through IVtogether with associated mobile electron carriers.

The electron transport chain is present in multiple copies in the inner mitochondrial membrane of eukaryotes and the plasma membrane of prokaryotes. The electron transport chain : The electron transport chain is a series of electron transporters embedded in the inner mitochondrial membrane that shuttles electrons from NADH and FADH 2 to molecular oxygen.

In the process, protons are pumped from the mitochondrial matrix to the intermembrane space, and oxygen is reduced to form water. To start, two electrons are carried to the first complex aboard NADH. A prosthetic group is a non-protein molecule required for the activity of a protein. Prosthetic groups can be organic or inorganic and are non-peptide molecules bound to a protein that facilitate its function.

Prosthetic groups include co-enzymes, which are the prosthetic groups of enzymes. Complex I can pump four hydrogen ions across the membrane from the matrix into the intermembrane space; it is in this way that the hydrogen ion gradient is established and maintained between the two compartments separated by the inner mitochondrial membrane.

The compound connecting the first and second complexes to the third is ubiquinone Q. The Q molecule is lipid soluble and freely moves through the hydrophobic core of the membrane. Once it is reduced to QH 2ubiquinone delivers its electrons to the next complex in the electron transport chain. This enzyme and FADH 2 form a small complex that delivers electrons directly to the electron transport chain, bypassing the first complex.

Since these electrons bypass, and thus do not energize, the proton pump in the first complex, fewer ATP molecules are made from the FADH 2 electrons.

Mitochondrial Functions and Biological Oxidations

The number of ATP molecules ultimately obtained is directly proportional to the number of protons pumped across the inner mitochondrial membrane. The third complex is composed of cytochrome b, another Fe-S protein, Rieske center 2Fe-2S centerand cytochrome c proteins; this complex is also called cytochrome oxidoreductase. Cytochrome proteins have a prosthetic heme group. The heme molecule is similar to the heme in hemoglobin, but it carries electrons, not oxygen.

The heme molecules in the cytochromes have slightly different characteristics due to the effects of the different proteins binding them, which makes each complex. Complex III pumps protons through the membrane and passes its electrons to cytochrome c for transport to the fourth complex of proteins and enzymes. Cytochrome c is the acceptor of electrons from Q; however, whereas Q carries pairs of electrons, cytochrome c can accept only one at a time.

The fourth complex is composed of cytochrome proteins c, a, and a 3. This complex contains two heme groups one in each of the cytochromes a and a 3 and three copper ions a pair of Cu A and one Cu B in cytochrome a 3. The cytochromes hold an oxygen molecule very tightly between the iron and copper ions until the oxygen is completely reduced.

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