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    Hi everyone.
    i am doing A levels, please could anyone please explain oxidative phosphorylation under energy and respiration. i have read it a lot of times but the AS and A2 textbook i was given in my school didn't explain it well. I appreciate any answer
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    During my A2 in biology, the word was non-cyclic oxidativephotophosphorylation. non-cyclic part was obvious, oxidative- oxygen(this im not 100%sure about) photo-light, phos- phosphate molecule, phosphorylation-synthesis. This was a part of photosynthesis, so im not sure about respiration, but maybe you could work it out?
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    I'm well gladd I got full UMS in this unit...forgotten everything about Biology now! It'd be a pain to re-sit!
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    Two words I'm so glad i've forgotten the definition of after A-level. From memory, it's something to do with how oxygen is used in the metabolic pathway of animals to make energy.

    Don't expect anymore detail from me without a quick visit to Google :P
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    Oxidative phosphorylation is basically the last stage of respiration where most of the ATP is produced out of the 4 main metabolic pathways and uses up all the reduced NAD and FAD produced by the other 3 pathways (glycolysis, link reaction and krebs cycle).

    Firstly, this process occurs across the inner mitochondrial membrane between the matrix and intermembrane space of the mitochondrion. The membrane consists of many electron carries (proteins) and ATP synthase enzymes. Reduced NAD becomes reoxidised and donates its 2 electrons and protons to the first electron carrier. The electron are then transported through the membrane to one electron carrier to the next. After each 'jump' an electron makes it releases a certain amount of energy as it goes from a higher energy level to a slightly lower one each 'jump'. The main purpose of this is to use the energy to pump the protons using coenzymes bound to the electron carries across the membrane into the intermembrane space. As the membrane is impermeable to protons, a pH/proton/electrochemical gradient builds up with a higher concentration in the intermembrane with a lower one in the matrix. The only way for protons to move down their gradient into the matrix are through proton channels bound to the ATP synthase enzymes. This proton flow through ATP synthase is known as chemiosmosis and the force of this flow produces energy. This energy rotates an axel round and round joining ADP to Pi to produce ATP.

    Reduced FAD is physically bound to the 2nd of the 5 electron carries and also becomes reoxidised and again donates its 2 electrons and protons. However, the protons are unable to be pumped across the membrane unlike the ones coming from reduced NAD and instead travel directly to the last electron carrier separate from the membrane in the matrix, molecular oxygen. Its 2 electrons travel as normal as part of the electron transport chain.

    So, the 2 protons from reduced FAD, 2 protons from chemiosmosis and 4 electron from the electron transport as well as oxygen reacts to form water. Essentially, this is just reacting 2 hydrogen atoms, or one molecule of hydrogen, with one molecule of oxygen. Therefore oxygen is reduced to water as its gaining electrons.

    Hope this helped!
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    Oxidative phosphorylation is the process whereby a substance gains a phosphate group - in this case ADP to form ATP - using the energy from the oxidation of another substance. Oxidation, remember, is the loss of electrons. In the electron transport chain of respiration, electrons pass onto one of the carrier molecules, reducing it, and then pass onto the following carrier molecule. This oxidises the former carrier molecule since it has lost electrons. This process allows a phosphate group to bind with ADP. We say that the carrier molecules are performing oxidative phosphorylation - they are themselves oxidised, in turn phosphorylating another molecule (ADP).
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    Oxidative phosphorylation describes one of the two ways of producing ATP from ADP (the other being substrate level phosphorylation where an inorganic phosphate is directly joined to an ADP molecule; we see this is the energy conservation stage of glycolysis where 4ATPs are produced giving a net 2ATP). It is carried out in the electron transport chain (ETC) which is located on the cristal membrane of the inner membrane of the mitochondria. Through a series of membrane bound redox reactions, ATP is synthesised from ATP. Carriers such as NADH and FADH2 are oxidised and pass on electrons to a series of proteins embedded in the cristae. The electrons hop from carrier to carrier; as they do, previous protein complexes are oxidised and hydrogen ions are pumped into the inter-membrane space. Electrons are finally accepted by oxygen and it is reduced to water. The build-up of H+ ions (or oxonium H3O+ ions to be more accurate) in the inner membrane causes a concentration gradient to build up across the inner membrane. The H3O+ ions flow down this concentration gradient through a protein complex called ATP synthase (or ATP synthetase). The movement of H3O+ ions - much like water through a turbine - drives the ATP synthase. Here ADP is phosphorylated (ADP + Pi --> ATP) and ATP is produced. Since the ETC involved a series of redox reactions with protein carriers and cofactors being oxidised, it is known as oxidative phosphorylation.

    I hope that helped you!
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    thank you, you have really helped me.But please can you explain the difference substrate level phosphorylation and chemiosmosis.
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    (Original post by l4ith)
    Oxidative phosphorylation describes one of the two ways of producing ATP from ADP (the other being substrate level phosphorylation where an inorganic phosphate is directly joined to an ADP molecule; we see this is the energy conservation stage of glycolysis where 4ATPs are produced giving a net 2ATP). It is carried out in the electron transport chain (ETC) which is located on the cristal membrane of the inner membrane of the mitochondria. Through a series of membrane bound redox reactions, ATP is synthesised from ATP. Carriers such as NADH and FADH2 are oxidised and pass on electrons to a series of proteins embedded in the cristae. The electrons hop from carrier to carrier; as they do, previous protein complexes are oxidised and hydrogen ions are pumped into the inter-membrane space. Electrons are finally accepted by oxygen and it is reduced to water. The build-up of H+ ions (or oxonium H3O+ ions to be more accurate) in the inner membrane causes a concentration gradient to build up across the inner membrane. The H3O+ ions flow down this concentration gradient through a protein complex called ATP synthase (or ATP synthetase). The movement of H3O+ ions - much like water through a turbine - drives the ATP synthase. Here ADP is phosphorylated (ADP + Pi --> ATP) and ATP is produced. Since the ETC involved a series of redox reactions with protein carriers and cofactors being oxidised, it is known as oxidative phosphorylation.

    I hope that helped you!
    Thanks a lot you have really helped me and now i understant oxidative phosphorylation
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    (Original post by porkstein)
    Oxidative phosphorylation is the process whereby a substance gains a phosphate group - in this case ADP to form ATP - using the energy from the oxidation of another substance. Oxidation, remember, is the loss of electrons. In the electron transport chain of respiration, electrons pass onto one of the carrier molecules, reducing it, and then pass onto the following carrier molecule. This oxidises the former carrier molecule since it has lost electrons. This process allows a phosphate group to bind with ADP. We say that the carrier molecules are performing oxidative phosphorylation - they are themselves oxidised, in turn phosphorylating another molecule (ADP).
    Thanks a lot, you have really helped me. have a happy xmas eve
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    (Original post by adedolapo)
    thank you, you have really helped me.But please can you explain the difference substrate level phosphorylation and chemiosmosis.
    Substrate level phosphorylation is when you remove a phosphate from a substrate (phosphate containing compound) and directly attach it to a molecule of ADP which is how ATP is made during glycolysis and krebs cycle. No ATP is made in the link reaction. I'm sure there is more to it than this however I don' t think you'd need anything more than that at A-Level.

    Chemiosmosis is basically just the same with ordinary osmosis however in this case it involves protons or hydrogen ions moving down the concentration gradient from a higher area of concentration to a lower one which is what most substances naturally do. During oxidative phosphorylation however, protons move by chemiosmosis through the proton/ion channels that ATP synthase containing giving the energy to join ADP and Pi at a fast rate.
 
 
 
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