Oxidative Phosphorylation
Process
THE
Oxidative phosphorylation is actually the last part of a 3 step process called cellular respiration. The first two steps are glycolysis and Krebs cycle (or citric acid cycle), which generates some ATP while also making the products necessary to begin the final step.
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Oxidative phosphorylation itself is also a multi-step process. It is composed of an electron transport chain, which are the protein complexes attached to the cristae, and chemiosmosis, which will be explained below. Let’s begin learning!
1. The electron carriers NADH and FADH2 made during Krebs Cycle go through two different protein complexes attached to the cristae, and become NAD+ and FAD. Specifically, 3 NADH molecules goes to the first protein complex and 3 FADH2 molecules go through protein complex 2. This also means that the molecules go through an oxidation process, or lose electrons.
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2. The electron carrier NADH also create a "proton gradient" in protein complex I by moving H+ ions from the matrix of the mitochondria to the intermembrane space.
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3. A compound known as UQH2 (ubiquinone) carries electrons to protein complex 3. This also causes more H+ ions to be pumped out of the electron transport chain.
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4. A product of the third protein complex named cytochrome C brings electrons to the 4th protein complex. Oxygen (02) towards the end of the electron transport chain splits to be able to combine with the H+ ions that are found in the matrix and produce water as a byproduct.
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45 Chemiosmosis (the process of ions moving down their gradient) occurs when the H+ ions move down their proton gradient and go through the ATP synthase protein complex. The protein complex spins, which makes the H+ ions combine with ADP (adenosine diphosphate) and inorganic phosphate (Pi) to make ATP!
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5. Oxidative phosphorylation produces the most ATP out of cellular respiration. It makes 34 ATP molecules!
