Kevin Ahern's BB 350 (Electron Transport/Oxidative Phoshorylation) 2014 – #31May 24, 2021 Off By editorialteam
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Highlights Electron Transport/Oxidative Phosphorylation
1. Electron transport (ETS) occurs in the inner membrane of the mitochondrion.
2. In ETS, electrons from NADH move to complex I and from FADH2, they move into complex II. Losing electrons like this converts them to NAD+ and FAD.
3. Electrons move through the complexes as follows
Complex I – Coenzyme Q – Complex III – Cytochrome C – Complex IV – Oxygen. When oxygen gains electrons, it creates water.
4. Electrons from complex II are passed to Coenzyme II and then they take the same pathway.
5. As electrons flow through complexes I, III, and IV, protons are “pumped” out of the mitochondrion. This ‘charges’ the battery.
6. Note that electrons starting with NADH pump more protons that electrons starting with Complex II. This ultimately (in oxidative phosphorylation) results in production of more ATPs per NADH than per FADH2.
7. Coenzyme Q acts as a “traffic cop”, accepting electrons in pairs and passing them on individually.
8. A compound called 2,4 DNP (2,4 dinitrophenol) was used as a “miracle” diet drug about a century ago with disastrous consequences. It acted to poke a hole in the mitochondrial inner membrane, allowing protons to leak back into the matrix without passing through complex V. As a result, when 2,4 DNP is present, electrons move through the electron transport system, but NO ATP is made. Consequently, cells burn everything they can to try to make ATP, but they can’t. Oxygen consumption goes way up and the body temperature goes way up, but no ATP is made by oxidative phosphorylation. Death was a frequent result of 2,4DNP use.
9. Note that electrons starting with NADH pump more protons that electrons starting with Complex II. This ultimately (in oxidative phosphorylation) results in production of more ATPs per NADH than per FADH2.
10. Certain compounds inhibit the movement of electrons through the electron transport system. They include inihibitors of the movement of electrons through Complex I (rotenone and amytal), Complex III (Antimycin A), and Complex IV (cyanide, carbon monoxide,azide).
11. Oxidative phosphorylation occurs when protons move BACK into the mitochondrion (after being pumped out) through a complex commonly called Complex V. Complex V has the mushroom-like shape, as shown in class. This complex ROTATEs as protons pass through it. Rotation of the complex creates ATP.
12. Complex V has three sets of subunits in the F1 domain that make the ATP. They do this by flipping between states labeled L, T, and O. Flipping is controlled by the ‘rotor’ described in class that is attached to the rotating F0 subunit. Rotation is caused by movement of protons through the complex. L is the state that binds ADP and Pi. T is the state that compresses them together to make ATP. O is the state that releases the ATP.