Lecture 37Outline of Last Lecture I. Mitochondrial Electron Transport ChainII. Complex IIII. Complex IIA. Coenzyme QIV. Complex IIIV. Complex IVA. Oxidative PhosphorylationB. ATP Production Outline of Current Lecture I. Oxidative Phosphorylation InhibitionII. Hibernation A. 2,4-DinitrophenolIII. Heterotrophs vs. PhototrophsCurrent Lecture This lecture starts out by finishing the information on oxidative phosphorylation. Some compounds canblock different parts of the mitochondrial electron transport chain from working. Usually these compounds areextremely toxic. When one thing is blocked in the electron transport chain, everything upstream will eventuallybecome blocked as well. This is due to that point already being reduced. The other electrons can’t be passed on until that point is oxidized. Eventually, this will lead to NAD+ regeneration being stopped. This will stop the TCA cycle from being able to continue. Complex I can be inhibited by rotenone. Complex III can be inhibited by antimycin A. Complex IV can be inhibited by cyanide, azide, and carbon monoxide. The oxidative phosphorylation process is linked to hibernation. Hibernating animals use brown fat to oxidize large amounts of fatty acids. This process generates heat. Brown fat is brown in color due to the large number of mitochondria and therefore large amount of cytochromes present. This process also uncouples the electron transport chain from ATP synthesis. This is done through an uncoupling protein called thermogenin. The heat formed through this comes from the energy that would have been used to make ATP. There are other chemicals that can uncouple this proton gradient from the synthesis of ATP. An exampleof this is 2,4-dinitrophenol. It is a hydrophobic low molecular weight substance. This molecule can diffuse through the mitochondrial inner membrane. It shuttles protons across this membrane and dissipates the proton gradient. This molecule, although very toxic, was marketed in the past as a weight loss drug. Now we will move onto a new chapter about photosynthesis. Heterotrophs ingest plants and animals. They oxidize organic compounds to create ATP. Phototrophs are the other type. They absorb solar radiation and divert the energy through electron chains. This not only creates ATP but also reducing power in the form BCHM 307 1nd Editionof NADPH. Scientists throughout the centuries discovered that oxygen was produced in photosynthesis. They also discovered that sunlight is required for
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