# Bacterial Electron Transport Chains As [[bacteria]] do not have any mitochondria or chloroplast in which to put their ETCs, they have to do it slightly differently. Although the overall system works along the same lines as the [[ETC (mitochondria)|mitochondrial ETCs]], there are also significant differencses. A really important factor in determining these differences is the differences in the resources that a bacteria might use, and consequently differences in the make up of their ETC. ## Variables ### Complex IV Recall that [[ETC (mitochondria)#Complex IV|complex IV]] in the mitochondrial ETC is the complex that recieves it's electron from [[ETC (mitochondria)|cytochrome c]] and passes it off to the final electron acceptor. #### Shape Complex IV *always* is the one that passes its electron to the final electron acceptor, but that can [[metabolism#names|varry wildely]] as to what it actually is. Due to this, the shape of the complex itself changes to accomidate it. #### Anaerobic Respirators The molecule that brings the electron over to complex IV in anaerobic respirators is called **[[vitamin K|menaquinone]]**. #### Strength Complex IVs also vary in how strongly it attracts the final electron acceptor. For example, bacteria in oxygen poor environments benefit from a complex IV with a strong pull towards O$_2$, but bacteria in an oxygen rich environment might want to limit the amount of O$_2$ it lets into the system, and have a complex IV with a weak pull towards oxygen. For some reason, these types of weak-pull ETCs pump more protons. ### Complex III & Cytochrome c Some bacteria completely lack [[ETC (mitochondria)#Complex III|complex III]] or [[ETC (mitochondria)#Cytochrome c|cytochrome c]]. Instead [[coenzyme Q]] delivers the electron to complex IV, in this case sometimes called "ubiquinol oxidase". ### Complex I There are two main classes of [[ETC (mitochondria)#Complex I|complex I's]]: those that pump protons and those that do not. They either serve as pumps or not depending on the electron source that binds with them. ### The Coenzyme In aerobic respirators, the coenzime that ferries electrons around the ETC is [[coenzyme Q]], but that is not compatible with anaerobic respirators, so they instead use menaquinone (menQ). ## Cases ### *Pseudomonas* The ETC of the bacteria *Pseudomonas* is pretty much identical to the type found in animal's mitochondria, but it is located in the [[plasma membrane]] instead. It's complex IV is cytochrome oxidase ### *E. coli* The ETC of the bacteria *[[Escherichia coli|E. coli]]* is distinct because it doesn't have [[ETC (mitochondria)#Complex III|complex III]] or [[ETC (mitochondria)#Cytochrome c|cytochrome c]]. Because of this gap, [[coenzyme Q]] brings the electron straight to [[ETC (mitochondria)#Complex IV|complex IV]]. This is thus called *ubiquinol oxidase*. ___