# Chemolithotrophs --- **Chemolithotrophs** are a [[metabolism#Classifications|class of organism]] that uses inorganic molecules as their electron source. Here we will look specifically at how *anaerobic* chemolithotrophs may differ from their *aerobic [[metabolism#Chart|chemoorganotroph]]* cousins. ## ATP Throughput **Chemolithotrophic anaerobes** produce less ATP per molecule electron donor than it's chemoorganotrophic aerobe cousins. For example, if we look at glucose and O$_2$, there is a huge difference in the strength of the molecule's [[electronegativity]]. There can be many more in-between steps to harvest power from [[redox.png|redox]] reactions in the span between A and B. It can generate more pull. ![[electron source and acceptor electronegativity.png]] In the above chart we can see that glucose is quite high on the left-hand side of the screen, and O$_2$ is quite low on the right-hand side of the screen. There is a lot of juice that can be squeezed out of that difference. Chemolithotrophic anaerobes on the other hand might use something like Fe$^{2+}$ as an electron source, and NO$_3^-$ as an electron acceptor. There can be *some pull* that can be derived from this distance, but not nearly as much. ## Middlemen Electron Carriers **Chemolithotrophic anaerobes** may not use [[NAD|NAD+]] or [[FAD#FADH|FADH]] as [[electron carrier|electron carriers]] between different reactions because it ends up being *less* electronegative than the electron source itself, which is counterproductive. The middleman has to be somewhere in between the source and the acceptor in order to function. In the case that NAD+ or FADH does not work, these cells can actually use [[coenzyme Q]] or [[ETC (mitochondria)|cytochrome c]] that detaches from the membrane to float over and grab an electron. ## ETC Composition The [[ETC (bacterial)|ETC]] of **chemolithotrophic anaerobes** can be different from chemoorganotrophic aerobes in that it lacks complex III, and thus use [[ETC (bacterial)|menaquinone]] as the electron carrier to complex IV. ___