let's round out our conversation about the electron transport system and fermentation by mentioning that some bacteria can make more than one product from from fermentation so these would be heterofermentative organisms an organism that just makes one product is homo fermentative there are a wide variety too of fermentation products that bacteria can make and some of them smell terrible so that's why occasionally a fermenting organism is very very unpleasant to smell things like butyric acid are very very smelly um but you know bacteria can make things like acetone which you find in nail polish remover they can make isopropyl alcohol which can be used as a antiseptic on skin all sorts of different molecules are made as a result of fermentation by bacteria if you've taken more than one biology class i bet you you've learned about the glycolysis the krebs cycle the electron transport chain in more than one of them and you may be wondering right now why we teach this in just about every class and the reason is is because these pathways are completely central to metabolism as it occurs in cells so the arrows that you see here are going one way because they're showing catabolism but actually they go both ways so cells can take molecules like glucose they can break them down to pyruvate and they can then turn those into amino acids acetyl coa as well as some of the krebs cycle intermediates are also convertible to different amino acids that your body needs to build proteins other molecules like glyceraldehyde 3-phosphate can get converted to glycerol and help your body build lipids acetyl coa is critical in the synthesis of fatty acids and then if you're breaking down fats these molecules would then go back into glycolysis and the krebs cycle so this is a really efficient mechanism if you think about it it means that your body doesn't on your cells don't have to build separate pathways for absolutely everything they do you have this big central pathway that many many different processes in the cell take advantage of um on this slide we're just showing the breakdown of fats which is really shown over here but it's going through just the process of taking a lipid a triglyceride and breaking it down into glyceride and glycerol and fatty acids and undergoing a process called beta oxidation and this is a really efficient way for your body to break down fats and get lots of energy very quickly because acetyl coa gets shuttled right into the krebs cycle and you know from studying this now that from acetyl coa on is where the vast majority of the atp gets made evil cell biology teachers love to show students pictures like this because it's terrifying right the level of complexity and this is actually a simple bacterial cell and it's not even showing all of the different biochemical reactions that occur in the cell but i do want to point out that front and center is glycolysis and the krebs cycle and the electron transport chain components are embedded into the lipid bilayer i don't know that they're actually shown in this particular diagram but the point here is just to show the interrelatedness between these molecules that are part of these uh pathways glycolysis and krebs and show how they they interact with other pathways in the cell so you know there are some pathways that exist somewhat independently but a lot of them are tied in through different intermediates to glycolysis and krebs cycle so just memorize this for the test i'm just kidding just a silly joke you don't need to memorize this i hope it just gives you an appreciation for the complexity of the biochemistry of cells that's it for our study of microbial metabolism the next step is to review and take our next exam so good luck please let me know if you have questions