now sometimes organisms need to get energy a different way they need to get it through a process because maybe they don't have any oxygen available what was the function of the oxygen remember we talked about it excuse me being the final electron acceptor in the oxidative phosphorylation portion of chemiosmosis well if you don't have oxygen you're not going to get the etc functioning so you're not going to get the gradient so what happens for those organisms that do this when there's no oxygen well they do fermentation when you say oxygen people will call that air aerobic when there is id more oxygen when there is an absence of oxygen that is called anaerobic without oxygen this is an important word here anaerobic versus aerobic there's two kinds of fermentation that can happen so this should look pretty familiar to you it should look like something we've just talked about what does it look like hopefully it looks like glycolysis to you because we're starting with glucose ending up with two pyruvate and we're getting some nadh and a little bit of atp and all things are good if this could continue on but remember in this situation there's no oxygen or too little of it so we might be going through this process but we can't continue on to the second half what's an organism to do well you've got to pyruvate here and well stepping back here if you wanted to do this again and the idea is to make more atp that's what we want right you're going to need a few things you're going to need glucose you're going to need adp and you're going to need nadh or sorry nad plus now in order to go to atp getting adp is not a problem just use this up and then you'll have plenty to go forward again so this one's not a problem we can get adp glucose if there's plenty of food around you also not a problem just eat more it's this that's a little bit challenging how are you going to get this again so what we'll do is we'll start off with what we have here and we'll move forward what we need to do is go through to get nad plus again well we have nadh all we have to do is get to nad plus what is nad plus well remember if this right here has electrons and this one doesn't that means we've lost it all we've done here is go through an oxidation if you go through the oxidation then you're ready to get nad plus so you just go through an oxidation right of nadh now you've got nad plus again so now we have all three available to do that though to get an oxidation something had to gain electrons and it was this pyruvate did to become lactate now this kind of fermentation is called lactic acid fermentation and you're probably familiar with this if you go say running really hard or working out at the gym and you didn't get quite enough to breathe in like you're running really hard then you can get that lactic acid sore muscle pain well it doesn't sound ideal you've got sore muscles but if you think about it it does have a good evolutionary reason for this to happen first of all imagine that you are for example on safari in africa and you have decided to go out into the savannah where the grasslands are to see the giraffes and the and the lions but unfortunately your safari truck has now broken down it has it's not capable of running right now and it has no top to it so you're not very safe from the lions so what are you gonna do they're getting hungry you run you run as much as you can maybe you can get up that tree hopefully but in the process of doing so you've been running so hard that ow now your muscles really hurt but you know what it's okay because the lion's lost interest they're going after that gazelle anyway so you survived it was worth it so what do you do after that hard run you lean over and when you have been running you didn't get enough oxygen in but now that you can take a moment and catch your breath you get enough oxygen so that way we can continue on break down this lactic acid and move on into regular cellular respiration and then your muscles that are sore won't be a sore and again it was worth it you survived the lions got a great story so you have sore muscles here there are also organisms that kind of live this lifestyle all the time i mean we have mitochondria we live with oxygen but bacillus bacteria they're a prokaryote you know that those don't have membrane-bound organelles so they are going to have to go through this process whenever they don't have oxygen readily available to them and we happen to use it because it makes things really lovely for cheeses and yogurts and so forth like that because they have a nice acid in there lactic acid so lactic acid fermentation is really beneficial in a situation where you don't have oxygen so again the idea fermentation is going to happen when there's no oxygen what do we call that again anaerobic okay so um and the idea of it is really so we can get enough nad plus again so we can go through this process so we can have enough atp all right so that's lactic acid fermentation when you take a look here this is going to look mighty familiar too let me clear all this here so here again starting off with glycolysis and what we need to do again is make more atp so that's our goal is to get atp so that's what we need well to get that we're gonna all we need to do is get this so if we break this down we've got our adp for glucose eat some more how is it we're gonna get our nad plus well you know we could take nadh which currently has electrons in it and if we lose those electrons right then we'll have nad plus again so that's what's going to happen we're going to go through and we're going to make nadh into nad plus so again the process that we're going through here is an oxidation of nadh oops h all right and that works out great but then where's the reduction well you know the reduction has to be the other part of it so it's the reduction of pyruvate into something else now this happens with different organisms so the process is a little bit different we're not making lactic acid we're going to make ethanol this time which is really nice because guess what we get a little bit of co2 there too and when we get the co2 that's going to have a nice little effect that little effect is in this way so maybe we can use it to make bread if you don't use fermentation with your yeast then you get a cracker but once there the yeast are in the center of that dough and they're not getting access to oxygen because they're really just mixed in there they're going to release co2 which makes your bread rise or in the case of this we get our bubbly from the co2 as well as the alcohol found in these kinds of drinks so that's alcohol fermentation and the idea again is when there's no oxygen available and because you don't have oxygen or you don't have mitochondria you're gonna go make nad plus this way all right so i want you to see a really goofy little video i hope that i do this right this time i know one time i made a video and i didn't include the music right so apparently it was really kind of strange you'd have to watch it on your own um so let me see if i can get this up for us here pull up this video for you okay i'm gonna pause this first hold on hold on there we go all right so i'm gonna share it for this one and i think i can share the com sound let's see if i truly did that okay so this song was written and performed by this young man he is a former student at stanford in biology and quite a talented musician and scientist he would learn a lot of his science by performing on the guitar and in different groups um he also has done a number of other pieces and is now an artistic director for part of npr and uh a number of other shows so there's a really great show on on vaccines and the pandemic and he did the art for it so in any case um it's just kind of a funny song to watch but i want you to see how this is connected to what we're talking about okay so let's see make sure we're sound sharing good and hopefully you can see the rest of the video here okay so here we on go the 17th the feast of saint patrick i will raise up a beer and i'll raise up a cheer for saccharomyces [Music] but my friends that isn't all [Music] fermentation and adhd my intestinal wall absorbs that ethanol and soon it passes through my blood-brain barrier there's a girl in the next seat who i didn't think that's sweet but after a few drinks i want to marry her i guess it's not surprising my dopamine serotonin is my government is impaired and my confidence is oh when that ethanol is in me sun shows up in my kidneys and inhibits vasopressin my greens are decreasing but foreign [Music] glycogen is soon depleted and tomorrow when i'm sober i will also be humble cause i pushed electrolytes that myself is [Music] [Laughter] so i hope that you enjoyed that let's go ahead and move back to our lecture here did you catch a lot of things that we've been talking about i hope so it kind of gives you any idea where we've been kind of headed out over time right so last thing i want to talk about is okay so you've eaten something today what about all the other biomolecules that you've had i mean we've only been talking about glucose is that what makes a taco or a burrito no of course not there's going to be a lot of other things that are involved in your food and so um when we think about this what we're going to be looking at is breaking down larger polymers in the monomers so what is this first one do you recognize this what are these right here well you can see there's a long chain that's going to be our protein what are the monomers we'll break them down into with protein digesting enzymes we'll break them down into their amino acids all right so what is this polymer here so that polymer we're talking about carbohydrates in terms of polysaccharides or disaccharides and what are these monomers called monosaccharides that are going to be broken down by carbohydrate digesting enzymes what is this right here well it looks like it's some kind of nucleic acid and since it's single stranded it probably is an rna but this is our nucleic acid what are those monomers do you remember looking at those that is going to be our nucleotides and we had enzymes that break those down see how they're very specific from each other with each other and then here we've got our lipid looks like it's a triglyceride and it's going to be broken apart into its pieces it's got its glycerol and it's fatty acids so that's how we're digesting all these enzymes some of these are going to happen at different stages than others for example the polysaccharides they get started right away in your mouth if you take a simple um cracker put it on your mouth in your mouth on your tongue without any salt on it or anything you won't really taste anything but as soon as you leave it there for a few moments that amylase is going to break down amylose that is the carbohydrate digesting enzyme that breaks down starch and then you'll start to taste monosaccharides you'll start to taste sweet and that's just because of what's happened in your mouth try it with a piece of bread hopefully something that's not too sweet already because a lot of american bread is very sweet now noticing here these are the parts we just talked about carbohydrates triglycerides proteins we break them down into their monomers and of course this could be coming from peanuts right because it's um a good example of something that we'd eat so you'd have monosaccharides of course unless you're allergic to peanuts right those monosaccharides will be broken down through glucose and will go all the way through like we learned already triglycerides a little bit different glycerol is essentially a half of a glucose so that's kind of our g3p when we split it in half and it's going to go through the rest of the whole process of cellular respiration however the fatty acids they're just c's and h's they're much more like the acetyl-coa with just c's and h's on it so at some point they'll be broken down just a little bit more and then continue on the proteins well it really just depends on the amino acids in terms of what they're made of what their r groups are but we know the amino group has got to go because that's what is toxic to us so that is going to go out in the urine right away and then the other parts carboxyl group the c the h's and then the r groups are going to go into the different stages really depending on which they're most like and then ultimately everything goes through oxidative phosphorylation where we get atp so that's the end of section 4 study guide questions i hope this was useful to you i may be doing a second video of photosynthesis but we'll see how that goes okay um catch later bye