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Current time:0:00Total duration:6:23

Video transcript

we've already seen multiple times that glycolysis is the process where we start with the glucose molecule which has six carbons and we're able to break it down into two pyruvate molecules which each have three carbons and in the process of doing so we produce a net of two ATP's we reduce NAD+ to NADH we're adding a hydride anion so this is a reduction this is a reduction going on right over there and then we say well what happens and of course we have the water some water produced and some hydrogen ions but then the next question is well what happens next and we could talk about cellular respiration and that's what will happen in many organisms including it's happening in my body right now in order for me to generate as much ATP as possible that's why I inhale oxygen because that oxygen is needed for cellular respiration but sometimes there isn't oxygen around or I'm the type of organism that just doesn't use oxygen or doesn't conduct cellular respiration now we've already seen one example of that and that was lactic acid fermentation it's a way of getting of recycling these NADH is oxidizing them back oxidizing them back to nad plus so this oxidation this oxidation from NADH to NAD+ this is what we do in fermentation actually both variations of fermentation that we're going to talk about and lactic acid fermentation we talked about taking the pyruvates to oxidize the NADH and in doing so the pyruvate turns into lactic acid and that's used in in yoghurt production and sauerkraut it's also used in your muscles when your muscles run out of oxygen if you're kind of sprinting or you're lifting some really really really heavy weights you probably have some lactic acid fermentation going on but now we're going to talk about another type of fermentation and that is alcohol fermentation alcohol alcohol or sometimes called ethanol per minute fermentation ethanol fermentation because when we talk about drinking alcohol we're talking about ethanol ethanol 4-man tation and as you might guess this is the process by which al was produced and things like Brenda it's used in baking a lot but let's first think about the reaction and then we'll talk about maybe where you might have encountered it last so we saw that pyruvate when we finish glycolysis we have that we have for each molecule of glucose we have two molecules of pyruvate and so each of these molecules of pyruvate the first step is they lose their carboxyl group right over here and that's facilitated by pyruvate decarboxylase you can this name is all about getting rid of a pyruvates carboxyl group and you can see when you remove a carboxyl group it's a carbon and two oxygens that is going to be and I'm not showing you the detailed mechanism here but that's going to be a carbon dioxide that is released and then what's left over what's left over and once again I'm not showing you the detailed mechanism but you can account at least for the various atoms what's left over is a tacit aldehyde acid aldehyde I have trouble I have trouble saying that and then the next step the acetaldehyde can be reduced one way you think about it you can say it's reduced by the NADH to turn into ethanol it's a similar mechanism to what we saw in lactic acid fermentation where we went from pyruvate to lactate acid but now it's acetaldehyde going to ethanol so this right over here this is this is a reduced reduced it gains a hydride one way to think about it is it's gaining a hydride anion and in the process of this is being reduced the NADH is being oxidized so this this is being oxidized and the whole point of this tell recent white occurs on is so that you can oxidize the NADH to have to have more fresh nad plus for glycolysis to occur again and as I mentioned in the video on lactic acid fermentation it's a little bit of a shame because the pyruvate has still has energy into it if you had oxygen around you could have cellular respiration you can go into the Krebs cycle the citric acid cycle and derive more energy from it the NADH also the process of oxidizing it in theory you can use it to generate more energy but we're not doing that when we do either type fermentation whether ethanol fermentation or we're talking about lactic acid fermentation but this is a process that has proven very useful for human civilization this right over here the most famous actor when we're talking about when we're talking about ethanol fermentation or alcohol fermentation is this character right over here this is a yeast cell yeasts are categorized as fungi that is a yeast cell it's it's a handful of micrometers in diameter although they can vary and variations of yeast are used in things like bread making and wine making or alcohol production beer whatever you want to talk about because what the U East does it uses it digests the sugar it performs glycolysis and then it performs alcohol fermentation what makes bread so fluffy is this step right over here when the carbon when the carboxyl group gets stripped off of the pyruvate facilitated by the pyruvate decarboxylase and the carbon dioxide gets released it makes the bread fluffy it bubbles through the the dough and gives it its nice spongy flavor but you also have FN all being produced so it's actually an interesting fact that a lot of bread you know I've been reading up on of it's a lot of the ethanol might get baked off but bread will usually have trace amounts trace amounts of alcohol in it so bread will have trace amounts trace amounts of ethanol in it because the whole process you're using yeast to leaven the bread to give it this fluffiness that yeast is performing glycolysis and alcohol fermentation it's producing ethanol in the process the carbon dioxide that gives the fluffiness but they're still going to be some trace trace amounts of trace amounts of ethanol now of course if we talk about wine production your goal is to get to the actual ethanol which we view is this traditional drinking alcohol so yeast plays a fairly important role in in our society
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