hi everybody and welcome back to miss Angler's biology class I am Miss angler in today's video we are going to be looking at anerobic respiration now before we start this video it's really important that you have already watched the aerobic respiration videos in particular the glycolysis video which I am linking above now you should go watch that first before you attempt any anerobic respiration now if you are new here don't forget to give this video a thumbs up and make make sure you're subscribed with your notifications turned on because I post every Tuesday and Thursday and if you are in grade 11 don't forget to get your hands on my cheat sheet study guide it's an incredible resource it makes studying so easy I've simplified even the most difficult topics like respiration so that you can get that distinction you deserve so let's dive into anerobic respiration now the word anerobic means without oxygen right so that's the oxygen molecule we don't have oxygen available to us now this is something that is very very misunderstood and I don't think a lot of people realize but glycolysis itself is an anerobic action there is no oxygen present in the glycolysis cycle if you're not so sure about that again go and watch my glycolysis video before we continue and a lot of people don't realize that because glycolysis doesn't require any Oxygen you can simply transition into anerobic respiration if you still don't have any Oxygen what do I mean by that well let's have a look at glycolysis remember glycolysis is when we take a glucose molecule we're going to break it down we're going to make the uh hydrogens accessible and usable for us later on and we're going to make a pyruvate at the end if there is oxygen present then glycolysis will go onto the crebs cycle right but if oxygen is not present that is when we enter into fermentation and we're going to look at the two types of fermentation if you are a plant or a yeast you're going to do alcoholic fermentation and if you are an animal you are going to do lactic acid fermentation so let's have a closer look at alcoholic ferment now where does this occur this is going to occur in microorganisms mostly we see this in yeast we can also see this in Plants now again all forms of anerobic respiration always begin with glycolysis so a a common mistake that a lot of people make in exams and tests is um they will say uh where does glycolysis end and people talk about aetl co-enzyme a being where it ends which is actually not true glycolysis ends with two pyruvates that's where it ends because there's no Oxygen present only if there is oxygen will go into the crab cycle but for now remember we are staying in just the anerobic pathway now that means at this point if you have a look here if there is no oxygen present what's going to happen is the following we are going to take our glucose molecule we are going to break it down and simplify and we're going to produce two ATP molecules via phosphorilation which if we don't know what phosphorilation means it essentially means we are taking a phosphate ion and we are adding it onto a molecule there's our phosphate and we're adding it onto our a DP to make ATP remember the d stands for D and the T stands for try so what we're doing is we're taking two phosphates and we're adding another one to form a TP and this is formulating into energy but it's not a lot of energy it's only two it's not a lot on the other side we're also forming nadh because we're harvesting those hydrogens why hydrogens well hydrogen ions are really energized right I want you to think of them as um little work bees that are going to make um the uh energy actually transform into usable energy like the hydrogens are the things that we need in order to unlock the stored energy in the glucose that we consume now when we go through glycolysis we end with a pyruvate and some carbon dioxide is produced it is at this point that if there is no oxygen at this point here we can now successfully enter into alcoholic fermentation if we are a plant so what happens next is we're going to end up losing some of our oxygen molecules and we're going to end up with two acetal alahh our nadh that we made earlier remember that hydrogen that we needed that hydrogen is going to basically act as remember like a a transfer of energy like it's going to input a chemical change we need that hydrogen for the chemical change and we end up taking that hydrogen adding it on and we get two ethanols now if you have a look at the summary at the bottom here of the byproducts and the reactants it's really important to know what goes in versus what comes out because often in exams we are tested on the substances that come out via a experiment and I'm going to get to that later in the video now moving into lactic acid fermentation this is what we see in animals now animals produce lactic acid when they don't get enough oxygen basically they're in what we call an oxygen debt oxygen debt happens when an organism is exercising or it is running for long periods or it's lifting heavy weights or it's moving things around and the oxygen input is not as great as the carbon dioxide output and and basically happens over time is you produce lactic acid in order to indicate that your body can't continue performing your muscles are basically getting tired and they need to stop and the lactic acid fermentation is happening inside your muscles now once again we still follow through with glycolysis as always and we end up with two pyruvates as we did before but because we are in an animal when we get to this decision Point here and there is no no oxygen available instead of creating ethanol we are going to create two lactic acid molecules again this is really important to take note of in our summary of reactions here with our reactants and the products that we produce now one of the most common questions I get asked is how are we going to ask this in the exam well other than it being very straightforward and them saying well label this diagram or fill in the missing product products and the byproducts or the reactants the most common way is with an investigation now this investigation here is the classic investigation that they use and sometimes they just modify it by slightly changing the substances or the apparatus maybe they'll put in a bean instead of a yeast but it's always the same idea that we're testing so what we have in front of us here is two test tubes the first test tube test tube a is a test tube made out of glucose and yeast now the moment you see the yeast you must know that this is alcoholic fermentation and that's really important because that's going to tell you what the byproducts are remember alcoholic fermentation is going to produce ethanol and carbon dioxide now why is the glucose there that is going to be a food source or an energy source for our mixture of yeast now something I want to also note here which isn't listed on here but I'd like you to know this is they often tell you that this solution has been boiled now a lot of people misinterpret this what that means is the solution is boiled to kill other organisms in specifically other micro organisms and that is because when you want this um investigation to work you don't want any other organisms to affect your outcome you only want the yeast to be respiring or in this case anerobic respiring okay that's the first thing next thing why is there a layer of thin oil another question that they love to ask so the oil is there in order to keep out oxygen okay it keeps the process anerobic okay that's important last but not least um the clue that they have also boiled this is that it is in a boiling tube but they will also probably give you a little explanation that it has been boiled now test tube B this one is not labeled and sometimes you should expect it not to be labeled but this mystery substance in test tube B that is lime water now lime water is used to test for carbon dioxide and what happens is it goes from being clear to milky white in the presence of carbon dioxide and so that's how you test to see whether or not alcoholic fermentation is taking place because if we follow the steps the yeast will ferment inside of the mixture over here it will give off carbon dioxide that carbon dioxide will then move through the tube down into the tube next door turning the mixture from clear to milky white which also reminds me that this rubber stopper up here also prevents any oxygen from getting in as well and so that only carbon dioxide builds up one last important thing is that if the lime water doesn't change and it stays clear then there are some indications that something has happened maybe they boiled not only the glucose mixture but they boiled the whole mixture with the yeast and the glucose which means they killed everything and if they kill everything then there should be nothing left behind to respire or anerobic respire and the lime water will stay clear now as always I i' like to finish up my lessons with a quick terminology recap there was only a few words in this section that we need to just revise and that is of course glycolysis which is the process of taking a glucose molecule in an anerobic State without oxygen and forming two pyruvic acids or pyruvates we then looked at the two kinds of fermentation which is our lactic acid which we see in animals and our ethanol or alcoholic fermentation we see in yeast and plants the main byproduct that we test for is carbon dioxide and we use lime water to do that because lime water will go from clear to murky in the presence of carbon dioxide now if you like this video don't forget to give it a thumbs up and make sure you're subscribed with your notifications because I post every Tuesday and Thursday and I will see you all again soon bye