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Current time:0:00Total duration:13:06

Aerobic & anaerobic respiration

Video transcript

have you wondered why you need to breathe oxygen to stay alive how does oxygen help our bodies and what's the connection of this oxygen with the pain that you get sometimes when you are lifting weights or when you're running the cramps that we get how are these things connected the answer lies in cellular respiration so what is this let me start with what it is not respiration reminds me of breathing but let me tell you respiration is not breathing okay even though in our daily terms we might associate respiration with breathing but in biology there are two different things so what exactly is respiration then well respiration is a process in which the cells of your body your cells release energy release energy from glucose from glucose and in our daily terms we usually say burning calories right that's what we mean burning calories is respiration so this is where your cells are releasing that energy from the glucose and to be more clear what does this mean here is how I like to think about it so imagine this is your body the white dots represent the glucose inside your cells why do you need glucose because glucose has energy inside of it but their energy is trapped you can't use it now so to release that energy your cells carry out some chemical reactions they break down that glucose and that's what respiration is so respiration is where glue your cells break down that glucose and release this energy think of these yellow dots as energy and then your body can now use that energy for all the various activities it's that same energy that keeps your heart pumping and makes your brain work almost everything that you do comes from that energy and now we can answer why do we need oxygen if we go back this is our glucose molecules guess what cells need oxygen to break that glucose so this is where oxygen comes into picture so when we breathe ox the oxygen goes to all the cells then the cells use oxygen to break that glucose and release energy okay so why do we need to breathe oxygen because cells for respiration they require that oxygen to break the glucose so let's write this down as a chemical reaction now so what do you think are the reactants for this reaction well we saw that we need glucose so let's write that glucose is c6h12o6 this is the molecule of glucose and we saw that cells also require oxygen they also need oxygen so this is what they're taking and then what did we see what happens we saw that the oxygen reacts with glucose it gets broken down and energy is released right so what do we get when we break glucose in the presence of oxygen well we get carbon dioxide carbon dioxide is the gas that we throw out of our body we exhale that because we don't need it and we also get water water is useful for the body and all the cells so water is retained and most importantly we get energy this is the energy that you saw in the animation and you may have to balance this equation which I'm pretty sure you can do all by yourself but anyways this is our equation of respiration now how do you remember this well here's a trick if you look at this equation carefully it's a little familiar this is the reverse of photosynthesis remember photosynthesis that was where plants and all the green things will take up carbon dioxide and water and the energy from the sunlight and use it to manufacture glucose and give out oxygen right so respiration is exact opposite of that so in photosynthesis plants trap the energy from the Sun into glucose and respiration is the exact opposite they release that energy from glucose and we've talked a lot about how to remember the photosynthesis equation in a previous video on photosynthesis so if you need a refresher great idea to go back and watch that anyways plants also need oxygen to release their energy I should think plants only need carbon dioxide but they also need oxygen remember and similarly your cells also need oxygen to release that energy and since this is happening right now it's that same energy that's allowing your body to function and allows you to do all the work and it's the same energy that's allowing me to walk right now by contracting and relaxing the muscles of my body now since walking is slow this energy is sufficient but what happens when I start running well you can imagine as I start running I spend this energy faster that means these reactions now have to be carried out faster to give me more energy right so that requires a lot of glucose and a lot more of oxygen now glucose is fine because we have a lot of glucose in our body so there is no problem in with it because I ate a lot of food but what about oxygen oxygen comes from outside our body right so our cells start demanding now they say we need oxygen faster faster faster I need more oxygen faster and therefore thus the brain will say ok ok fine I'll give it to you I'll give it to you and brain forces you to breathe shallow make you breathe faster right and that's why we do this shallow breathing why do we do that because I want to get that oxygen fast and I want to release that carbon dioxide from my body very fast and so because of the shallow breathe because of this the shallow breathing starts but guess what even that is not enough for the core cells over here you see the core muscles of my legs are doing the maximum amount of work in running and so the cells over there need to release a lot of energy and even with that shallow breathing the cells are saying no this is not enough I need oxygen even faster even faster and the brain says I can't give you the oxygen that faster we can't breathe that fast that's not possible so what to do because they need that energy so the cells now start doing at a desperate attempt of getting energy they start conducting a different kind of respiration they start breaking down that glucose without oxygen so let's look at the reaction where glucose is broken down without oxygen and so when there is lack of supply of oxygen some of the glucose molecules get broken without oxygen and you know what we'll get this time will not get this because this needs oxygen we will get one product lactic acid that's what we will get lactic acid and it releases some energy energy and now you might see I'm returning writing energy very small over here you may not be able to see that also and the reason is the energy released is very small compared to over here okay and so that's why this kind of respiration definitely is not all that great but it's a desperate situation oxygen supply is very low and so some glucose molecules are broken this way to give that extra energy this is what gives you that boost okay and if you keep on working out then this reaction keeps on happening and as a result lactic as it starts getting built up in your muscles so when I'm running a lot of lactic acid gets built up in my legs and it's that lactic acid that makes those muscles of acidic and causes that burn and causes that pain and sometimes it also causes cramps so it's the lactic acid that does that okay now of course recent studies show that lactic acid may not be the culprit but our syllabus has not caught up with the recent studies so in your exams if they ask you what causes cramps in athletes our answer is going to be lactic acid okay and so now you can see your cells can break down glucose in two different ways one by using oxygen and one without oxygen so we need to give them names the one where oxygen is used we call that as Arabic respiration so this is called aerobic and the word aerobic kind of means in the presence of air and air here refers to oxygen and since this respiration does not involve oxygen in it it is called an aerobic so it's called an aerobic without oxygen or it's also called it's also another name it's called fermentation they're both same things fermentation so this needs no oxygen that's a great thing but it builds up lactic acid and very little energy is produced now lastly there is another possibility for anaerobic respiration which we our muscle cells our cells can't do it but some microorganisms and fungi the most famous one is yeast so this happens in yeast they can also perform anaerobic respiration meaning without oxygen but they don't get lactic acid you know what they give when they break glucose they give out carbon dioxide so they give out carbon dioxide plus a very important product called ethanol ethanol and again plus energy if it's respiration it has to release energy again very tiny amounts of energy you may not be able to see this but that's energy okay very small compared to this now what is this ethanol now you learn a lot about this in chemistry that ethanol is a kind of an alcohol there are different kinds and this is the one that people consume and so you can see that yeast has a lot of importance in alcohol industry and how do we remember this reaction now well I like to imagine a picture of a bottle of beer now we do not promote drinking or alcohol or anything but the picture helps to remember the fermentation of yeast so they put yeast in this beer right and that's what produces the ethanol and the carbon dioxide produces this froth but a more mind-blowing example of this is when I learned that yeast is used in bread and that's what makes it fluffy so when they prepare the dough of that bread they add some sugar and yeast to it and then they let it sit for a while the yeast starts breaking down that glucose from the sugar and causes carbon dioxide to be released from inside and that carbon dioxide since it's a gas it makes that dove rise then they start baking it maybe by putting it in an oven and once you start heating it the carbon dioxide gas starts expanding even more and eventually at a particular temperature both of them start escaping from that leaving behind air spaces and that's the air space that you see in that bread which makes it spongy and fluffy beautiful right and so both of these are fermentation or anaerobic reactions this one is a lactic acid fermentation and this one is called alcohol fermentation so that's pretty much it so let's summarize what did we learn in this video we saw that respiration in biology is not the same thing as breathing it is processed where cells release energy from glucose and one way of doing that is in the presence of oxygen which we call it aerobic respiration which gives the maximum amount of energy and how do we remember this I remember this as the opposite or reverse of photosynthesis equation and then we saw when there is shortage of oxygen sometimes our cells can break down glucose without oxygen this time we get lactic acid and a little bit of energy because it is without oxygen we'll call this anaerobic or fermentation and the way I remember this equation is I remember that I'm working out that pain is caused that cramps are caused by lactic acid even though it may not be really true for the sake of syllabus we'll use this and finally some other microorganisms like yeast can undergo a different kind of fermentation where they give us carbon dioxide and ethanol and again a little bit of energy and the way I remember this is I know yeast is used in alcohol industries and it's also used in bread making and the bread de Vries's because of the carbon dioxide gas that gets trapped