[Music] hi and welcome back to three sighs lessons cold dot uk' at the end of this video you should be able to describe what happens in aerobic and anaerobic respiration now energy is really important in biology for example we need energy for movement humans and other mammals need energy to keep warm and we need energy for chemical reactions to build larger molecules for example proteins are made by chemically joining amino acids now the energy we need is supplied by a process called cellular respiration but we normally just call this respiration for short respiration is an exothermic reaction because it releases energy and it takes place continually in all living cells now there are two different types of respiration and you need to be able to compare them in air robot respiration the sugar glucose is reacted with oxygen gas this produces carbon dioxide and water and it releases energy so this shows the word equation for air wellbut respiration and it's essential that you learn this for your exam now one key fact is that aerobic respiration releases a great deal of energy but because the glucose molecule has been fully oxidized and you'll find out more about oxidation in my chemistry videos now in the exam you could be asked for the chemical symbols for the molecules in this equation the symbol for glucose is c6h12o6 and the symbol for oxygen is Oh - the symbol for carbon dioxide is co2 and the symbol for waters h2o so as we've seen if oxygens present then cells carry out air wellbut respiration but what if there's not enough oxygen well now the cells carry out an aerobic respiration we're going to look at an aerobic respiration in two different situations and the first is in muscles muscle cells need a great deal of energy for contraction but under certain conditions the amount of oxygen is limited we'd be looking at those conditions more detail in the next video on exercise so when is a shortage of oxygen muscle cells respire our nerve well Bentley and I'm showing the equation for that here do an anaerobic restoration and muscles glucose is converted to lactic acid and as you can see anaerobic respiration does not require any oxygen now one key fact is that an aerobic restoration releases much less energy than aerobic respiration but because in anaerobic respiration the oxidation of glucose is incomplete and again it's important to learn that now anaerobic respiration can also take place in plant cells and in yeast cells and I'm showing you that reaction here so as you can see in this reaction the glucose is converted to ethanol and carbon dioxide and again no oxygen is needed for this reaction now in the case of yeast this reaction is really useful anaerobic respiration in yeast cells is called fermentation we use this reaction to make alcoholic drinks such as beer the alcohol in these drinks is ethanol and that's produced by fermentation now we also use yeast to make bread and here the carbon dioxide produced by fermentation is useful this creates bubbles in the dal causing the bird to rise remember you'll find plenty of questions on respiration in my vision workbook and you can get that by clicking on the link above okay so hopefully now you should be able to describe what happens an aerobic and anaerobic respiration you [Music]