[Music] hi and welcome back to free science lessons by the end of this video you should be able to describe the role of ATP in energy transfer you should then be able to describe the role of hydrogen carriers in respiration now this is the first video on the topic on respiration restoration is a large topic with some Concepts that may look challenging it's very important that you watch all of the videos in order and do your best to understand each one it will also be much easier if you jot down key ideas from each video before you watch the next one and you may need to watch some videos several times to get the ideas if you do this you'll find that respiration is actually relatively straightforward okay now energy is essential for all living organisms for example energy is needed for processes such as active transport and movement we also need energy to build complex molecules such as proteins now the energy that we need comes in the process of respiration I'm showing you here the equation for the air robot respiration of glucose but you'll see that we can also use lipids and proteins and respiration in this topic we'd be looking in detail at the reactions involved in respiration and how energy is transferred from respiratory substrates such as glucose now a critical molecule in energy transfer is adenosine triphosphate or ATP I'm showing you the simplified structure of ATP here and you need to learn this ATP has the base adenine bonded to the pentose sugar ribose and together we call this part of the molecule adenosine on the other side of the ribose we have three phosphate groups now ATP is an energy carrying molecule if we react ATP with water the and phosphate can leave and this reaction releases energy this energy can then be used in the cell for processes such as active transport or movement reacting ATP with water is an example of a hydrolysis reaction and this is catalyzed by the enzyme ATP hydrolase which is also called atpase at the end of the reaction we've made adenosine diphosphate or ADP we've also released a phosphate ion now the phosphate ion has a symbol pi the eye tells us that the phosphate is inorganic in other words it's not bonded to a carbon-containing molecule so as you can see ATP is an extremely important molecule providing energy for processes that need it now once an ATP molecule has been hydrolyzed it then has to be reformed in order to be used again and ATP is formed during respiration using the energy stored in glucose when ATP is reformed energy from glucose is used to add a phosphate ion bark onto ADP this process is called phosphorylation now there are two processes in respiration that can reform ATP these are called substrate level phosphorylation and oxidative phosphorylation oxidative phosphorylation produces the vast majority of ATP during respiration we'll be looking at both substrate level phosphorylation and oxidative phosphorylation in later videos okay so as we've seen cells use the energy stored in glucose to produce ATP in respiration I'm showing you the structure of glucose here during respiration a large number of chemical reactions gradually break down the glucose molecule now a key idea you need to understand is that during some of these reactions a hydrogen ion is released this is called a dehydrogenation or oxidation reaction in this case the hydrogen ion has two electrons and I'm showing that here these hydrogen ions are rich in energy and they can be used to form large quantities of ATP this takes place during oxidative phosphorylation which we'll see in a later video now when a hydrogen ion is released it's added to a molecule called a hydrogen carrier a good example of a hydrogen carrier is the coenzyme NAD by adding the hydrogen with its two electrons to NAD we carry out a reduction reaction and we've made reduced NAD uced NAD is also called nadh but I'll be calling it reduced NAD in these videos and as you'll see later reduced NAD is a very important molecule in respiration in the next video we look at the first part of respiration which is called glycolysis foreign [Music]