all right next we're going to move to carbohydrates in this video we're going to focus on monosaccharides so those are the monomer units of carbohydrates and then we'll move in future videos to derivatives of monosaccharides all right so as we're looking at carbohydrates they have a number of roles the most important role of a carbohydrate is energy storage and so this could be glycogen in animals or starch in Plants but it also has a structural component for instance cellulose and kiten those are both made of carbohydrates uh we also can recognize different cell types using carbohydrate markers and they are components of DNA RNA different co-actors um and other molecules that are important in your cell all right so monosaccharides or simple sugars cannot be broken down into any simpler sugars under mild conditions uh so typically your monosaccharide is going to be your basic building block so looking at terminology then oligosaccharide would be a few so this is usually 2 to 12 carbohydrates in a chain and then polysaccharides are going to be Polymers of our simple monosaccharides so that's going to be more than 10 typically we're looking in the order of hundreds of saccharides all right so when we're looking at monosaccharides we have two main types so first of all is we can represent any um saccharide monosaccharide as an open chain or a closed chain form when we're looking at monosaccharides the general structure is it's always going to have at least three typically six carbons in it and those carbons are going to have at least one oxygen on them each now there's going to be two main types the first is going to be an alos so we can see here in blue we have the alahh functional group so this would be an Aldos sh sugar over here on the right we have the ketos the keto form or ketos form so this would be a ketone because we've got a carbonal in between two carbons one way that you can recognize something as a sugar is by the ending so this o e so o e this o stands for sugar so when you're looking at names Al the o means you've got a sugar Al means it be an alahh and K would be a KET Kone so an Aldos would be an alahh sugar and a ketos would be a ketone sugar now anytime you've got four groups attached to a carbon you have the possibility of stereochemistry so in this case we've got two different aldoses so these um have three carbons each and then this Center carbon here is a stereogenic carbon so carbon number two it has four different groups on it it has an alahh an alcohol a hydrogen and a ch2 because of that we have stereochemistry at this particular carbon so this is a stereogenic center the way that we are going to name stereochemistry in alahh is not using RNs convention like in organic chemistry we named it based on D and L if your o group on your last chyo carbon in this case we only have one chyro carbon but if your o on your last chyro carbon is on the right we would consider that a d uh a d sugar if your o group is on the left we would we would consider that an L sugar all right a few more terminology few more pieces of terminology related to stereo centers okay so first we've got enantiomers enantiomers are going to be mere images of each other so as we look at each of the chyo carbons marked with an asterisk they each have opposite stereochemistry so here your o is on the left here it's on the right here your o is on the right here it's on the left so every single chyro carbon is the opposite these would be en animers of each other so here we've got D glucose and here we've got L glucose they are in aners of each other over here we have dumers so we can see that we've got uh four chyo carbons each in a dereamer some of your stereo centers are going to be the same and some are going to be different you have to have at least one one that is the same and one that is different which means in order to have a diamer you need to have at least two stereo centers in your sugar so you would need at least four carbons a tetos so over here uh we can see our last chyro carbon is on the right so this would be a d sugar and this is D Manos whereas over here again this is a d sugar as we compare each chyro carbon we can see the first chyro carbon is the opposite stereochemistry the next chyo carbon for galactose and Manos is the same the third chiro carbon is the opposite and then the last one is the same so D Manos and D galactose are considered dumers of each other because they have at least one stereo center that is the same and one stereo center that is different and in fact D glucose would also be a diomer of both D Manos and de galactose because they all have one stereo center that is the same and one that is different all right our last term is epimers epimers are going to be um when we have two sugars that have a difference in configuration at only one chyro Center and we can see that is in red here so D glucose and D Manos are essentially the same sugar aside from one stereo Center which is different we'll also run into another term um which would be animers and animers are going to be sugars that are exactly the same aside from a difference at the anomeric carbon they do not exist in the open chain forms like we have here an aner would only occur when a molecule like d glucose does a ring closing reaction and that will generate two new stereo centers and those two new stereo centers would be animers of each other all right so this is how we're going to generate that new carbon new chyro carbon so we H we can have cyclisation of both our Aldos and our ketoses and that will in introduce that new chyal syndrome so imagine we have an alahh and we've got an alcohol when this alcohol attaches to this alahh this alahh oxygen is going to become an alcohol when it grabs this hydrogen this carbon here which was SP2 hybridized and did not have any stereochemistry as it only had three groups attached to it now has four groups attached to it because it has four groups attached it can now have stereochemistry so we've got an alcohol going to a Hemi acetal ketosis can do the same thing we've got a ketone here instead of an aldah that alcohol can again attack this uh carbon and and give us this hemiketal instead of a Hemi acety because it was from a ketone instead of from an aldah okay so this is kind of giving us a look at how this cyclisation can occur so this is taking that straight chain and kind of curving everything around so here's carbon one where we had our aldah Carbon 2 carbon 3 carbon 4 and carbon 5 so in this case our alcohol here from carbon 4 can come and attack our Ketone or sorry our alahh in that this case and if carbon or the oxygen and carbon four adds that is what's going to give us these five membered rings or what we call furans If instead the oxygen that is on carbon 5 adds that's going to give us these Pinos Rings based on the pan ring and what you can see is we're going to generate a new chyro carbon at Carbon one where we previously had an aldah so this o group can go down or this o group can go up if your o goes down we call that an alpha at this anomeric carbon if your o group goes up that would be a beta at your anomeric carbon so these two molecules here would be anomers of each other because they're exactly the same aside from that anomeric carbon closing or that anomeric carbon being different here we've got the six membered ring and again carbon one is our anomeric carbon we've got our Alpha in this case because the O is going down and the beta because the O is going up so all four of these ring structures are possible from The Ring closing of D ribos based on whether your o adds from carbon 4 or your o adds from carbon 5 okay so when we are looking at our um open chain form and going to our closed chain form the way that this is written is carbon 1 is always going to be written in the rightmost position Carbon 2 is going to be to the left of it carbon 3 to the left of that carbon 4 to the left of that carbon five is going to be at the top of the Ring next to this oxygen so this o here is going to be the one that is going to attack our carbon and this carbon is this carbon one it is our anomeric carbon and then carbon six is going to be up in the ring these hexoses like we see here are going to be some of our most common sugars which is why you'll see this most often um and I just wanted to get you used to seeing these representations so this is the open chain form this is the closed chain form um and then we would call this a Hayworth projection now as you were looking at your open chain form all of your groups that are on the right are going to end up going down so we can see Carbon 2 had an O it is down relative to the hydrogen that is up this carbon 3 has a hydrogen on the right it is down relative to the O which is up the O group that is on the right is down relative to the hydrogen that is going up and then on C5 it's a little bit differently because this o is actually the one that is in the ring and the ch2oh is going up and your hydrogen is going to going down this would be for a d sugar for an L sugar it's still the O that attaches but your ch2oh would go down and your hydrogen would go up and again if your o group is going up that is beta and if it's down it is Alpha on your anomeric carbon we're just going to look at that ring CL step by step so again we've got our D glucose here carbon one is here Carbon 2 is here carbon 3 here carbon 4 is here carbon 5 is here and we've got some free rotation here around carbon 5 but it's this o that is going to become the oxygen in our ring and remember all the groups that are on the right end up in the down positions all the groups that are on the left are going going to end up in the up positions aside from carbon 5 where our ch2 will go up if it's a d sugar and it will go down if it's m sugar all right we now have everything in our correct configuration the O group from carbon 5 can either attack from the top on this carbonal or it can Attack From The Bottom on this carbonal and this carbonal will grab a hydrogen so if it attacks from the top that is going to be how you are going to get get your beta sorry if you attacks from the top that's how you're going to get your Alpha U because now this o here will go down if it attacks From The Bottom the O here will go up so we can see that this oxygen and this hydrogen end up being our anomeric carbons o