all right welcome back in the second video we're going to be looking at the first macromolecule type carbohydrates so what comes to mind when you think of carbs or carbohydrates for me a lot of it is what's shown in this picture like bread pasta I think of cake I think of fruit like apples pears grapes strawberries and so that's where we find carbohydrates and Grains fruits vegetables they give us energy through glucose a bunch of glucose molecules linked together that we can break down carbs are represented by this general formula where the ratio of carbon to hydrogen to oxygen is one to two to one and we see that here as well so for example glucose is c6h12 o6 you see that one to two to one ratio there are three main subtypes of carbs carbohydrates saccharide or saccharides that means sugar or sugars mono means one so monosaccharides are a single sugar disaccharides we'll see two something like two glucose molecules linked together and polysaccharides mean many sugars linked together sometimes you don't see this as frequently as before but in between two and three sometimes you'll see something called an oligo oligosaccharide and that means few few usually ranges it usually differs between the different kind of resource you're looking at but it could be anywhere from three to twenty ish number of carbohydrate monomers linked together monosaccharides are our first type single sugar they can have a carbon chain length of anywhere from three to seven carbons and usually these end with o s e like glucose sucrose fructose and this is in contrast to the enzymes we saw in the previous videos that often end in ASE like lactase we have the sugar lactose monosaccharides you'll see carbonyl groups in them this polar group if you have let's see something that looks like this we have our carbonyl group and that Central carbon is bound to something with a carbon attached to it and then a hydrogen on the other side if you see this these are aldoses or aldoses and indicated in green you're going to see this in the next slide in contrast if this instead of hydrogen here if you see a carbon if you see a carbon so two carbons that are attached to the central carbon in that case these would be ketosis and then when you look at the carbon chain length if you have three carbons we have triosis if this was five carbons long this would be at pentosis or pentoses and then if you have a six chain or a six carbon chain then we have hexocase so here's that in green we were looking at in the previous slide if you look at the carbonyl and what's attached to that Central carbon this makes it an aldose whereas here that Central carbon of the carbonyl group has a carbon on either side of it so that's a ketose so we can classify monosaccharides on the basis of whether they're an aldose or a ketose but we can also classify them based on their carbon chain length and this is what I saw earlier three five or six trios pentose or a hexos here we have three very common hexos monosaccharides shown so hexos because they're all six carbon chains and on the left I see a glucose I see galactose in the middle and fructose on the right it looks like the two on the left here's my carbonyl my two on the left look like these are aldoses and on the on the right I have a ketose and these are all structural isomers because they all have the same chemical formula c6h12o60 well it's already typed up and then on the bottom here oops so these are all structural isomers different arrangement of the atoms but they have the same chemical formula glucose it's a very common and important source of energy galactose we're going to see they're part of the disaccharide lactose lactose is made of galactose and glucose and we see this in milk and then fructose is found in fruits it's part of the disaccharide sucrose so sucrose is actually made of fructose plus glucose for the longer monosaccharides the ones that are five or six carbon in length these can actually exist in both linear and ring forms and when they're in aqueous Solutions we usually assume that they're in their ring structure so this is what their ring structure looks like I can see this linear form is turning into or converting into a ring structure if you have and let me number the carbons for you here this is carbon number one this little corner here two three four five and then this is six if the hydroxyl group is on the bottom or below carbon number one we call this an alpha sugar but this is carbon number one again if the hydroxyl group on carbon number one is above the carbon then we call this the beta sugar or the beta formation another way to tell Alpha versus beta is the alpha in the alpha State the hydroxyl group is opposite on the opposite side of carbon number six whereas in the beta formation it's on the same side as carbon number six over here we can see that the ribose ribose molecule down here which is a five carbon monosaccharide can also form rings in this case it's a five a five-sided ring and then we have fructose here on the right this is the six carbon ring excuse me six carbon monosaccharide that forms a five-sided ring here we're looking at disaccharides we're forming a disaccharide how do we form a disaccharide we do so by taking two monosaccharides and linking them together through a dehydration reaction so I see glucose that's one of my monosaccharides fructose another monosaccharide and I'm going to link them together covalently to form something called a glycosidic bond so glycosidic bonds are a type of covalent bond if I look really carefully and I see that this is carbon number one I see the hydroxyl group is down here so this is an alpha formation so this is an alpha glycosidic bond between carbon number one and over here between carbon number one and carbon number two so this is an alpha one two glycosidic Bond here if the hydroxyl group here in the glucose molecule we're actually above the carbon number one then that would be a beta beta linkage or beta glycosidic linkage here we see three very common types of disaccharides which I would like you to be familiar with we have maltose which is made up of two glucose monomers linked together through that glycosidic Bond or glycosidic linkage we've got lactose which is made up of galactose plus glucose and then we have sucrose sucrose or table sugar which is made of glucose and fructose a five-sided ring so glucose and fructose and again maltose is a grain sugar lactose is found in milk and sucrose is our table sugar that you usually see in your kitchen as I mentioned earlier sometimes we'll see oligosaccharides whereas oligo means few meaning 3 to 20-ish monosaccharides linked together but we don't see that as often anymore so we're going to jump straight to polysaccharides which are many monosaccharides joined together through those glycosidic linkages sometimes they're branched so you'll see branches of monosaccharides sometimes they're unbranched so you see single long chains and these can be made of all the same kind of monosaccharide like hundreds or even thousands of glucose molecules linked together or they can be comprised of different types of monosaccharides so overall they can be quite large in their size some common examples you'll see throughout our course and future courses are starch glycogen and cellulose all three of these are made up of lots and lots of glucose molecules linked together but interestingly they're found in different types of organisms so starch we find in plants plants store glucose in the form of starch that we eat and break down for energy plants also can store glucose in the form of cellulose and this we often refer to as fiber as fiber is mostly cellulose we can eat fiber but we can't break it down for us we can break down starch and glycogen and glycogen is how humans and other animals that have a backbone store glucose chitin is also a pretty common example and that one is not made of glucose monomers that one is made of something called n acetyl beta D glucosamine subunits and we'll see that in a later slide so amylose and amylopectin are two types or two forms of starch amylose is mostly unbranched glucose and they're connected by alpha 1 4 glycosidic linkages I can see this is on the opposite side or below carbon number one and the reason it's called 1 4 is because on the right side this is carbon number four whereas amylopectin is Branched so I can see the branches here whereas this one earlier was unchanged or unbranched and here we see both Alpha One four glycosidic linkages but also to form the branch or branches they have alpha 1 6 glycosidic linkages with carbon number six over here and carbon number one here and because of the way we join these glucose subunits they have a helical structure throughout so I can see that here as well as here glycogen is not shown here but it's similar in structure to the second one shown here amylopectin because glycogen is also very highly branched as I mentioned earlier cellulose is also a polysaccharide and we see this in plant cell walls cellulose is also made of a bunch of glucose molecules linked together and these are unbranched chains so that's why they look so linear here of beta 1 4 glycosidic linkages interestingly each glucose monomer is flipped next relative to the next one so they form a really dense fibrous structure and we'll see again we'll see these in cell walls of plants um so you see cellulose is the main component of wood and paper and we cannot break down beta14 linkages interestingly so when we eat cellulose in the form of fiber we can't break it down it just comes back out through you know when you go to the bathroom the herbivores like cows koalas they can and the reason they can is because they have special microbes in their stomach that break it down for them these microbes have an enzyme called cellulase that can break down cellulose into the glucose monomers interestingly termites by themselves cannot break down wood they actually rely on a microbe inside their gut that has the enzyme cellulase to break down the cellulose or the wood shown here is what you would see online if you were to just Google the three very common types of polysaccharides glycogen starch and cellulose and you can see how branched starch and glycogen are compared to cellulose and then here's another look where we have starch very branched also glycogen Branch as well made of those Alpha linkages and then cellulose which is very linear made of those beta linkages and we cannot break those down and the last most common type of polysaccharide we're going to be talking about in our class is chitin chitin is found in the exoskeleton of arthropods arthropods include things like insects and Crustaceans where the chitin is part of their exoskeleton and protects their inner body parts from the outer environment chitin is made of a modified sugar subunit this is called an acetyl beta D glucosamine you don't have to memorize that but I can see that besides the usual carbon oxygen and hydrogen atom shown here I also have nitrogen here we're also going to see that chitin makes up fungal cell walls in the future fungi include things like molds and yeasts and that takes us to the end of the second part of chapter three and the next or third video we're going to be looking at lipids which is our second biological macromolecule