hello and welcome to another one of the a Louisville biology lessons for free weirdness astrick today we're going into the final lesson in the carbohydrates series and that is polysaccharides so the polysaccharides are created by condensation reactions and you have multiple condensation reactions bonding together all of the glucose monomers and the three polysaccharides you need to know are all created from glucose monomers we have starch which is found in plants and it's a straw of glucose cellulose found in plants and its function is for structural strength glycogen is found in animals and it's a store of glucose now that's surface level information which you may have remembered from GCSE we will be going through today much more detail about the structure and how that actually links to these three functions so you'll need to have a copy of this table for your notes ideally it covers all of the key points that you would need to know from the specification and it compares it across all three polysaccharides so listen out for the monomers the bonds function location structure and for the highest marks it's linking that structure to explain the function so your mind is pausing out just to draw down that table as we go through slotting the information and at the end we'll go through the answers they start to begin with is created from two polymers both of those polymers are created from alpha glucose day and where the glycosidic bond forms is what creates a slightly different structure where you can get amylose and amylopectin we've already said it's found in plant cells specifically find in grains of starch inside of chloroplasts as an example and its function is an insoluble store of glucose so we'll look at amylose and amylopectin amylase is the first structure that we'll go through so it's created by saij reactions in this case for amylase the bond the glycosidic bond forms between carbon 1 and carbon 4 and this will happen over and over in a box it's a polymer it repeatedly happens now that unbranched chain of amylose coils up to make a helix so that is our structure amylase but there's also amylopectin now this also is formed by condensation reactions and this lower part you can see is one two four glycosidic bonds and we can tell that because you have this straight chain at this location though we now have part of it branching off and this is created by a 1 to 6 glycosidic bond so here we have carbon one of this glucose molecule and carbon 6 and G to that location it causes a branch so amylopectin is quite a branched polymer polymer and amylase is a straight polymer which spirals up the next one then is glycogen this is also formed from alpha glucose this time that is found in animals inside of the muscle and liver cells the function is also an insoluble store of starch so we are going to see some very similar structures so we can see that glycogen looks incredibly similar to amylopectin it has one two four glycosidic bonds and it has one two six glycosidic bonds what are the key differences though is glycogen has even more one to six glycosidic bonds compares to amylopectin so it's a highly branched polymer so this just gives an overview of how highly branched this molecule is it can still be compacted though so you can fit large amounts of glucose in a small space lastly then Cecilia's this is the most different in structure and therefore function cellulose the monomer is beta glucose this time so the other structural isomer its location is in the cell of plants and it provides structural strength so it prevents the cell from bursting when it becomes turgid with water so the structure then the betta glucose molecules formed by condensation reactions to create this long straight chain but they only contain one to four glycosidic bonds so you only have straight chains now those long straight chains of beta glucose line up parallel to each other and they are then held in place by many many hydrogen bonds and that's what these blue lines here are representing lots and lots of hydrogen bonds so if we were to describe the structure that we've got so far you'd get a mark for describing that there are long straight chains there'd be a second mark for pointing out that these chains are held by many hydrogen bonds to form a structure which we call a fibrin so all of these long straight chains held by many hydrogen bonds that is a fibrin now the way that this provides structural strength is because of the number of hydrogen bonds so I've pointed out here an individual hydrogen bond is weak due to the large number collectively they provide the strength to the cell wall so that's it that is our three polysaccharides and we'll go through the table so you can just check you have noted down all of the key information so first of all the monomers we have alpha glucose and starch and glycogen and cellulose is beta glucose the bonds that form starch forms one two four glycosidic bonds and amylose but one two four and one two six and amylopectin one two four glycosidic bonds only in cellulose and glycogen forms 1 2 4 and 1 6 glycosidic bonds but it'd be worth noting that glycogen has more 1 to 6 glycosidic bonds than amylopectin because that's going to come into explaining the difference between the structures function they starch and glycogen are stores of blue Ches whereas a delays is for structural strength in sir wall location starch is found in plant cells for example inside of chloroplasts cellulose is also found in plant cells inside of the cell wall and glycogen is found in animals in the muscle and liver cells so the structure starch is made up of two polymers of alpha glucose amylase which is an unbranched helix its unbranched because it only contains one to four glycosidic bonds amylopectin is branched and that's because it also has the one to six and that causes the branching cellulose is a polymer which is formed from long straight chains and those chains held in parallel by many many hydrogen bonds to form a structure called a fibrin glycogen is highly branched and is even more branched in amylopectin because it has more 1 to 6 glycosidic bonds so the last part then is the explanation of how the structure provides the function so the fact that it's a storage molecule starch the helix shape of amylose means it can be compacted down as if you were squashing a spring you're squashing it you can pax in it and that's the benefits it means you can fit a lot of glucose into a small space it has a double advantage day because it also has amylopectin which is a branch structure and having lots of branches coming off provides multiple exposed ends of the molecule and that provides larger surface area for enzymes to attach and therefore they can rapidly hydrolyze starch back into glucose to release the glucose to the plant if it needs it the last one here is insoluble now that is the same for all three so all three polysaccharides are insoluble in water and that is an advantage because if it doesn't dissolve in water it will not affect the water potential and therefore it won't affect osmosis now that's the benefit because it means you won't end up having excess water moving into the cells potentially causing them to burst or implants making them become turgid cellulase say cellulase the key point here is because those long straight chains are held in parallel by many hydrogen bonds collectively they provide the strength to the cell wall and lastly then glycogen this is also a branch structure but it's even more highly branched than amylopectin so that means it can be even more rapidly hydrolyzed back to glucose and that's an advantage because it's a storage molecule in animals and animals need to be able to move movement requires energy and glucose is needing a respiration to release that energy so that is why animals have a more highly branched store of glucose compared to plants so hopefully you found that a helpful overview of the polysaccharides or maybe an introduction and maybe look over again if you need to just check you've got all of those details in the box if not go on to practicing some the questions or even going on to a test now on the carbohydrates