in today's video we're going to look at naturally occurring polymers which are those that exist naturally in the environment and aren't man-made to recap polymers are just long chains of smaller molecules called monomers and although there are tons of examples in nature we're going to focus on three in particular polypeptides which are made up of lots of amino acids dna which is made up of nucleotides and carbohydrates which are made up of sugars you might remember from biology that if we take lots of amino acids and add them together in a long chain we get a polypeptide and when the polypeptide folds up or combines with other polypeptides we call it a protein because there are loads of different amino acids and they can combine in so many different combinations there are tons of different proteins and these different proteins do a wide range of different things including catalyzing chemical reactions as enzymes and providing structure and strength to tissues throughout our bodies when it comes to chemistry though we're more interested in the structure of the molecules and how they bond to each other for example if we look at an amino acid the most important parts are these two functional groups this carboxyl group which is sometimes called a carboxylic acid group and this amino group and these two groups will always be joined together by this central carbon there's also this group at the bottom which is called an r group and importantly this one changes depending on which amino acid it is which is what makes all the different amino acids different to help remember this structure just remember that we call them amino acids because they contain an amino group and the carboxylic acid group the key point to understand when these molecules have to join together to form a polymer is that these two functional groups allow adjacent amino acids to join together through condensation reactions this happens when this oh from the carboxylic acid group and this h from the amino group react together producing as a result the amino acids would now look like this which allows this carbon and this nitrogen to then bond together annoyingly though this bond has a few different names so you might see it being called an amide bond an amide link or even a peptide bond to write an equation for this we'll draw our amino acid on the left and show it forming one of its repeat units which would have to put in brackets plus an h2o molecule and because this is just a general formula we need to put ends before the amino acid in the bottom right corner of the repeating unit and before the water the next polymer we need to look at is dna this time the monomers are structures called nucleotides and importantly they all contain a small molecule called a base there are four different types of bases and we represent them with the letters t a g and c the rest of the nucleotide though which is this gray bit stays the same so effectively there are four different types of nucleotides one for each of the four bases and by combining these nucleotides in different orders our cells can effectively make different codes which we call genes to keep these codes intact and prevent them from getting damaged dna is actually made of two polymer chains that are linked together and this double strand naturally coils to form a double helix the last polymer to look at are carbohydrates the term carbohydrate is actually a general term that refers to a number of different polymers and monomers that we derive energy from and are all made of only carbon oxygen and hydrogen the polymers which we can call polysaccharides are things like starch cellulose and glycogen while the monomers which we call monosaccharides or just sugars include things like glucose and fructose just like with other polymers by combining the monomers together for example loads of glucose molecules we can make the polymers like starch anyway that's everything for this video so if you enjoyed it then please do give us a like and subscribe and hopefully we'll see you again soon