okay this video is gonna go over the basic introduction to chapter 5 and in chapter 5 this is we're gonna start talking about those biologically relevant molecules or the macromolecules that we've been sort of building up to as we progressing through this semester so all the way things are made out of four classes of large biological molecules these are going to include your carbohydrates your lipids your proteins and your nucleic acids remember a nucleic acids are the same thing as your DNA and your RNA now for the sake of this course I'm going to categorize all four of these classes of biologically relevant molecules as macromolecules macro for big molecule for molecule even though some of the molecules within these four categories might not be macromolecules than that be by just for the sake of simplicity what we're gonna call all four of these categories of biologically relevant molecules macromolecules now as we have been discussing in Chapter four remember we talked about organic molecules and the fact that they have this carbon skeleton and attached to the carbon skeleton you can have a number of different functional chemical groups all of these molecules are fall into these four classes of biologically relevant molecules have unique properties and these unique properties arise because of their carbon skeleton as well as those chemical groups that are attached to the carbon skeleton all right now many of these macromolecules are also built as polymers and the way that we define a polymer is it's a long molecule that consists of many similar building blocks these similar building blocks would give them the name monomers so mono one poly many you can use many of the monomers to build a really long polymer made from many of the monomers my analogy here is Legos right if you remember playing with Legos as a child you probably remember having those little you know four part square go blocks they come in different colors right your red your yellow green and blue all of the individual Lego blocks would be considered your monomers now you can take a whole bunch of them right and build them all together to form a tower for example on the tower would be the equivalent of a polymer made out of the individual Legos which are the monomers now of the four biologically relevant molecules that were talking about in this chapter three are those four classes the molecules are built as true polymers right so these three classes would include the carbohydrates the proteins and the nucleic acids so the one category that is not actually built as true polymers would be the lipids we're still gonna discuss lipids but again remember they're not built as true polymers now much like our building blocks right you can imagine that if you have a big pile of Legos celexa the Legos aren't going to build themselves into a tower right you need some sort of catalyst some stimulus to you get them built right maybe a four year old but in the case of cells right when you're building these polymers these big macromolecules again you need some sort of catalyst less catalyst typically comes in the form of an enzyme so an enzyme is going to be a specialized macro molecule that's gonna speed up chemical reactions such as those that either make the polymer or break the polymers so this leads us to a discussion of what kinds of molecules will make and break the polymers there's a specific kind of chemical reaction that does each so anytime you want to make a polymer you're going to be using a dehydration synthesis reaction typically when you hear the term dehydration you would think loss of water right or lack of water that's in fact exactly what happens in a dehydration synthesis reaction you're going to have the linkage of two monomers together to form a covalent bond between them this happens through the resulting loss of a water molecule when you want to break a polymer you're gonna do exactly the opposite so in this case you're gonna go through a hydrolysis reaction hydro meaning water lysis we're going to come back to this term multiple times through this semester the lysis means to break so anytime you're gonna go through hydrolysis you're gonna use a water molecule you're gonna break it and at the same time you're gonna use that to break apart monomers from a polymer let's take a look and see what this looks like using actual pictures instead of words so in this particular slide we have an example of both a dehydration reaction and a hydrolysis reaction you'll notice the dehydration reaction up at the top right so here we're going to have that short whoops we have that short polymer on the left-hand side right you can see that it's already built using those three monomers strung together we want to add a fourth monomer the unlinked monomer in this case we're building a larger polymer so we're going to be using a dehydration synthesis reaction to do this we need to remove a water molecule so you'll notice the hydrogen and blue there from the short polymer and a hydroxide from the unlinked monomer those make h2o so we can remove those atoms out the human molecule and as a result we're gonna link then the third monomer with the fourth monomer creating a slightly longer polymer longer by one monomer for instead of three hydrolysis reaction is the complete opposite of this right here we are going to break apart a polymer and we do so taking one monomer off at a time so in this case hydrolysis requires the addition of water to add water in and you end up breaking the water molecule into hydrogen and a hydroxyl group you're gonna add those to either the shorter polymer now or the unlinked monomer sort of satisfying the valence four atoms within both of those two components now each cell has thousands of different kinds of macromolecules so this is really makes life different this is how we show diversity now macromolecules are gonna vary among cells within one multicellular organism right so skin cells are going to have those macromolecules to help it look like and behave like a skin cell versus a muscle cell for example you can even have variability regarding a macromolecules within a species so this is what makes human beings makes us all a little bit different and then obviously macromolecules are gonna vary even more when you're looking between species as well now keep in mind that as we start discussing these polymers we can have a huge variety of polymers that can be built really from just a very very small set of monomers right my Lego blocks for example there were four different colored Lego blocks that's it that's my set of monomers but you know I could have many many different ways to combine just four different colored Lego blocks right probably create thousands of different towers using those same floor colors for the Legos much like DNA for example right DNA only has four building blocks Hayes t's c's and g's and yet only having that small little set of monomers we can come up with thousands of different kinds of genes so it really creates a live variability when it comes to being able to build these macromolecules