In this video, we're going to talk about building and breaking down polymers. If a cell wants to build a polymer, it needs to perform a dehydration synthesis reaction. As its name implies with the synthesis part here, dehydration synthesis reactions form covalent bonds to link individual separate monomers together and begin to build a polymer. You can see that the synthesis here is all about forming and building a polymer. On the other hand, if a cell wants to break down a polymer into its small individual pieces, it needs to perform a hydrolysis reaction. Dehydration synthesis and hydrolysis reactions are opposites of one another. Hydrolysis has the root lysis in it, which is all about cleaving and breaking things down. Hydrolysis cleaves covalent bonds between the monomers and releases the monomers as separate pieces by breaking down the polymer. Once again, dehydration synthesis is all about building a polymer, whereas hydrolysis is all about cleaving or breaking down the polymer.
Let's take a look at our image down below to get a better understanding of the formation and breakdown of polymers. It's important to note that on the left-hand side of our image, we have 2 separate monomers, and on the right-hand side of our image, those monomers are now joined together covalently, starting to build a polymer. Of course, if we want to join together 2 separate monomers and begin to build a polymer, we're going to need a dehydration synthesis reaction. In the dehydration synthesis reaction, the hydroxyl group (OH) of one monomer interacts with a hydrogen (H) on another monomer, and OH and H release a water molecule. You can see the blue O here is coming from this OH and the yellow H is coming from this hydrogen. When water is released, as we see here, it dehydrates the molecule. The molecules are losing a water molecule, so the water molecules are being dehydrated, and in the process, it's synthesizing something. It is building a polymer, and that's how the monomers are joined together covalently here, as we can see.
If the cell wanted to do the opposite and break down this polymer into its separate individual monomers, it would need the backward reaction to release those 2 monomers, and recall that this is called hydrolysis. Once again, the lysis part is all about cleaving and breaking things down. This bond here can be cleaved or broken by using water, which is what the hydro prefix is for in front of hydrolysis. It's saying water is needed to cleave or break it down. A water molecule is going to be added to the process, and it's going to split the molecule in half. The biggest takeaway here is that if a cell needs to build a polymer, it will perform a dehydration synthesis reaction. If the cell needs to break down a polymer, then it's going to perform a hydrolysis reaction.
That concludes our introduction to this concept, and we'll be able to get practice applying this throughout our course as we move forward. So, I'll see you all in our next video.