this is an AP Bio review about nucleic acids I'm Mr W from learn biology.com where your journey to AP Bio success and a four or a five on the AP Bio exam is waiting for you don't delay sign up for a free trial today we guarantee success to anyone who completes our program do it now so we'll start by describing the biological importance of the nucleic acids these are the molecules of genetic information DNA is the molecule of heredity it's what passes from generation to generation it's the molecule that cells pass on as they divide and replicate within a multicellular organism RNA has other functions RNA is the hereditary molecule in some viruses never in cells and rna's key role is information transfer as in messenger RNA So within a cell here is DNA they're repository of genetic information it um has its information transcribed into RNA and then that RNA goes into the cytoplasm where a ribosome will translate that RNA message into protein RNA is a very versatile molecule it's not in the form of a double helix the way DNA is it can take many many forms and it can act as an enzyme catalyzing reactions um ribosomes are essentially catalytic RNA there are also other molecules called spom micro Aras that play a whole variety of functions and I finally want to say that this typically isn't put into this unit but ATP is a nucleotide monomer it's one of the monomers of RNA and it's the energy molecule of life it's how cells get work done what is the monomer of nucleotides what's its structure how are these monomers different in DNA and RNA the monomers are called nucleotides we just looked at ATP all of these molecules have a five carbon sugar that's shown at number two they have a phosphate group that's shown over here at number one and then there's one of four nitrogenous bases so the nitrogenous space doesn't have to have this structure note that the phosphate group is connected to a number five carbon whereas the nitrogenous Bas is connected to the number one carbon and when you learn about DNA replication you'll talk about things like DNA is replicated in a 5 to3 orientation and now you know that's about the five carbon over here and the three carbon over here in DNA the sugar is deoxy ribos and there are four bases adenine thymine cytosine and guanine in RNA the sugar is ribos and the bases are adenine uracil cytosine and guanine at learn biology.com we understand why students struggle with AP Bio it's a hard course but we have a plan for your success go to learn biology.com sign up for a free trial and complete our interactive tutorials and interactive AP Bio exam reviews we guarantee you a four or five on the AP Bio exam see you on learn biology.com now let's talk about the structure of DNA DNA consists of two nucleotide strands so easier to see in this flattened out version here's one here's the other um within each strand the bases are connected by um sugar phosphate bonds so here's a sugar here's a phosphate here's a sugar here's a phosphate same thing over here but the strands connect to one another by hydrogen bonds so here you see G connecting with C A connecting with t and those are rules to memorize adenine a always bonds with t c bonds with G they have complimentary shape their molecular dimensions are such so that they they fit nicely within the Helix that's more of a story for unit 6 um and note that these two strands fit together in an anti-parallel orientation in order for the nucleotides to form hydrogen bonds with one another they each need to be upside down relative to the other and that's what antiparallel is all about we'll talk about this again more in unit six but just to lay this down for right now DNA is directional notice that in a chain of nucleotides these are Arna nucleotides you can tell because there's urell the nucleotide sugar binds with a phosphate then there's a sugar there's a phosphate there's a sugar there's a phosphate well the enzymes that build DNA it's called DNA polymerase and these enzymes like all enzymes have an active site they only can work in certain orientations and they work by completely by feel and they can only add new nucleotides at the three end of a growing nucleotide strand so that's what directionality is all about all of these nucleic acids are built in the five Prime to three prime Direction want to learn more sign up for a free trial of the website that guarantees your AP biology success learn biology.com and watch this next video