Transcript for:
Nucleic Acids and Proteins Overview

Hi this video is about nucleic acids and proteins and it's almost impossible to talk about one without the other so we talk about them together we are going to talk about several different types of nucleic acid but we're going to start by talking about DNA and RNA and the connection they have to proteins there's actually a video that I want you to watch I have posted a separate link and it's a really cool image that I'll discuss in a minute but it's from a video that really has nothing to do with the lecture I'm telling you today except that I love the image it paints of the relationship between DNA, RNA and protein so DNA is really the recipe for how to make your proteins it tells your cell the order in which to assemble the amino acids to make a protein so a protein is a chain of amino acids and we'll talk about that more in a minute DNA is the master recipe for how to make every protein in your body every time you need to make a protein that recipe on the DNA must get transcribed into a piece of RNA and there's a specific reason for that I'll tell you in a minute it then gets translated into the amino acid sequence of the protein so DNA becoming RNA is called transcription as you can see in the picture on the screen and then RNA becoming the protein is called translation we're going to talk a lot about this this semester because if there's something wrong on the DNA if there's an error on the DNA then you're going to make the wrong piece of RNA and then you're going to have the wrong amino acid sequence on the protein and that really is the basis for every single human genetic disorder so this is incredibly important to understand when something goes wrong mainly that you have inherited the wrong sequence on your DNA or you have a mutation that occurs during your lifetime on your DNA sequence that causes you to transcribe the wrong RNA which causes you to assemble the wrong amino acid sequence for the protein and the protein doesn't function correctly because it doesn't have the same shape and we'll talk about why that is okay so just to quickly tell you what nucleic acids include that we're going to talk about in this class we're going to talk about your genetic code which as I've mentioned is the recipe for how to assemble your proteins and that's going to include the DNA and your RNA we're going to talk about several different types of RNA namely we're going to talk about what's called messenger RNA that we abbreviate mRNA we're going to talk about tRNA which stands for transfer RNA and we're going to talk about rRNA which stands for ribosomal RNA so mRNA this is messenger RNA t stands for transfer and r stands for ribosomal we will not talk about the details of these three types of RNA until later in the semester when we talk in detail about transcription transcription and translation okay we're also going to talk about two other types of nucleic acid that are incredibly important we've already talked about these briefly and that is ATP and ADP ATP and ADP are both nucleic acids also that do something very different they are involved in the energy story in the cell so nucleic acids have a variety of incredibly important functions this is the link to the video i am going to post this separately but in this video I just want to quickly tell you there's this image of a castle and the DNA is locked in that castle and it can't leave it needs to get the recipe out to the chefs in the cytoplasm of the sea who need to cook the recipe so in this video a typical cell sorry for some reason I'm not drawing right now I'm like all over the place a typical cell would have a nucleus and in this nucleus is your DNA all 46 of your chromosomes all stretched out like spaghetti during normal cell function if this cell isn't actively dividing that DNA is all stretched out so that every time you need to make a protein an enzyme can get in there access that DNA recipe and read it and make a copy it makes a copy of just that one recipe for one protein we've used a term already this semester gene a gene is a region of DNA that codes for one protein so when it's time to make a protein you don't make a copy of all of your DNA you make a copy of just that one recipe okay good analogy is you want to make mac and cheese and it's on page 125 of a big cookbook you own you wouldn't start on page one and cook every single thing and then finally it's like here we are three months later we finally got to the mac and cheese now you're gonna just go to page 125 and you're just going to cook that one page right so that's exactly what happens when we need to make a protein we go to just that one region of the DNA and we make a copy just of that that copy is the messenger RNA it's taking the message from your DNA out to the cytoplasm where that protein is going to get assembled so here's the deal that the protein is going to get assembled out here on some important cell structures called ribosomes ribosomes are the site of protein assembly this is the assembly plant okay they don't magically make proteins they assemble proteins from the amino acids that you already have in your cell how do they know which amino acid to put first second third fourth hundred and fifth they know because that piece of messenger RNA is going to carry the message to the ribosome and tell it in which order to assemble so here I'm going to show just this one gene is going to make this little green piece of messenger RNA so I'm going to call this mRNA and it's a copy of just one gene okay that messenger RNA leaves the nucleus it finds a ribosome a ribosome assembles around the messenger RNA and it's going to read that recipe and it's going to start assembling a protein that protein is a chain of amino and the key is it's folded into a specific three-dimensional shape and we're going to talk a lot about this today the shape of that protein is very critical we've already talked about protein chip when we talked about pH and remember proteins function in a very narrow range of pH temperature salinity any of these factors that change can change the shape of the protein and it no longer functions if you don't have their correct amino acid sequence it will also change the shape of the protein and it won't function correctly and we're going to talk a lot about that so that protein is a chain of amino acids that chain of amino acids though before it folds has a different name and we're going to talk about that in a minute too but what I want to show you is that that ribosome is going to start assembling this protein and as it reads the messenger RNA it's going to move along and that protein is going to start emerging this chain of amino acids is going to start emerging okay and eventually it's going to fold into its final three-dimensional shape and we're going to get this fully formed protein in the video that DNA is locked in the nucleus they have this be a castle it's locked in the nucleus it can't leave and there's a little scribe who's throwing recipes out the window of the castle okay so those recipes are the messenger RNA so we're going to call those the recipes these ribosomes are the cooks okay and whatever recipe the cooks receive they cook it and those recipes are for proteins so castle the DNA is locked in the castle it can't leave so that scribes in there he's copying recipes from the cookbook he's throwing them out the window they go out here into the cytoplasm sea and those cooks start making whatever recipes they receive those cooks are the ribosomes they start assembling those proteins and cranking out as many copies of that protein as you need so please watch that video it's a very cool picture to have in your head it's very non-scientific but sometimes the non-scientific analogies really work okay so DNA codes from messenger RNA that messenger RNA is for just one gene not all of your DNA that recipe goes out to the cooks the ribosomes and they cook whatever protein is needed at that time so close relationship between nucleic acids and proteins okay here's a chain of amino acids when you recall that original chart we made about the macromolecules remember that the monomers for proteins are the amino acids so proteins follow this model of monomers linking together to form polymers so the monomers are the amino acids we have 20 different amino acids that make up our proteins and all 20 of those are listed at the bottom of this slide you do not need to memorize the 20 amino acids okay what you do need to realize is that each amino acid has a three letter abbreviation we will be using that later in the semester so when you see ala okay ala is not the name of the amino acid that's alanine so you just need to be aware that every amino acid has a three-letter abbreviation that stands for a longer name so 20 different amino acids that make up our proteins and again it's your DNA that's going to determine the order and number of those amino acids in a protein they have to be exactly right in the right sequence to give you the correct shape for that protein and we're going to see how that happens that chain of amino acids is the polymer and it's not really called a protein yet it's not called a protein until it folds until until it folds into its specific three-dimensional shape that just that chain of amino acids is called the polypeptide chain and you can see that term here so the polymer is the polypeptide gene the polypeptide chain is a chain of amino acids this is an amino acid and all 20 amino acids have the same basic structure they only differ in structure in one location and that is what we call the r group you can see this r at the top of this amino acid so all amino acids have this central carbon called the alpha carbon so central carbon the alpha carbon and then on one side is a carboxylic remember we saw a carboxyl group with the lipids but this is not a lipid we know this isn't a lipid because it's not a a long hydrocarbon gene attached to this carboxyl group instead we have for the first time an amino group okay so you can see why these are called amino acids because they have an amino group please from the very beginning i want you to realize an amino group and an amino acid are not the same thing okay amino group is just this nitrogen it could have two or three hydrogens depending on if it's ionized or not this particular one they're showing only has two you don't need to worry about those differences what tells you this is an amino group is that nitrogen right there it's a nitrogen with either two or three hydrogens attached the amino group this is a functional group it's not an entire molecule okay so amino group is different from amino acid this entire monomer right here is an amino acid okay and again we have 20 different amino acids that means we have 20 different R groups otherwise all 20 amino acids have the exact same basic structure so central carbon carboxyl group on one side amino group on the other side and then right here there's always just a hydrogen and then there's that r group what do i mean by that okay here are all 20 of your amino acids you do not need to in any way memorize all 20 structures of the amino acids but what you do need to recognize is you need to recognize that that's an amino acid and then if you have a chain of those it's a polypeptide chain those are both part of ultimately the intact three-dimensional protein so what's cool about these functional groups I'm sorry what's cool about these R groups okay different from functional group what's cool about these R groups is they're all different for all 20 amino acids and the R groups are what give each amino acid its unique chemical properties so our groups give each amino acid its unique chemical properties because all 20 are different so for example all those in yellow those are all hydrophobic the ones in green are all hydrophilic and then we have some that are charged let me show you those closer so these are the hydrophobic amino acids and when those are in a chain they tend to be repelled by water remember if something's hydrophobic it means it's nonpolar which means it's repelled by water it doesn't mix with water all of these proteins are in your body you've got water everywhere so guess what if those are in a chain they're going to kind of fold and tuck inside so that's going to affect the shape of the protein having non-polar amino acids in the chain is going to cause ultimately part of the shape of that protein okay on the outside of the protein we would tend to see the hydrophilic ones okay those can interact with water those are water loving and those will typically not fold in then we have some different charges on these amino acids so when you get them all in a chain they start interacting with each other and it's the interactions among the r groups that are ultimately going to cause that protein to fold into a specific three-dimensional shape so ultimately the final three-dimensional shape of the protein is the result of those interactions among the R groups of the amino acids in the polypeptide chain okay I always like to think of you have a bunch of preschoolers and you tell them to line up and hold hands so they're all in a line and they're holding hands just like the amino acids and that polypeptide chain okay and they all have a different R group sticking up here and those R groups all start interacting with each other it's impossible for them to keep their hands off from each other you get a bunch of preschoolers in a line they start poking at each other prodding each other pretty soon they're wrestling with each other and that's the same thing that happens with these amino acids in the chain I have a picture of that somewhere here okay so imagine this whole chain of amino acids they're showing it as a ribbon which I dislike in this picture but I couldn't find a perfect picture imagine all these amino acids in a chain some of them are going to hydrogen bond with each other some are going to ionically bond the the hydrophobic ones are going to tuck inside the chain so ultimately this is what's going to result in the three-dimensional shape of the protein that protein is going to fold into that three-dimensional shape based on these interactions among the r groups if you have the wrong amino acid in the chain it is going to be a different interaction and that protein is not going to have the same shape you have to have the exact correct amino acid sequence for a protein so every human on earth if they're making a protein correctly we're all making it with the exact same amino acid sequence that's pretty crazy I just want to show you real quickly um this is a chain of amino acids so this is starting to build a polypeptide chain and remember we link monomers together to form polymers by dehydration reaction removal of water so here we go here's another example of it dehydration reaction removing water so you can see an H here and an OH here we're going to link those amino acids together how do I know this is an amino acid gene has a carboxyl group at one end and it has an amino group at the other end so no matter how long this chain gets there's always going to be an amino group of one end and a carboxyl group at the other end when they're all linked together so if you see this on the test if you see a chain of amino acids and I ask you what category a macromolecule is this okay you only have four choices carbohydrate lipid nucleic acid or protein you know this is a protein because it has a carboxyl group at one end and an amino group at the other end so we would say that this is a protein this shows you that three-dimensional shape of two different proteins okay so protein from a flu virus and then an antibody that is produced to combat that virus okay antibodies are huge in our world right now right we're all hoping we have antibodies now to coronavirus specifically the COVID-19 variety of the coronavirus and if you've either been infected naturally or you've had the vaccine you hopefully have antibodies against that virus you're you're not producing an antibody against the entire virus in the case of the coronavirus you are producing an antibody against a spike protein on the outer membrane of that virus antibodies are very very specific it's a it's a very tight shape fit so you have to make new antibodies for each specific type of virus and even different strains of that same virus in some cases that's why you need a different flu shot every year so antibodies are just one of the categories of protein we're going to talk about I'm going to go through the list of the different categories of protein in a few minutes first I want you to understand a little bit more about protein structure obviously you know when we were looking at a chain of glucose either forming starch or glycogen or cellulose that was a pretty simple structure okay it was just a chain of glucose sometimes it was branch sometimes it wasn't but protein structure has a lot more complexity so protein structure really um falls in it's categorized by either primary secondary tertiary or quaternary structure so there are four levels of protein structure that we're going to talk about oops so four levels of protein structure primary so primary means first secondary tertiary if you've never heard this word before it means third and then finally quaternary which means fourth those are the four levels of protein structure important to understand this the primary or first level of protein structure is simply what is the amino acid sequence of that protein okay and ultimately that determines everything so this is the most important part okay so the primary structure of a protein is our first level of protein structure and it is the amino acid sequence of that protein which one comes first which one comes second which one comes 104th that is what we call the primary structure of the protein again every one of those amino acids has an R group that interacts with each other to ultimately form the three-dimensional shape of that protein if even one amino acid in that chain is different or wrong then that protein will not fold the same and it will not have the same shape it will not have the same function okay primary structure amino acid sequence secondary structure is a little bit harder to understand and this is the result of hydrogen bonding between some of the amino acids in the chain and I told you at the very beginning we were going to see hydrogen bonding in three different types of molecule this semester water proteins nucleic acids here we go and we're looking at hydrogen bonds now and proteins in a polypeptide chain there are certain amino acids that will hydrogen bond with each other and result in one of two different repeating shapes one is this coiled shape called an alpha helix so this is the alpha sign right here so we can call that if we wrote it out it would be alpha helix so it's this coiled shape okay and this is beta so this little symbol is beta and we call it a beta pleated sheet and it is folded in a very specific configuration and again this is all the result of hydrogen bonding between specific amino acids to produce this pattern now some proteins will have a region of coiling some will have a region of coiling and folding maybe a protein has neither of these but when it does have this we call that the secondary structure of the protein okay so this protein is folding into its three-dimensional shape and then it's going to have a region that's folded and then maybe it has a region of coiling to ultimately produce the three-dimensional shape of that protein and when that happens that's called the secondary structure of that protein okay then finally the the third level the tertiary structure of that protein this is the three dimensional shape of the protein and it is the result of interactions among the r groups of the amino acids in the chain okay and it's also called the conformation of the protein so a lot of terms here are being used for the same thing confirmation means the three-dimensional shape okay which means the tertiary structure of the protein sorry I drew through shape there but those all really mean the same thing we can use those terms in in in I'm sorry interchangeably so when we talk about the conformation of our protein we're talking about its shape if we say the conformation of a protein has changed we mean the shape has changed all proteins for the most part have a very specific three-dimensional shape okay if that shape is different if that conformation is different it doesn't function correctly okay I've said it several times already but I'm gonna write it again shape is key in biology if something doesn't have the same shape it doesn't have the same function so shape is the most important thing for proteins some proteins also have what's called quaternary structure so this is not in all proteins in fact it's rare okay so not in all proteins and this occurs for specific proteins that consist of more than one polypeptide chain okay so most proteins are a single polypeptide gene folded into its final configuration okay but some proteins consist of multiple polypeptide genes and when that happens we say that protein has quaternary structure I'm going to give you two classic examples of that this is collagen which you know is part of your skin okay it's also part of your tendons and ligaments collagen is a very important connective tissue in your body and it is three polypeptide chains and they're actually braided together so rather than just being one polypeptide chain that's folded into a specific configuration there are three that are braided together so this is a very strong connective tissue so we would say that collagen has quaternary structure because it consists of more than one polypeptide gene this is hemoglobin it's on your red blood cells and it carries oxygen it's very important protein in your body and it consists of four polypeptide chains you can see two of them in purple and two of them kind of turquoise okay so one two three four separate polypeptide chains that make up that protein so we would say that hemoglobin has quaternary structure it also has primary structure it has some secondary structure it has tertiary structure just like all proteins but then it has this fourth level classic example that involves hemoglobin this shows you the critical importance of amino acid sequence in the final shape of that protein so red blood cells have this carrier protein called hemoglobin that carries oxygen and that amino acid sequence just like all proteins has to be exactly correct you can see in this picture that that sixth amino acid is normally glutamine but you can see this mutation this change in that amino acid sequence has the wrong amino acid in that place it has valine instead this is a DNA mutation that is inherited and it's called sickle cell disease one amino acid is different is incorrect okay and it's due to the wrong sequence on the DNA and it's inherited sorry it gets a little squirrely at the bottom here it doesn't want to write correctly I shouldn't be writing this close to the bottom okay one amino acid is incorrect due to wrong DNA sequence that's inherited and this can this shows you the power of just one amino acid being wrong one amino acid being wrong means the hemoglobin has the wrong shape and hence the entire red blood cell has the wrong shape so you can see that sickled as sickle as you know has that half moon shape and that's why it's called sickle cell disease the red blood cells have the wrong shape they have very reduced oxygen carrying capacity and again showing you one amino acid wrong in that protein folds into the wrong shape that protein doesn't function correctly we'll look at many many examples of that this year in this semester I mean and again this is the basis for almost every single human hereditary disorder the wrong DNA sequence ultimately results in the wrong messenger RNA sequence which gives you the wrong amino acid sequence in the protein very very important to understand of course we've talked about that you can have a normal protein that experiences a change in pH or temperature and it causes that protein to be denatured so i don't want you to forget those terms that we learned back when we talked about pH during the properties of water that denaturation can be due to change in temperature so if you put an egg white on a hot pan you have witnessed denaturation of a protein you've seen that protein change shape it's it goes from clear to opaque white very quickly due to that heat unraveling denaturing that protein okay we also talked about change in pH causing this you could also have change in salinity so increase in salts can can cause this if you've ever put salt on fish or other meat it starts to break the proteins down and tenderize it almost cook it and and that's why when you put lemon juice or lime juice on seafood to make ceviche or something else you notice a change in the color of that fish or that shellfish and um that's a change in pH due to the acidity of that lemon or lime juice so that's denaturation it really changes the three dimensional shape of that protein and it no longer functions correctly okay what do we mean by proteins i want to just quickly talk about the different categories of protein here they are all together there's a lot going on on this slide but don't worry there are separate slides for each of these as well sorry just keep checking to make sure my microphone is still working correctly because it tends to decide to just quit right in the middle of a lecture sometimes okay the most numerous proteins in your body are enzymes we're going to talk a lot more about enzymes this semester but important to realize enzymes are catalysts for chemical reactions they cause chemical reactions to take place with less energy required and a lot of chemical reactions in your body require enzymes to occur without the enzyme the reaction never happens that's a very important category of protein in your body here's an example of digestive enzymes hydrolyzing your food molecules so with the help of water um so this would be an enzyme plus water in this example to hydrolyze so this is hydrolysis remember i said hydrolysis requires enzymes we talked about the digestive enzymes that do hydrolysis in your digestive system so enzymes are critically important in facilitating chemical reactions in your body and those are a category of proteins we have storage proteins that are actually a storage form of amino acids if you think about an egg white there are enough proteins in that egg white enough amino acids to build a whole critter so whether it's a reptile a an amphibian a bird a fish any kind of animal that requires an egg to develop an insect I mean everything up until mammals requires eggs okay so sea urchins um everything all invertebrates require eggs and in there are amino acids in that egg white that builds that organism another form of storage protein would be the milk protein for mammals so the the casein that's in that milk helps build structures in that developing baby and that's a trait unique to mammals only mammals have milk structural proteins actually form structures in the body so keratin and collagen would be good examples of structural proteins you can see that connective tissue that is comprised of collagen we have contractile proteins that cause movement so not only in your muscles but also in the cell you're going to have these things called motor proteins that we're going to talk about when we look at the cell more detail that help move materials around in the cell also entire cells can be propelled by cilia and flagella different ways for our cells to move so if you look at protists for example they use these motor proteins to actually move so contractile proteins are very important receptor proteins are on the cell surface and certain molecules bind to these proteins and cause a specific response so you can see these receptor proteins on a nerve cell here there are um signaling molecules that are connecting and attaching to those receptor proteins and causing a specific response spreading your cell membrane and when we start talking about the cell membrane coming up pretty soon you're going to see how important these proteins are in facilitating transport across the cell membrane if a protein recognizes a specific molecule it will move that molecule in or out of the cell we also just looked at a transport protein hemoglobin that transports oxygen so important transport proteins on the surfaces of some of your cells well actually on all of your cells okay then there are certain proteins that are hormones um we talked about lipid-based hormones remember estrogen testosterone progesterone cortisol those are all hormones that are made of lipids we also talked about insulin and glucagon that are hormones that are made of proteins so insulin and glucagon remember two opposing hormones that play a role in regulating your blood glucose levels and these are both protein hormones remember hormones are chemical signals they are produced in one part of the body and travel through the bloodstream to another target tissue to have an action somewhere else and then defensive proteins so defensive proteins are the antibodies very very specific shape they're these y-shaped proteins and they attach to a specific region of a pathogen or other foreign particle to keep it from being able to get into your cells so here's the list of proteins you should know this list of proteins so the different categories or types of proteins and no kind of an explanation for each one very brief just the level of detail I just gave you is is satisfactory okay again just a reminder that there is a strong connection between nucleic acids and proteins so this shows the DNA in the nucleus a piece of mRNA is made remember that mRNA represents just one gene on the pro on the DNA which codes for one protein okay so one gene is all we copy and that's the code for one protein that messenger RNA leaves the nucleus and a ribosome assembles around it the ribosome is the assembly plant for that protein we're going to see later in the semester there are some other key players here including transfer RNA which is not shown in this story in this version of the story this is the very reduced version of the story you'll get the details later those amino acids are just in your cell they're going to be carried to the ribosome by the transfer RNAs we're going to assemble a polypeptide chain with a very specific amino acid sequence that was determined by your DNA so the wrong base on the DNA means the wrong base on the messenger RNA which means the wrong amino acid sequence in that protein and you're going to see later in the semester exactly how that occurs so proteins and nucleic acids are very tightly linked let's look at the structure now of nucleic acids so the monomers of nucleic acids are called the nucleotides I'm sorry I'm trying to not touch the screen with my hand while I'm writing because then it really messes things up okay monomers are called nucleotides okay and the polymer which is a chain of nucleotides remember a polymer is a chain of monomers they're called poly nucleotides okay so this is a nucleotide for a nucleic acid okay so we're talking about nucleic acids now and we're not going to go into a ton of detail about the structure of nucleic acids yet you will get that later in the semester we'll talk about DNA replication we'll talk about transcription and translation that's when you'll get more detail about the nucleic acids but i want you to be able to visually recognize a nucleotide and realize that is part of the category macromolecules none as a nucleic acid okay so it starts with that sugar that pinto sugar remember pinto sugar means it's a five carbon sugar it forms this pentagon shape so this pinto sugar is at the center of a nucleotide which is the monomer for nucleic acids and that sugar can be either ribose or deoxyribose okay so if you think back to the carbohydrates lecture I showed you the structure of these two pentose sugars and I told you that these would be a part of DNA and RNA okay they're also a part of ATP and ADP as you'll see in a few minutes basic difference between these two sugars is that one has an o h and one is missing the oxygen so deoxy without oxygen if it just has an h right there that's deoxyribose that is a different sugar even just that subtle difference makes it a different sugar DNA is made of a different sugar than RNA okay so deoxyribose is found in DNA ribose is found in RNA and you're going to see that ribose is also found in ATP and ADP so ribose is found in three of the categories of nucleic acids that we're going to talk about okay then there's a type of base here it's called a nitrogenous base because it does have nitrogen as part of the base so you do have nitrogen as part of your nucleic acids as well as your proteins and you can see that there are several different types of base that this can be so remember how on the amino acids there were 20 different R groups well guess what for RNA oops for RNA there are four different nitrogenous bases I'm just going to call them bases and for DNA there are four different bases so similar to how we had 20 different r groups this is less complex okay so this can be one of four different bases if it's RNA and it can be one of four different bases if if it's DNA this shows you the structure of those different bases over here on the right there is some redundancy okay so for RNA I'm trying to decide where to write this okay so for RNA and DNA you can have cytosine adenine and guanine we typically represent those by just the letter okay so this could be if this was RNA we're talking about this could be a C meaning it's cytosine okay it could be an A meaning it's adenine it could be a G meaning guanine so if it's RNA there's going to be a fourth one and that is this one uracil okay so this could also be a U for uracil if this is DNA it would have a different sugar okay it would have deoxyribose rather than ribose and then the four different bases it could have it could have a adenine it could have C it could have G okay or DNA doesn't have uracil instead it has a base called Thymine so this would be a T instead of a U if this was DNA I want to actually in a minute draw those all out for you individually so you can see what I mean by that so pentose sugar a nitrogenous base and then phosphate group okay so finally we're seeing the phosphate group remember this was a functional group you had to learn in the intro to organic chemistry lectures phosphate group is a part of nucleic acids it's a part of DNA RNA ADP ATP in fact in the ATP ADP story that phosphate group is going to play an incredibly important role it's going to represent energy transfer so so so important so you're going to be seeing phosphate groups a lot when we start talking about energy it is part of the nucleic acid structure okay so a single one of these is called the nucleotide if you get a chain of them it's a polynucleotide if it's a single chain we're looking at RNA if it's a double chain we're looking at DNA so I'll show you that in a minute here's a blow up of just that nucleotide it's called the nucleus side um this region over here but don't pay any attention to that I don't use that term okay this entire monomer is called a nucleotide and then just realize that this region over here is where the base is okay I told you I was going to draw this all out for you I just want you to realize that when we're talking about DNA versus RNA if this was DNA we would have four different monomers and the only place they differ is at the base so I'm going to draw a very um reduced version I'm just going to draw a p with a circle around it to represent that phosphate group okay so this is DNA we have four different monomers they all have deoxyribose as the sugar so I'm just going to draw an h there okay and they all have a phosphate group all four of them so let's just go ahead and draw that part oops sorry I'm having to use room where I can find it okay so those are the four now here's where they all four differ is what's attached right here this base if this is DNA this can be a C G or T so adenine cytosine guanine thymine so A is adenine C is cytosine oh my just gets crazy down here okay G is guanine and T is thymine and we usually just represent it with the letter okay RNA also has four different monomers and they are made from a different sugar okay so even if they have the same base it's not the same monomer it's totally different because it's made from a different sugar okay so I'm going to draw them I'm really sorry that every time I touch the screen something crazy happens okay different sugar this is ribose not deoxyribose so it has an OH there sorry I'm drawing these very messy okay still has a phosphate group the only place these four monomers differ is at the base and that base is going to be a C G and there is no thymine in RNA there is uracil so U equals uracil okay this is very very important even though we have a CG a CGc g those are not the same monomer okay RNA is made from ribose sugar and DNA is made from deoxyribose sugar so DNA is made from different monomers than RNA that's very important to realize that's why I take the time to draw this all out okay so when when RNA makes a polymer it can be any possible order of these you could have 10 a's in a row and then a c or you know it can be any combination of A,C,G and U, RNA is a single strand or chain of monomers okay whereas DNA is a double strand and I'm going to show you what i mean by that this slide is just showing you again the difference in structure from deoxyribose and ribose two different sugars so even if they have the same phosphate group and the same base attached they're not the same okay I love this cute little picture of DNA versus RNA okay so DNA is a double strand RNA is a single strand also use different sugar deoxyribose versus ribose and you can see the four different bases so you can see three of them are the same but DNA has thymine okay and RNA has uracil different sugar ribose sugar deoxyribose sugar double stranded single stranded important to know the differences in structure between DNA and RNA this shows you the details of the DNA okay these are called anti-parallel strands they run in opposite direction so we say that DNA is is made of two antiparallel strands two antiparallel chains of nucleotides so you can see that the sugars are upside down um opposite of each other this five prime to three prime don't worry about that right now what you do need to realize though here we go this is our third time we're seeing this this semester hydrogen bonds connect the two chains this is very significant when we start making proteins or copying our DNA remember hydrogen bonds are very easy to break you have to go in and break these bonds in order to be able to have an enzyme read this DNA to make messenger RNA or read this DNA to make a copy of the DNA so the two antiparallel strands are connected by hydrogen bonds this is kind of the more cartoony version and you can see all they're doing is the side ladder this is really the sugar and the phosphate so the pentose sugar and the phosphate group and then this is just the bases that are sticking out in the middle and they're connected by hydrogen bonds you can see that A and T always pair with each other and G and C always pair with each other so anywhere there's an A on one side okay there's going to be a T on the other G C C G A T that's called complementary base pairing complementary with an e they're not saying hey I really like your shirt they're complimentary and that they go together so complementary base pairs A and T always go together C and G always go together so there's an A on one side that means there's going to be a T on the other t a c g g c so if you know the sequence of on one side of the DNA you can predict the sequence on the other side I'm going to go back to a blank area here and let's just do that really fast so if this was my one side of my DNA I'm gonna write a base sequence I'll write this a little more clearly that's a G okay and I'm going to do another color for this okay so my other side we can predict what that would be based on complementary base pairing if I have an A on one side I'll have a T here, C goes with G, G goes with C G goes with C, T goes with A, A goes with T and those are hydrogen bonded together and we represent that remember with three dots A and T actually have two hydrogen bonds between them and C and G have three but I'm just going to draw one for purposes of this simplified picture so hydrogen bonds connect the two anti-parallel strands antiparallel can be written hyphenated or unhyphenated I've seen it both ways okay so DNA is a double strand of nucleotides RNA is a single strand there are three types of RNA we're going to talk about this semester and I listed those at the beginning so this is mRNA for short that is the copy of your DNA that carries the recipe out to the ribosome to make the protein ribosomal RNA is going to be part of the ribosome structure and tRNA transfer RNA carries the amino acids to the ribosome and you're going to see how that happens just a quick reminder that ADP and ATP which are the energy currency of the cell we're going to talk about this story when we talk about cell respiration and photosynthesis and you can see it's a new it's a nucleotide okay so they both consist of ribose sugar this actually is adenine so they both have a for their base okay and here we go adenosine triphosphate okay that means three phosphate groups triphosphate one two three that's ATP ADP adenosine diphosphate so this is ADP two phosphate groups this is going to be an important part of the energy story so I just want you to see the structure now realize that these are nucleic acids they're not involved in the DNA RNA story they are involved in the energy story they'll be involved in cell respiration and in photosynthesis so adenosine triphosphate three phosphate groups but otherwise it looks just like an RNA nucleotide that has adenine as the base so ribose sugar adenine three phosphate groups ribose sugar adenine two phosphate groups okay that's it for proteins and nucleic acids