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Video transcript

we spent some time talking about hydrocarbons and hydrocarbons are interesting especially if you want to combust things if you want some fuel but now we're going to make things a little bit more interesting by adding things to the hydrocarbons and the things we're going to add we call functional groups functional groups and my goal in this video is to give you an overview of the major functional groups that you might see attached to carbon backbones that make the molecules interesting biologically now the first one I will focus on is an OHA up so you have an O H attached to a carbon backbone over here it doesn't have to be attached to a carbon backbone but the O H right over here this is called a hydroxyl group hi-hi Drakh SIL group and when it is attached to a carbon backbone like this one is then it turns the entire molecule into an alcohol alcohol this is an alcohol and this one in particular if you want the name we have two carbons on along its longest chain and it is an alcohol so we use a prefix F for the two carbons so let me write that down we're going to use the prefix F because we have two carbons here and we're going to say ethanol now what are the properties here well you have an oxygen which is very electronegative bonded to a hydrogen and to a carbon but the oxygen is a lot more electronegative than the hydrogen so you're going to have a partially negative charge at this end away from the hydrogen a partial positive charge at the hydrogen end and to a lesser degree at the carbon end - but hydrogen is even less electron is a less electronegative than even carbon and so this one so a hydroxyl group they are polar they are polar and because they're polar you can dissolve them into into water they are hydrophilic they can form hydrogen bonds so you can dissolve this now a similar a similar functional group or one that has somewhat similar properties is right over here and you might say wait why is this one similar I have I have sulfur here instead of oxygen but if you look at the periodic table you will see that sulfur and oxygen both have six valence electrons they both would love nothing more to then to grab or pretend to grab two other electrons and this is why they form they tend to form two covalent bonds and so this group right over here which is called a hydral group this is a self self hydral self hydral group it's it's kind of similar to a hydroxyl group with the one difference with the one difference that sulfur is electronegative but it is less electronegative than oxygen so you're still going to have a partially negative charge and a partially positive charge but it's going to be less polar so it's not quite as polar as if you had a hydroxyl group now when you have this self hydral group it's attached to say a carbon chain and when I when I use this R right over here when I have this R this is just shorthand for carbon and a bunch of other stuff I could have if I wanted to generalize an alcohol right over here I could have written R and then I could have written the hydroxyl group O and then bond that bond that to an H so over here the shorthand R would have been the shorthand for all of the R would have been the shorthand for all of this business all of this business right over here and so that's what we're doing over there I'm not saying that this R is exactly this it means it's some you know carbon backbone and some and other carbons hydrogen's and maybe other stuff maybe even some other functional groups but we're just focused on the self hydral right over here and so if you see something like this you'd say okay yeah this is still going to be polar but not quite as polar as if I were dealing with a hydroxyl group now over here we have a more complex molecule but this is a molecule that you run into probably on a daily basis this is the sugar fructose this is the sugar fructose and this is this is what it is not in a ring if you were to throw this into if you were to throw this into water it'll readily form a ring but it's not in a ring form you can recognize already the hydroxyl groups you have a hydroxyl group on this carbon you have a hydroxyl group on this carbon hydroxyl group on this carbon you have a hydroxyl group on that carbon you have a hydroxyl group on this carbon and then on this carbon you it's double bonded to an oxygen we call this a carbonyl group so this is a this is a carbonyl carbon eel carbonyl group and this is actually how you would tell a sugar it's like it look especially when it's in a straight chain all my carbons I have a Hydra have one hydroxyl on them except for this one it has a carbonyl group and one of the takeaways for a carbonyl group we've already talked about oxygen being very electronegative even more electronegative than carbon it's double bonds it's going to hog the electrons on the oxygen end so you're going to have a partial you're going to have a partially negative charge partially negative charge over here partially positive charge over here and so this this one is also going to be polar and in fact the entire molecule is very polar because it has all these hydroxyl groups on it as well but this is also going to give it polarity here and because this carbon has a slightly positive charge it is susceptible to nucleophilic attack and when you take organic chemistry you'll see the things that want to want to share that that have a predisposition to to share their electrons and a bond might want to come and and form a bond with this carbon and maybe one of these these electron pairs go back to this go back to this oxygen and maybe bond with something else but we'll talk about that in the future when we study some organic chemistry mechanisms the important thing here is just recognize okay I got some hydroxyl groups hey I got a carbonyl group right over here as well now this molecule this is an amino acid and you will see amino acids a lot when you study biology and this has actually a couple of interesting groups on it the first group of note is this is this stuff that I am circling in orange because you have a carbon that is you could say it's part of a carbonyl group but it is also it is also bound to a hydroxyl group it is also bound to a hydroxyl group right over there and when you have this configuration where you have a carbon bond double bonded to an oxygen and then single bonded to a hydroxyl group we call this a carboxyl group this is a car carboxyl carboxyl carboxyl group and one of the takeaways from this is that it is acidic because this can readily give up the hydrogen proton this oxygen we already know oxygen likes to hog electrons it can take up both of these electrons and become negative and actually there's actually resonance here because those electrons get shared throughout the group and actually even potentially even beyond the group but especially inside of the group then leaving the hydrogen proton so this can readily donate a hydrogen this can readily donate a hydrogen proton so this is is generally viewed as acidic acidic now this this this amino acid over here it also and this is where this name comes from actually the acid comes from this carboxyl group that's the acidic part and then you have an amino group you have an amino group right all right over here and because it's involving nitrogen this is the amino group this is what gives the amino part of the name amino acid amino acid and this is actually generally basic because nitrogen could it has a lone bear it has a it has a lone pair of electrons right over here and so it could use that lone pair to pick up to form a bond with a with a hydrogen ion to pick up a hydrogen ion so under the right circumstances it can form a bond with a hydrogen ion which we know a positive ion which would just be a proton and so it would have a positive charge and so since it can hop up hydrogen ions we can view this as the amino group as being basic but this right over here is leucine it's amino acid super important for muscle growth but there you can appreciate you have essentially a hydrocarbon chain but it has a carboxyl group at this end and an amino group right over here another thing that you'll sometimes people talk about is even hydrocarbon groups for example if you consider the main chain of this and we could consider it either using this carbon or this carbon but if we consider this to be the main chain of carbons if we consider that to be the main chain of carbons then we would consider this right over here to be a methyl group remember the prefix meth refers to one carbon so it's one carbon bonded to a bunch of hydrogen's to three hydrogen's here and so we would call this a methyl group and in general if you have a hydrocarbon bonded to other hydrocarbon groups these things are are hydrophobic so these things there's nothing polar about them and so they're not going to want to at least this part these parts of the molecules are not going to naturally we dissolve inside of water now the last group we're going to focus on you're going to see a lot of these and especially in biology you're going to see it as part of ATP you're going to see this a backbone of DNA and that's phosphate groups and this right over here this right over here is the phosphate group I've drawn it bonded to a bunch of kind of a group over here who knows what it is bunch of carbons a bunch of other things and then I've monitor it to two hydrogen's but it doesn't always have to be bound to hydrogen's but what it is bound to hydrogen's like this is considered to be pro its protonated and so it can actually take up it can actually hog these electrons and dump these hydrogen's and dump these hydrogen's into a solution so a phosphate group is considered to be acidic it is considered as well especially what it is protonated like this it is considered to be acidic because it can donate protons so this is just an overview a lot of the functional groups you will see throughout biology and a lot of big hairy complex molecules when you actually break it down you say okay there's a hydrocarbon chain there I see a sugar there I see a bunch of hydroxyls and I have a carbonyl group oh I see an amine group I see our amino group I see a car Bock carboxyl group you can think about is this going to be acidic is it going to be polar or do different parts of the molecules have different functions
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