okay in addition to the two types of chemical bonds we also have other molecular interactions these are interactions between one loss on another molecule or sometimes between like regions of one molecule on itself these are not too long they are not as strong in terms of their force as to bond so it's not true chemical bonds they're not going to involve the sharing or stealing and giving up of electrons that's the difference let me simplify that by say no electron exchange but recognize we're not always exchanging electrons how about no electron exchange or sharing and again because they're not involving electron exchange or sharing they're not as strong as two chemical bond either I don't have to use chemical means to break up these interactions the way would with chemical bonds but they can be hugely important in terms of biology and the two that I want to talk about and there are more but first is sort of a simplification if you remember van der Waals forces it's a simplification of that and it's going to be hydrophobic interactions and the second type are going to be hydrogen bonds and these are hugely hugely important to biology I can't emphasize that enough in general everything that we cover in this chapter you think oh I don't need that this is you know chemistry it's not biology it keeps coming up again and again and again if you don't get it the first time it really sucks because you keep not getting it so really do your best to grasp it now okay let's look at hydrophobic interactions this is what happens when you put nonpolar molecules in a watery environment like health that's being and living things and hydrogen bonds which don't have to involve hydrogen and aren't sure bonds we can also simplify this is H bond these are internal yqr interactions so interactions between two different molecules that are the result of polar covalent bonds within those molecules and the sometimes these are referred to as velcro interactions they are reversible so we was so sorry to say they are inter molecular so inter ER means between two different molecules is like interstate runs between two different state interactions that are the result of polar covalent bond okay hydrophobic interactions I'm not going to spend a lot of time talking about now because we'll see us again in Chapter three and we'll see this vocabulary again in Chapter three but let's go ahead and do it now hydro means water right if you're hydrated you have enough water in you phobic I think we all probably know what that means arachnophobia for example means fearing spiders here hydrophobic means bearing water and another term the node is hydrophilic silic means the loving like philosophy is a love of learning so hydrophobic are molecules that don't mix with water [Applause] another way to say that is they are fatty right that's our sort of common understanding of them I think about the last time you tried to wash a really away we can and the other way to say that from the term we just learned is non polar on poor so nonpolar when the molecule is nonpolar it is also going to primarily be fatty if there's there some exceptions so this is sort of a simplified way to look at non poor hydrophobic so as you're still struggling with the nonpolar and polar thing and one trick is going up your nonpolar the same is hydrophobic but you kind of you have to make that Association so when I see a lot of carbon hydrogen bonds or carbon-carbon bonds for example in a molecule this tells me that this molecule is not going to mix well with water and you all seen this right so you've seen the little fat globules that sit on top of something that is primarily water based those are those little molecule they actually get kind of shoved to the side by the water molecule and they hang out together get shoved aside the water molecules in a water environment two stomachs and then the inverse of these hydrophobic interactions are these hydrogen bonds and we spend all of the next chapter talking about water which is necessary for all life and its properties and its properties water properties are really the result of these hydrogen bonds right so think velcro so as I said these are not true chemical one and they don't necessarily have to involve hydrogen atoms they often do but they don't have to okay and water is great at farming hiding apart so here's my little water molecule little lines represent shared electrons and there's two right the covalent bond we only see these lines and covalent bonds and because these electrons and more time next to oxygen electrons are negatively charged oxygen ended up having a slight negative charge both I didn't have a slight positive charge but I never have just one water molecule right here's a second water molecule and we know that opposites attract so how is this water molecule going to be attracted to this small water molecule are the oxygens going to be attracted to each other are the hydrogen's going to be attracted to each other remember opposites attract opposites attract so here's my water molecule I put velcro on it we'll talk about these molecular models here in a bit and I think that are helpful way to visualize what's going on because of course we can't really see on them the red always represent oxygen oxygen is going to form two bonds to get its full outer set down plectrums the great things represent the chemical bonds of shared electrons whites are always hydrogen and you see these pictures in your book - and I put a little velcro on it so here's slightly negative oxygen slightly positive hydrogens here's my second water molecule is it attracted here no imagine these are like two north poles of magnet they repel each other instead here's a negative and here's a positive they're attracted to each other like this and they actually velcro together they're not going to stay like that they'll kind of stick together for a bit and then they'll come apart they might end up getting stuck together like this or like this right but it's always the hydrogen of one and the oxygen together because slightly negative slightly positive that's how water molecules interact with each other so hydrogen molecule hydrogen bonds if I were to draw this on paper to get an attraction like this these little train tracks here represent an H bond between opposite partial charges a temporary interaction and it means these water molecules interact with each other it's again they it's because of the polar covalent bonds within a molecule he's poor because the two sides are opposites just as a final thought what if I have a carbon bound to an oxygen let's make sure everybody has a full set so here's here's a little molecule this kind of bigger than anything we've encountered before and we will suspend a chapter talking about carbon is a great building block and it formed four covalent bonds so this oxygen has to hydrogen has one everybody's attached these are all covalent bonds take a second and go through and label the partial charges if they exist right so if there any of these bond any one of these are polar you label the partial charges just like we did here partial negative partial positive and then decide if I have a water molecule if this water molecule going to interact with this molecule and where and how right where am I going to have the opposite charges that allow this molecule to interact with this molecule I touch your final little thought