so Dr Greg here Chris we're going to be talking about chemistry we're going to be doing a little bit of a review of chemistry because we need to understand how different molecules interact to make a living being you know one way to look at a living thing is a bunch of chemical reactions taking place inside of a b body inside of a cell or a bunch of cells as the case may be we call that metabolism we call that biochemistry so we need to understand a little bit of the chemistry that you guys should know by now here we have a molecule you should be familiar with sodium chloride table salt sodium chloride by the fancy name well it's made of one atom of sodium and one atom of chlorine and what you should notice right away is that the properties of sodium and chlorine are much different than the properties of table salt sodium itself is a metal a toxic metal and chlorine all metals are toxic hopefully you guys aren't needing metal sodium which is a metal and chlorine which is a poisonous gas when those atoms interact they give you sodium chloride an ionic compound which is delicious and less toxic than chlorine gas um molecules you understand how molecules are formed when atoms interact um we say that the interaction between the atoms is a chemical bond Bond and most molecules are formed by sharing of electrons between two or more atoms or um the transfer of electrons between two or more atoms so we need to focus on three kinds of bonds for this course namely Co valent bonds hydrogen bonds and ionic bonds so what is a calent bond a calent bond is formed when two atoms share a pair of veence electrons electrons in their outer shell in this example here we have two hydrogen atoms and when they share their electrons we get a molecule of H2 okay and this is called a calent bond Cove valent bonds um you could have two atoms that share more than one pair of electrons all right so if you share one pair of electrons you have a single Bond if you share two pairs of electrons you have a double bond when oxygen see that here when two atoms of oxygen interact they form a double bond okay we're going to see a lot of double Bonds in some of the biochemistry that we're going to be looking at very soon um some of the consequences of the formation of these atoms well here we see up here calent bond between two hydrogen but if we go to another molecule you guys are familiar with H2O H2O water now water is interesting because hydrogen and oxygen they form calent bonds so that's the H2O you're familiar with but what's interesting about oxygen is that it is more electr negative than hydrogen atoms what does that mean it means that the electrons are going to spend more time around the oxygen atom than it will around the hydrogen atoms what does that mean well electrons carry a negative charge so if they're going to spend more time on this end of the molecule here then this end of the molecule is going to be more negative and this end of the molecule is going to be more positive so water ends up being a polar molecule it has a negative end and a positive end and the reason why it's polar is because one end is more electronegative than the others another common um electr negative atom that you'll be seeing in Biochemistry is nitrogen okay we have a lot of nitrogen in our bodies and nitrogen is more electronegative than carbon or hydrogen so it has an electro negative effect as well all right now because water is polar it can form hydrogen bonds with other atoms particularly other sorry other molecules other molecules like other molecules of water for example so h bond forms when the partial negative charge of one oxygen atom in a water molecule interacts with the partial positive charge of hydrogen in an adjacent molecule well what do we call this we call this a hydrogen bond okay again these are usually going to be formed when you have nitrogen or oxygen present with carbon and hydrogen okay um you guys are familiar with the term ions I hope so an ion is a molecule that carries a charge okay and it can be positively charged we call those catons or it could be negatively charged we call those anion and as you know probably from grade one is that Opposites attract a negative charge is going to attract a positive charge and the interaction that results is called an ionic bond sodium chloride is such a bond if you're going to look here you'll see that sodium has a positive charge sorry for that ugly Circle and chlorine has a negative charge so they're going to interact together and what you get sodium chloride table salt which we see down here it's a crystal right would think that's table Sol would you okay compounds could be inorganic or organic okay so inorganic and organic well should probably start with organic organic actually means anything that contains carbon okay so a carbon based molecule is organic it's not like what we hear about you know in grocery stores and on the news um organic just means with with it with carbon and in organic of course are things that do not contain carbon so organic molecules are going to include carbohydrates fats proteins and nucleic acids these are the four molecules we're going to be learning about in the next uh three or four lectures and inorganic uh molecules that are very important to life are going to include water salt and certain acids or bases okay water is the most important inorganic compound in life because a cell is usually going to be 60 to 80% water so why is water so important why have living things um evolved to uh R so much on body so a high heat of vaporization is is very important of course right it means that um it takes a lot of energy before um the temperature of water changes and of course a high amount of energy is required to vaporize it right so we don't vaporize the moment the temperature goes up by a few degrees I hope hope it hasn't happened to you um high heat of vaporization high heat capacity well this relates to homeostasis of course as well right your body needs to maintain a certain constant temperature throughout so because water resists these changes due to changes in temperature um it is um the the solution for most of the chemical reactions that are taking place in your cells are taking place in your body okay hydrophilic and hydrophobic remember these words um they're going to come up a lot something that's hydrophilic water loving means it will dissolve in water readily ionic compounds like salt will dissolve in water this is um um something you're probably familiar with you can go try it out if you don't believe me dissolve some salt in water it's quite easy non-polar molecules are hydrophobic okay you could probably name some hydrophobic compounds lipids lipids include fats and oils What happens when you put oil in water well your oil will kind of flow to the top because it's not going to dissolve in water they're going to aggregate with other non-polar molecules mostly whatever other oil is already there okay very reactive water can be used to cushion and from an ecological point of view it's very important that water floats when it's frozen okay water is an odd compound in so far as it's less dense when it's um Frozen um the molecules form a kind of a crystal lattice they call it which keeps the other water molecules at a particular distance from each other so this crystal structure that's formed this lattice is less dense because the water molecules are all being held at a particular distance from each other so ice floats on water and this is very important for um different types of ecology um that will be studying towards the end of the semester cohesion well water molecules are going to stick together they have a high surface tension so here you see a creepy looking spider well it's kind of cute but maybe you're afraid of spiders but there it is a water Strider um standing on water because it has a high surface tension surely animals like these appreciate that property of water but it's very important for plants the fact that water is very cohesive it means that plants can draw water through their um vascularization a lot easier right so you've seen you've seen plants trees different plants they need to draw water up from the ground draw them up to uh their leaves and their branches that are very high well this is um helped Along by cohesion all right so water you knew water was very important have you ever heard that life on Earth is carbon based carbon based know that carbon is an atom presumably um most of the um molecules in your body are carbon based so when I talk about proteins lipids carbohydrates and nucleic acids these are all carbon based molecules ules okay and all life on Earth is carbon based if you're a science fiction nerd you've probably heard that theoretically silicone based life has been theorized by certain science fiction authors well why is that because silicone and carbon they can form four stable bonds making them very versatile atoms meaning they can form many different types of compounds with many different types of molecules so when we look at carbon's versatility well well here we see one example of how versel carbon could be it's just forming a long chain octane right just a long chain of eight carbons flanked by hydrogen high energy molecule by the way this is why it can be used as a fuel here's glucose well this is also used as a fuel but it's used as a fuel mostly in living organisms okay six glucose molecules this is called a carbohydrate it's flanked by hydrogens and hydroxy we'll learn what those words mean in the next lecture in the next video okay now carbon when we say it's carbon life is carbon based or most of these molecules are carbon based what we mean is we can form a kind of a a skeleton if you will of carbon molecules and you can attach different functional groups onto those skeleton onto this skeleton so what does that mean well different functional groups have different properties from other functional groups okay so here's one functional group we call it an amino group you guys have heard of amino acids amino acids amino acids are the building blocks of proteins all right so all amino acids have an amino group and a carboxy group carboxy group okay these are two different functional groups on a carbon skeleton okay here in your notes you have a list of different functional groups um so what macro molecules do we study um proteins carbohydrates lipids and nucleic acids sorry if I sound like a broken record what I want to explain to you now is the idea that most of these are polymers proteins carbohydrates and nucleic acids they can form polymers well so a polymer what is a polymer okay a polymer is a chain made from repeating molecules repeating molecules which we call monomers so we talked briefly about amino acids correct now an amino acid um is one kind of a molecule that we found in proteins now let's say that these monomers down here in this figure at the bottom let's say each one of these represents an amino acid if we join together different amino acids in a chain well those amino acids those monomers form a polymer and that polymer is what we call a polypeptide okay and the polymer ization of a molecule occurs through reactions that we call condensation reactions why do we call them condensation reactions condensation refers to water so whenever two monomers are joined together the reaction produces one water molecule what if we wanted to break this down well then we would need a hydrolysis reaction try and break this down it looks like a complicated word but Hydro water Lis is a word you're going to see a lot in biology so you may as well learn it now any any anytime you see L Ys or lyt lysis or litic it refers to something that's breaking so hydrolysis means breaking with water if you look down here at the bottom of this diagram well here is a polymer many repeating subunits of a molecule okay here is a water molecule the water molecule is going to interact with this hydrogen bond and break one of the monomers off of the chain okay up here here we're forming a polymer here's one monomer okay here's another monomer at the end of a chain when these molecules react okay you see here ho o they form one water molecule and the chain has just been lengthen plus one we're going to see that a little more when we go on to proteins later on so we'll take a little break I'll see you in part two of the lecture we will look at carbohydrate it's