hello chapter 2 The Chemical foundation of life this is a big one there's a lot covered in here um depending on your Chemistry background might depend how easily you grasp this stuff I will try to explain it best I can I take my time um so this is a will probably be a bit of a long one uh so give yourself time or do it in spurts and uh feel free to bring questions to lab or email me or come see me during office hours if you have any confusion or issues let's start with matter you matter I matter everything matters cuz it's all made of matter right all life is composed of matter um matter has mass it's made of atoms this is what I think of it and the air has atoms in it that you're breathing right um occupy space anything you can touch uh feel those all have matter and even things you can't touch right you're not you don't think you're touching the air but there are lots of elements in the Air elements are made up of atoms um with as we'll get to specific number of protons um so the unique form of matter these atoms with specific chemical properties and physical properties um and that uh essentially is based around how many protons they have which results in how many electrons they have uh which can cause it to essentially gain or lose electrons and we will get to that so um think of matter is made of atoms uh atoms make up matter and determine chemical and physical properties which we'll get to some of that elements of course are made of atoms um and they're determined by the number of protons which I'll talk about protons and electrons um and each element is designated by a chemical symbol so they all have a name and then we give it a shorthand symbol one or two letters um to abbreviate it so like things you might be familiar with are hydrogen which is very common in living things so the last slide and a future slide we'll have oh and here I have it at the bottom important to know the four most common elements of living organisms um hydrogen is one of them carbon over here nitrogen and oxygen um and it is somewhat important that they're kind of at the top of the table that means something uh which I'll talk about more later and those are the four we call it Chan c h n you'll often see that cha as the four most uh common elements in living things okay so what makes up an atom that's what I was getting at um they're the atom is made up of subatomic particles so essentially smaller parts but um atoms and atom is what's considered the smallest unit of matter because you essentially have to have these parts um to make the atom so there's two regions um a nucleus in the center and an outer region um that kind of has electrons moving around it so these are two different depictions of atoms so the nucleus is in the center that's represented by the pinky plus and the brown with no charge and that's the same over here um the nucleus contains protons which are these subatomic particles that have the plus this is because protons we say have a positive charge they have a charge associated with them neutrons the brown thing there do not have a charge associated with them but they do add weight um and Mass to the atom because they are practically not quite but very close essentially for the purposes of this class um equal in weight to a proton protons have weight and mass um and are found in the center of an atom with potentially neutrons the number of neutrons can vary in an element which we will get to the number of protons in an element does not vary because that is what determines the element hydrogen has one proton helium has two protons and that is that element if for some reason helium degraded and lost a proton uh which it does not do regularly but can happen in time um it would then become hydrogen it is a different element so uh for the most part protons stay in the nucleus and um are found there then around the outside we have electrons so this is shown by these two negatively charged subatomic particles and they're shown very small all these are very small protons electrons neutrons are all very small but electrons are almost negligible in weight um don't want to say they don't have any masks right they make up an atom which makes up matter but it is very tiny all all the electrons in your whole body weigh about as much of as an eyelash so in any given atom the electron has almost negligible weight um in this the left depiction the electrons are shown um as a cloud around because the thing about electrons is they are always in motion moving very rapidly around the nucleus so atoms in general are is a motion these protons are also like vibrating but protons don't um leave an element electrons can leave electrons are just these like constant motion around the nucleus um and can leave actually the uh element and essentially maybe go join another element which we will get at in a minute so this is showing this left depiction is showing how the electrons really make a cloud around the nucleus being in motion and this is just showing how many there are so if there's two protons there's two electrons that can vary which we'll get to in a minute but in this case of helium it would stay like this and hopefully you'll understand why by the end of this lecture um so again this is mostly repeating what I just said um the proton has a positive charge the electron has a negative charge neutron has no charge but adding to the weight of an atom this Mass which the dubbing Amu um I'm used to calling it dotons um but they're essentially equivalent you don't have to worry about the units of mass for an atom we don't get into that too much but um protons and neutrons are roughly equal technically they're like one point something something something one point something something something I think I can't remember one is actually one and the other one is 1 point something something something they're slightly different but very close so uh again for the purpose of this class we say that prot protons and neutrons um Carry equal mass and we'll see what that means um to the element in a minute and then like of course where they're found the protons and neutrons are found in the nucleus the electrons are found in the orbitals in this motion around the nucleus and again it's a helium atom because we have two protons okay so the periodic table organizes our elements periodically because they behave in certain manners which I'll get to more as I go through this lecture um but when you look at the periodic table at the top usually this is shown above the element in some way is a number this represents that number on the periodic table and how many protons it has it's it's atomic number because that determines the element how many protons it has so hydrogen has one helium has two lithium has three so on on so on I want to go over here and look at um our ones right we said that hydrogen carbon nitrogen and oxygen are common so carbon has six nitrogen has seven and oxygen has eight so our common ones hydrogen 1 carbon six nitrogen 7 oxygen 8 um are relatively small on the periodic table um and so life living things use these elements the most we also have um some fos first that's going to be important when we get to our macro molecules and then we have other elements as well right we we do have some meesum we have potassium we use we have um where's Calcium on here or calcium over here is something we use as well that's important um so there's other ones we use in much small smaller amounts or it's found less although they are still very important to our reactions in our body okay this is a little harder to see on here but the atomic mass is how many protons plus neutrons so now this is the weight of the element um so hydrogen has one proton that also means I should note here when we're talking about a neutral element it's um not its most natural form but like the basic form of just an element if it's neutral uh it has the same number of protons and electrons so if hydrogen has one proton we then assume it has one electron um helium right has two protons so it has two electrons now the weight is the atomic mass that remember electrons don't really contribute to mass so we're looking at protons and neutrons here and this is the atomic weight is written typically under oh I did not mean to go through that typically written underneath the um element although I will say sometimes different periodic tables are sometimes shown so if you see that number 1 point something something if it's just we know it has one proton and those units were one a proton is one unit so if its atomic weight is one then that indicates hydrogen doesn't have neutrons at least in its most common form I will tell you and we'll get to in a minute elements um the same element can have different number of neutrons so there are hydrogens that has an atomic weight of two which indicates that it has one proton and one Neutron because the neutron has now added the weight another weight of one um but that's not the most common form the most common form would be this one which only has one so it only has one proton and no neutrons over here if you look at Helium helium has an atomic weight of four it's a little hard to see but it has atomic weight of four it does show if that's a decimal point after the four um again that's the small value um because it's not exactly one but for our purposes we can round up or down whether it's 0.9 or something just look at the whole number so if it's four we know helium has two protons so if its atomic weight is four and it has two protons how many neutrons would it have because atomic weight is protons plus neutrons well you could do the algebra um you could probably figure that out as well in your head that there must have two neutrons so helium's most stable or most common form I should say has two protons and two neutrons in its nucleus so that's the way you figure out um if you're given the weight and the atomic number you can always or I should say if you're given the atomic number and the atomic mass you can figure out um the number of neutrons in an in the element the periodic table like I said usually does the most common form of the element um but others are found we'll see more of that in a minute all right so I talked here I've zoomed in on uh this one talked about how elements can have different number of neutrons and there is a name for that when an element an element this is important for later things we're going to learn about when an element has different number of neutrons that's an isotope Isotopes are when elements have different number of neutrons so it's still the same element it has the same number of protons but its neutrons can change which changes the weight um so I mentioned hydrogen um and hydrogen can have different number of uh neutrons in it carbon is a common one you've probably heard about and will come up in your book and and come up in times carbon 12 is the most common form of carbon so it has six protons but its atomic mass is 12 so what does that tell us about how many neutrons it has I hope you know six that means it typically has six protons and then six neutrons in its nucleus and that gives an atomic weight of 12 but car you may have heard of like carbon dating well carbon has other isotopes that we see carbon 13 which has six protons but um seven neutrons and 6 + 7 is 13 so carbon 13 is when the carbon's atomic mass is 13 it has seven neutrons and carbon 14 has six protons and um eight neutrons so um these are different isotopes of carbon which I actually think I have another slide on and then here's that slide I got ahead of myself so you can see that here all right Isotopes like I said have different mass and because they have this different mass that can make them behave slightly differently so heavier elements and heavier Isotopes meaning the more neutrons found Decay faster than lighter smaller one so earlier I said there's a reason why the most common elements in living things those four most common elements Tron carbon hydrogen oxygen nitrogen are tend when you look at the periodic table as a whole are on the smaller side now like nitrogen and and uh oxygen being seven and eight aren't exactly tiny I mean all elements are tiny but themselves aren't tiny when you compare it to like hydrogen which just one hydrogen is very small so they're still right oxygen is eight times bigger than hydrogen but when we look get all the elements on Earth um they're definitely more the smaller ones and part of that is larger elements don't last as long they're heavier when they have all those protons in their nucleus and particularly when they have protons and neutrons in their nucleus that makes a very heavy nucleus that um is essentially pushing away so there's a reason we say positive um we call protons positive and electrons negative because they have these charges they uh Opposites Attract in ATS and and elements positives are attracted to negative and also um likes repel so positives will repels and negatives will repel so when you have all these protons in a nucleus they are held together in chemical forces but the heavier the more protons there and like I said The more neutrons the heavier it is and the faster it decays essentially it comes apart so we don't see those larger if you look at the periodic tables we have some that get into to the hundreds like what lower hundreds hundreds you know into the 9s up into the we have a low hundreds um those elements um are shortlived like very shortlived it could be fractions of seconds um some of them we've only done experimentally by like forcing practically forcing together crashing together um elements of smaller sizes to to try to get them to fuse um and we can and they'll like last for fractions of a second and then be blown apart again because they're so heavy um so the super large elements really aren't found in um Earth at very large amounts at all um some of the smaller ones are and living things are made of these smaller ones part of the reason um and so the heavier the more so here's hydrogen right different hydrogen um Isotopes the heavier Ones Will Decay faster than the smaller ones and again the periodic table shows the most common isotope found uh that we know of typically at the time I will say sometimes you'll see older PCT taes and sometimes their atomic masses different than newer ones because we've um we've realized that some are more common than what we thought or less common um so you can see Chang in periodic tables over time the previous video might be helpful to watch for you to understand um so I left it in there but you can just follow the link if you're interested in watching that um Isotopes I kind of mentioned carbon dating before Isotopes are used to date um things we find not just fossils but uh other ancient things as well um fossils living things or things that were living we used various dating um because of the elements known in it and the ratios and what um essentially how many how common an isotope is and we know its rate of Decay essentially when carbon 14 decays to carbon 13 or carbon 12 or nitrogen 14 as it shows on here um these different amounts of Decay we can use the ratios they have how much they have of it in to get an estimate of how old something is um so various Isotopes are used I don't need you to know the details of this it's been the scope with the class but this is going to be important I want you to know it vaguely for this unit and then it's going to come back up again a little bit when we um talk about fossil evidence for evolution towards the end of the semester um but different isotopes are used we hear of carbon dating but that's certainly not the only one right we have uranium here is another common one um and there are others um that are used and it helps give us more accurate pictures right the different elements we have um and some we know like how long they take to Decay and so like really old things when we're going into the millions of further millions of years right um then see how this is less this is5 50,000 carbon um isn't great for like the really old things Uranium on the other hand is Maybe better for some of the older stuff um so different elements in Isotopes are used uh in looking at the ratio to when we're thinking about how old this is uh and you know right if they have very little of something we can say oh it's got to be past this cuz this is already decayed um and we have other ways of dating actually when we sequence DNA which maybe we'll get to later there's ways of dating um using DNA and so it's nice when we look at old stuff if we can get DNA from it some of the really old fossils of course we can't but um when our DNA estimates uh line up with uh other ways of dating fossils um it's a good another line of evidence to support that that is the age we're estimating it to be I also want to note here it's not specific right it's not like it is exactly 1 million uh 150,00 years old it's typically a range it's like oh it's uh you know 900,000 to uh 1.5 million years old or the older you get it might be more like oh that's like between 150 and 200 million years old um right we have a range you can't like get it down to the second or even the year but we can get a age estimate range I should say electron shells okay this is very important and from here out I hope you take some time to understand um what this is so there are different ways of depicting atoms and elements the this one shown here with kind of showing the nucleus and the element as the nucleus and then their protons around it in these shells which we'll talk about in a minute it's called the bore model I don't need you to like know fully there's a bore model I just want you to be aware that this is the bore model and there's other ways of depicting elements as well um your book kind of goes into them I'm not going into them because I'm most concerned that you understand this one um the bore model is not showing um exactly how the electron is which we can't even show electrons are in literally constant motion around the U nucleus so like pinpointing it is um not something we can really depict in a picture uh and there's different ways of motion the but the this model our bore model that I use shows which energy level the electron is in and that's what I want you to know and kind of what that means and what we call the octet rule so I'm only going to show you this but just be aware that the the book goes into more of orbital displays and other types of models I'm not too worried I don't you don't need to know those you really just need to know this one for this class chemistry you might need to know more probably um okay so atoms with a neutral charge when you see them at the periodic table they're like assumed to be neutral they have the same number of protons and electrons so however many protons it has we would say it has that many electrons helium has one proton so it has one electron um right so to start with we'll see how this changes but when we look at a periodic table the number of electrons also equals the atomic number because when we're looking at that we're saying they're equal well the thing is electrons and I do want you to think of it like this electrons have energy right we carry electricity to our house there's a reason it's called electricity because it has to do with electrons and in our body um we use electrons to power things as well um essentially the glucose a sugar and the food you eat among other you can actually get it from other things as well um the electrons are harvested from that taken from the food you eat to power to generate a type of energy in your cell which we will get into next unit so I do want you to think of electrons as energy they're um essentially uh yes a way we use energy um where what energy level it is kind of depends how much energy it has so um electrons and what we call the first energy level have the lowest energy and as they move in these energy levels um away from the nucleus they absorb energy and have higher energy but they'll always start in what we call the first energy level and then we call the outer shell something we call a veilance shell the energy levels depend on how big like how many energy levels a element has depends on how many protons it has essentially how big it is um so the way it works is the first energy level which they're saying as one n which is always where we start and our electrons will start to fill first can hold up to two electrons so hydrogen has one proton so it only has one electron so it's first electron it only has one electron in that first orbital if you remember helium helium had two protons so it would have its two electrons also in the first energy level but after that now we're going up to lithium which is shown um in this first one here the LI lithium has three protons so that means it has three electrons well the first energy level can only have two so that means the next electron is going to go to the 2 and the next energy level and here's what we call the octet rule this after the first energy level all the subsequent energy levels can hold up to eight electrons um I'm just going to say somewhat on a side here that is a bit of a lie there are um energy levels that can hold more than eight um but a few things it's one a multiple of eight typically a multiple of eight that it can hold so um right it's like the first one holds two second one holds eight third ones holds eight um a fourth one might hold like 16 so that is a multiple of eight the thing with Biology is we don't typically get that big in our elements if we're getting an element that big in US It's probably causing damage and killing us uh that's not something we use a lot so for the purposes of this class we just say multiple of eights because we're not dealing with elements that large that have it but I do want you to know um that these energy levels some of the large ones and the large elements can hold more than eight but it is a multiple of eight and we just go by the octet rule in biology because that's what we're dealing with so after the first energy level can hold two all other energy levels can hold eight so with lithium you notice I said it had three protons so has three electrons so two are filling the first one and one's filling the outer one carbon remember carbon had six I don't know if you remember but I pointed out carbon's really important so I do want you to pay attention to carbon carbon has six protons so it has six electrons so it's got two filling its first shell and then it's going to have four filling the next Shell right and that adds up to six Florine must have um 2 4 six seven Florine here must have um what do we got 2 4 6 7 plus 2 is nine nine protons so it has nine protons it's got two in its first shell and then seven in its outer shell and it's just missing that last one and then I want you to notice neon and this is really important so neon well really important to chemistry not as important to biology but neon um has eight protons so it has eight electrons two in its outer shell and then 2 4 6 8 and it's outer shell what we call veence electrons or veence shells it's outer shell is full its electrons are full this makes an element happy elements want their outer shell to be full they want um two or none in that first shell and then in every other shell after it they want it to be eight or they don't want it like lithium probably doesn't want this outer electron CU it wants just its veence electrons of two to be full they like to be full and that is what our noble gases are you may have heard the noble gases they're the ones on the far right column of a periodic table they are stable they do not react with things because their veence electrons are full they are stable as a gas at our atmosphere in most temperatures in our in on Earth and they don't react with other things and they don't react because their electrons their outer shell is full and helium is like that helium I said has two protons and two electrons so its litter outer shell is full so helium is above neon on the periodic table and it's happy and then here's just going the next row out it works the same way um they're filling up and so some might just have one on the outer side some can have four and then here when we're in our noble gases it fills the outer one this is an important concept to get so um take your time in understanding this this is going over what I just said but I like the way it shows it's kind of like a pair down of the periodic table it's not the whole thing we're missing a lot of elements in here but group 18 those are that's that far right column on the periodic table they all have their outer shell their veence shell veence shell full the veence electrons in the veence Shell are full and so this group is happy and content and doesn't react um the ones on the far left of the periodic table group one always essentially for the most part um always just have one electron in their veent shell and so there's certain things that they do that how they behave similarly which is why they're put in that column why they're why the periodic table is shown like that U because it's the way the electrons essentially behave um a group essentially a column typically will have the same number of veence electrons in their veence shell which causes them to kind of behave similarly in that column um even though their sizes are different they get heavier as you go down um so uh that's kind of that's why we call the periodic table periodic it they behave periodically in a sort of standard Ood way now it gets a little bit different when they get bigger and why you have those Metals in the middle um um but with biological stuff we're usually dealing stuff high on the periodic table that are lighter in weight all right so why am I harping on about veence electrons and taking so much time because veence electrons determine how essentially the atom or element is going to react with others and that means how it's going to bond which is really important to life or how it's going to behave and um while we don't do too much chemistry in this class just this this uh chapter and next chapter they are very important for everything else how all the cell processes happen and react really comes down to chemistry and so kind of having this basic understanding is important so what does this mean so sodium that was one right it has 281 so it's got 11 it must have 11 protons and then it's got two they're showing them a little bit different here two protons and that first shell and then it's got 8 2 4 6 8 in its second shell and then it's got one in its outer shell so this is in that that group one the column one that has hydrogen and um was it lithium and sodium I think that's the order they go down sodium by the way is it's abbreviation is na um so what if that mean well essentially all of those in that group do the same thing they very easily lose this electron essentially it's often it's easily pulled away and lost if anything any positive charges nearby that thing is gone and um that electron goes away and if that electron goes away now the sodium element has 11 protons but it only has 10 two in the first shell eight in the outer shell 10 electrons it's happy because it feels more stable because its veence electrons or veence shell I should say is full and it's a lot easier to lose an electron one electron than to gain another seven electrons to fill that outer sh right F picking up eight electrons would be pretty hard for this so it very easily loses that electron but now remember electrons have a one NE each electron is a negative charge and each proton is a positive charge so now that it has 11 protons and 10 electrons it has one more proton than electron so now it has a one positive charge a plus one charge this is what we call an ion because it has a charge if something has gained or lost electrons it is an ion and depending on how many electrons it has gained or lost depending on how many charges it had if for some reason sodium lost another electron it would have a 2+ charge um it doesn't like to do that because it's outer its veent shell is full so it's not going to do that but some um Can the next the element next to sodium that has 12 which I cannot think of what it is right now and I don't have periodic table in front of me but if you would imagine um with 12 protons that element would have had two electrons in its outer shell so it would lose two and it would be two plus to be happy um when uh and this I don't know if this is in your book I don't it was in the notes and I didn't see it in the chapter when I was looking through but um something to note is that when an electron has gained I'm sorry excuse me an element an an element becomes an ion by gaining one or more electron that is then a negative ion and a negative ion is called an anion and then when an element has lost one or more electron which makes it positive a positive ion is called a cat ion so ion is a generic terms and then we have two more specific terms cat ion for positive and you think of cats have Paw and are positive my cat paw there looks terrible um so catons are positive and anion are negative so electrons determine how atoms interact does veence electrons essentially are they going to give up an electron are they going to take an electron the other end of the periodic table right before the noble gases right those are on the opposite end they easier they're L missing just like one or two electrons in their outer shell and so they pick up electrons and become negatively charged That's What chlorine does which we'll talk about in a minute um so that's again periodically how they behave um and their and their weight affects how they behave too so these they react with other chemicals um who like may be exchanging electrons picking up and uh picking electrons giving up electrons making bonds which we'll talk about different types of bonds used in biology in a minute and so we have these chemical reactions when different elements and molecules and compounds react with other ones um so a chemical reaction uh one is essentially changing the distribution of electrons but the elements themselves the atoms can be reorganized you you can't gain or lose matter so you have the same amount of of every type of element that you start with when you end but it can be bonded in different ways to different things so this here depicts a chemical reaction reactants are what you start with reactant is what you start with and it's going to be important um a little bit more so next unit but you know and products are what you end with so H2O2 is hydrogen oxide hydrogen peroxide there are enzymes that can break it down in your body because you actually make hydrogen peroxide as a reaction in your body um and light as well if you ever got hydrogen peroxide to like clean a wound it's in a dark bottle because light will degrade hydrogen peroxide to water that's what H2O is and oxygen gas what O2 is um but if you notied there's H2O2 there's two hydrogens and two oxy and H2O2 If this just became H2O and O2 gas there's two hydrogens here and there's two hydrogen here but there's two Hydro oxygen here and there's one oxygen here and two oxygen here so that doesn't add up and that's why there's this number is how many of that molecule or compound you have that you start and end with and this is called a balanced equation I'm not going to worry about balancing equations in this class class you should do that in chemistry and most of you are going to be required to take that um but if you look at it it's two so now you're timesing there's two whole hydrogen peroxide molecules let me erase that little bottom part there's two whole hydrogen peroxide molecues so I just times which means I'm timesing 2times the two hydrogens so there tells me I actually have four hydrogens to start with and then I have two of those as well so I have four oxygen so I need to have four hydrogens and four oxygens on the other side so that should yield me two water molecules which that is four hydrogens and then the two * the one oxygen here is two but I have two more oxygen here so I do have two oxygens and I'm sorry not two I have four I have two plus I have my 2 plus 2 of my oxygen so I have four oxygens and four hydrogens so I do have a balanced equation now again I don't need you to worry too much about balancing but if you're in chemistry and you're struggling with it I just thought I should go over that we do we should have balanced equations but we don't always show chemical reactions as balanced um but that's like two hydrogen peroxide molecules will yield this arrow means yeld or make two water molecules and one oxygen gas molecule and the arrows are important so if the arrow is only going one way then that means the reaction only goes one way it's irreversible that's um that hydrogen peroxide yields water and oxygen and they are not going to react back to make hydren peroxide some reactions are reversible is in that they can go either way and they go back and forth essentially on your own and this like this reaction down here happens in your blood and in our sea waterer and um other things um but the the the reaction can go back and forth um and some will happen so reactants are into products and then the products can become essentially the reactants to make this the product later so they're they get converted back to reactant almost all of that particularly the veence electrons part is to lead up to bonding and and this is really important understanding bonding and if you understand the veence electron stuff going on you're going to understand this bonding better so for biology there are three types of bond you need to know there there are other bonds out there particularly metallic bonds is what you probably learn if you're taking chemistry but we don't deal with those these are the the very the three very important ones for biology um and what you you definitely need to know for this class because you're going to have to learn them um when they're used where they're used and particularly different types of calent bonds so I have a slide on each of these so you don't need to spend a whole lot of time here um but I just want to say the three and then I'm going to go over what each of them are how they're formed so Cove valent Bond um is one we're sharing electrons we'll come back to that um ionic bonds that's ions two oppositely charged ions bonding and then a hydrogen bond is a very strong attraction it says weak electrical attraction um because it's an attraction more than a bond but it's strong enough attraction that we call it a weak Bond um so we'll go over each of these separately calent bond is the most important one to know and it is um when electrons are shared so when two or more electrons are shared between one or more element so this can be just one element you noticed uh earlier I said oxygen gas as a molecule that is because it shares electrons to make that O2 um in living things calent bonds are very strong it's a little bit different in chemistry um because bonds are affected whether they're in water or not in so biology um our strength of our bonds is a little bit different um so water something you're probably very familiar with and You' probably heard of as H2 2 it's two hydrogens and one oxygen is made by sharing electrons so oxygen is uh 8 doesn't two four six doesn't show it here but it'll have two electrons on its first one and then it has six on its outer shell so it has two which it um wants then a way to either fill this outer shell either gain two electrons or share two electrons with it hydrogen has one it often very easily loses that one and becomes a hydrogen ion which is H+ but it can easily share it because it would want to to fill it out shell so what oxygen does is it will bond with two different hydrogens and now that hydrogen electron helps fill its outer shell where it's got eight in its outer shell cuz here it would be seven and then it bonds with this other hydrogen which makes eight so now it's outer shell is full it's veent shell is full it feels great hydrogen its outer shell is full and has two so it can feel good um we're going to come back to water because it doesn't stay exactly like this but this is where H2O comes from and that's a calent bond because they're sharing electrons so these electrons are in motion all around the molecule um a molecule is formed by um elements that make calent bonds so anything that has a coent bond is a molecule so water is a molecule um O2 gas oxygen gas is a molecule because it's two oxygens making coent bonds uh so let's I got more on calent Bonds in the next slide as well I thought I might have had oxygen gas right so um a single calent Bond or was just when two electrons are shared so that's in the case of H2O that's a single coent Bond there's always two electrons at least two being shared um oxygen gas it's actually sharing like four electrons so it's outter shell right at six it's making this what we call a double calent bond there's it's sharing four electrons these all are four and they are held together strongly the electrons moving around the two oxygen um nucleus that are held together so this is a double calent bond that's even stronger so like oxygen gas is held together stronger than um a water molecule because water molecule only has a single the two hydrogens with oxygen is only a single coent Bond nitren gas N2 has a triple coent bond I don't think I have an image of it here but you're welcome to look it up um it would be sharing six electrons and so that's a very the nitrogen gas is a strongly held gas then um N2 right that's a very strong molecule so um the more calent bonding the stronger it is um but in general in biology a calent bond is strong but do whether it's a double or triple is stronger than a single calent Bond now the very very important part which you again need to understand so spend some time on the slide if you don't get it there are in general what we call two types of coent bonds we say polar calent bonds and non-polar calent bonds polar calent bonds is when the electrons are unequally shared or we say electrons are unequally distributed around the molecule so let's look at water a very classic polar molecule that of course is very important to life on Earth which we will get to and part of a huge reason uh why it's so important is its polarity so I said earlier you have your oxygen right that is sharing two electrons one with each hydrogen to fill its outer show remember earlier I said while our four common elements in living things are small oxygen is much bigger than hydrogen right oxygen has eight protons in its nucleus hydrogen has a one so when these electrons are in motion around the water molecule where are those electrons going to hang out more I hope you're thinking the oxygen oxygen is what we call Electro negative it's highly Electro negative meaning it pulls electrons towards it and again if you think about it it's got eight eight protons here in its nucleus while hydrogen has one so when these electrons are in motion they're really going to be spending they're in constant motion around the molecule right it's really making a cloud around the molecule but they're going to spend more time around the oxygen as they're moving around they're just more often going to be found around the oxygen than the hydrogen this means that there's a partial charge and this is something I want you to get at there is no overall charge to to have a charge for something to have an actual charge a plus or minus or two plus or two minus charge it has to have gained or lose lost electrons electrons were not gained or lost in a water molecule there is the same number of electrons moving around them as there are protons right there are 10 protons two in hydrogen and eight in oxygen and there are 10 electrons moving around them so there is no overarching charge but the electrons do hang around the oxygen more and this causes oxygen to what we say is a partial that's what my squiggly line is which actually has a Lambda symbol you'll see on future slides a partial negative charge and because the electrons are hanging on oxygen the hydrogens are exposed and they have what we call is a partial positive charge because the electrons aren't around them as much not making them neutral they have a partial positive as in their protons you know putting out some positive attraction there so this is polar it's polar think of Polar Opposites because the molecule itself has opposite charge one side has negative charges partial negative let me be clear partial no overall and the other side has partial positive they are opposite so it is polar oxygen is electr netive pulling the electrons towards it take some time to know about that because polarity is very important and water's polarity is very important to life so water is polar and that will come up again and again on the other hand in our coal bonds sometimes the electrons are equally distributed around the molecule when they are equally distributed it is said they are nonpolar electrons are equally shared so so here let's look up at this little table here we're showing water a water molecule has oxygen sharing electrons with hydrogen the electrons hang out on oxygen side and so that's what that little squiggly look looks almost like an eight here is a Lambda signal that means partial there's a partial negative there's really two partial negatives we'll see in a little bit on oxygen and there's a partial positive on hydrogen on the other hand meth is CH4 it's a carbon with four Hydra it shares remember carbon I don't know if you remember but it has four um veence electrons we're going to come back to that in a little bit um so it likes to make four bonds so it bonds with four hydrogens well they are all equally distributed around like the way the hydrogens are around the um distributed around the carbon the electrons are in constant motion equally around that so it doesn't there's not directionality there's not a positive end and a negative end so methane is non-polar nonpolar and polar don't really mix well it's and I it's really I used to kind of think it about as non-polar just doesn't like to react with stuff but what I've realized is that polar things really just don't like non-polar stuff because polar has partial charges it likes to be attracted to something either with another partial charge or a charge where the partial positive can be attracted to something that's negative or partial negative and the partial negative end wants to be attracted to something positive or partial positive and so when stuff is when non-polar stuff is in polar stuff the polar doesn't like it because it can't react with it so it kind of just pushes it away really like a bully I I now look at water as a bully I still love it but it's a bit of a bully so oil and water don't mix oil which is a fat we'll get to next chapter um is non-polar completely non-polar for the most part sometimes we get some water in there but um oil doesn't mix and so that's why when you put oil in water you see it clumping in all those like bubbles which is actually shown as a very pretty image here on the right um doesn't dissolve in it right it it just gets kind of pushed together by water cuz water doesn't like it and that that is called hydrophobic interactions when that the bully of water which is po polar pushes the non-polar molecules together to kind of keep it away from it because it doesn't want to it wants to react with stuff and it can't react with that Cove valent bonds are sharing electrons super important we'll come up again and again we'll we'll see that throughout the semester so make sure you get your calent bonds because in the future you're going to have to learn different types of calent bonds um ionic bonds are also important in biology and this is when you have ions bonding cat ions and an ion bonding so we talked about sodium earlier likes to lose an electron um yes electron cuz it just has one in that outer shell and so to be happy it likes to lose it um chlorine is uh on the opposite end where it's one short in its veence shell so it likes to pick it up so sodium and chlorine sodium becomes positive and chlorine becomes negative because it's picked up an electron and they have attraction to each other this this little depiction here isn't great because it's showing them as the same size which they're not um I can't remember now which but one of them is a bit larger than the other one uh is it the sodium I can't remember which one now but one of them is a bit larger than the other so they're I don't like that they're showing them like they're equal sizes because they're not but sodium and Chlor you have a positive sodium and a negative chlorine and then they are attracted as two ions right because this is a cat I sodium and an annion chlorine are attracted to each other to make an ionic bond this is very strong chemically um that force that positive attraction to the negative like or the the positive remember I said Opposites Attract positive negative um that's very strong chemically in a strong strong force that holds them together and this is where biology is a little bit different you'll see in a minute ionic bonds uh in chemistry you'll probably learn that ionic bonds are very strong and stronger than coent but in in biology ionic bonds aren't as strong in water and you'll see why in a minute so they're not considered as strong because they kind of come apart easier uh in water um and so and coent bonds don't come apart in water so coent is really kind of the more important stronger they're all important to biology but coin is really the stronger bond in biology because what's happening in water but the force itself I should say is stronger it's just that water can overcome this in some cases which we'll see in a minute uh and by the way sodium chloride n NAC is table salt this is the salt that if you um add to your food for the most part is usually table salt na ACL uh side note here your book I don't know how much your book goes into it but compound s are made up of two or more elements molecules can be one or more elements but are made by a coent bond so like sodium chloride is a compound but not a molecule because it's not made up of a calent bond um but it's made up of two or more elements water is both a compound and a molecule because it is H2O oxygen gas is a molecule because it's made of a coent bond but it's not a compound because it's only made of one element so those are some terms just to help you um I you we'll use molecules a lot and I just want you to remember that molecules are calent bonds that's going to be important our last one/ two bond is really the hydrum bonds um so let me start with Vander walls interactions Vander walls interactions are weak attractions between two or more molecules that kind of have these um different ends if there's some if there's a positive in a molecule and a negative the there's an attraction um between each other that kind of can pull them towards each other but Vander walls interactions aren't really a bond cuz it's it's more of an attraction where they're pulled but they can very easily break and be pulled apart um but when it's hydrogen that is attracted when it's hydrogen which is um in our cases always going to be for in a molecule if it's in a po polar calent bond it will have a partial positive when it's attracted to an oxygen or nitrogen which will have a partial negative um we call that a hydrogen bond and that is stronger than a Vander walls interaction so hydrogen bonds we do consider Bonds in biology they're really a strong type of Attraction which is why it's called a weaker Bond it is um what it really is is a strong Vander walls interaction but but um it's strong enough to be considered a bond while Vander wals we don't consider a bond we don't worry I'm not going to go too much into Vander wals in here because um that can happen between molecules and can affect bonding of um proteins and things or amino acids I should say but um hydrogen bonds are very important in life because of water we'll make hydrogen bonds with other water molecule um because of the way our our molecules what we call macro molecules which are large molecules we use in our body some of that hydrogen bonds are important to it hydrogen bonds are very important in life so I want you to understand hydrogen bonds more um and hydrogen bonding so a water molecule this is important a water molecule is held together by a Cove valent Bond right the two hydrogens are sharing electrons with one oxygen but water molecules plural are held together by hydrogen bonds so remember they have that partial charge so a hydrogen has a partial positive that's the Lambda which I'm not going to draw and the oxygen has a partial negative and they're attracted to each other through a hydrogen bond and this is what causes water to stick to other water this is what makes liquid water and we'll see water is a good solvant um so I want to note that oxygen has two partial negatives essentially the oxygen end of a water molecule can bond with two hydrogens hydrogen bond with two hydrogens of other water molecules and each hydrogen itself can also bond with um an oxygen so one water molecule can make up to four hydrogen bonds sometimes I ask that on the test so I like you to know um that a single water molecule can make up to four hydrogen bonds um the other thing I want to note is how these bonds are displayed this is pretty Universal um a calent bond is typically shown by a solid line and a hydrogen bond is shown by a dotted or dash line so it's a good way to tell whether it's uh Cove valent or hydron Bond right the water molecules are being bonded together by this dashed line so you know it's hydrogen bonding while the the water molecule itself has a solid line so it's Cove valent bonding usually if this was a lecture I'd break here and so like this would be done on a different day so if you want to take a break and you know think about what I've gone over feel free this kind of switch gears a little bit now we're going to talk about why water is so important um so it's kind of the second part um of chapter 2 um so water super important makes up close to 70% of um a human body uh right makes up up most of the earth um to some extent I should say not when you look at everything but um life evolved in water um it is important for life it is needed for life but why is it so essential because it is polar and being polar allows it to form hydrogen bonds that makes it really important and we're going to look at these different what we are what are often called properties of water or um characteristic of water that are important for life this is all I went over I just want to make sure you know it this is why water right water is polar because the oxygen is electronegative giving the oxygen end a partial negative charge and the hydrogen's a partial positive that allows water to bond with other water molecules and other things which you will see and they make hydrogen bonds with these and that's going to be important we'll see here in a minute these hydrogen bonds um actually change in stability and a bit in how water is shaped depending on temperature so liquid water right which you think of as water um is H2O being together in its calent Bond and then making hydrogen bonds with other water molecules well water usually isn't uh fully bonded to all other water molecues so in this example here that one in the middle is making four hydrogen bonds that's actually not very common in water and water the water molecule is making like two to three it they're constantly breaking and reforming because one there's often other stuff in water that they're being attracted to and they're attracted to other water and water disassociates which we'll get to in a minute so what's really happening is a water molecule is constantly breaking forming hydrogen bonds so at any given time a water molecule is bonded to 1 2 3 maybe four other water molecules but usually kind of the two or three so it's the hydrum bonds are being broken reformed and the water molecules are moving right it's uh moving pretty rapidly as elements atoms are always in motion molecules are always in motion as well and part of that motion is just naturally breaking and reforming these hydrogen bonds so it's in liquid water in the gas State not shown here the hydrogen bonds are B breaking uh the calent bond isn't usually breaking unless if you're getting really hot um but right when you're boiling your water your liquid water is breaking these hydrogen bonds but your water molecule is staying the same you have water that's that steam above your pot is water vapor and that's the um water molecule itself going into a gas State now in this state it can make uh it might be making loose um bonds right it still might make a hydrogen bond with another water molecule but it's not going to be in the it's not going to have bond with all four of them uh and this is like your clouds right your clouds have water vapor in them there is water vapor and they're Loosely bonded together but um you don't have stable hydrogen bonding on the other end from liquid as the temperature cools it actually stabilizes these hydrogen bonds much more so that the water molecule does bond with all four other water molecules right each water molecule bonds with all other four molecules and it makes a crystalline structure where essentially it has the space it kind of spaces the water molecules out quite evenly where they have um air pockets in them so as they get cool and they lower to a solid the hydrogen bonds are stabilized and they make a crystalline structure with air pockets in there and that actually makes um ice less dense than water which is weird because when you look at most uh things on Earth um as they cool they get more dense if you remember dense is how many you have per unit area so as they cool they become like most solid things you think of it's more dense the elements are more stabilized um moving less held together in a tighter form there's more of them in um the same amount of space with water it's opposite they are less dense essentially there's less of them in the same amount of space they're kind of spaced out more evenly um which causes ice to float this is why ice floats with most other things if you take them from a liquid to a solid state they would sink but ice floats on the top because it is less dense and this is really important to life because those stable hydrogen bonding as the liquid water cools a solid ice is less dense than at the liquid form causing it to float and it really makes it an insulator to the water um right there's a reason you have liquid water underneath an ice top like a I don't know how many of youve been North but if you go up to like Minnesota in the winter people go ice fishing and sometimes people have done it here but we don't you know ice doesn't last that long uh on our lakes here but in Minnesota they will last for months but there are still things living under that ice because the ice really serves as an insulator to the lake helping keep the temperature um regulated and liquid water so um something that's interesting is liquid water is really most dense and water water itself is most dense around 4 degrees C so it does become denser as it becomes cooler but once it starts dropping below 4° where it's getting closer to freezing remember freezing is 0° C that's where it starts becoming less and less dense and stabilizing these bonds and kind of spreading out almost um so that it is less dense than liquid water when it gets to zero and it floats and um and this is important it regulate it insulates life um in the water in even where its cold regions the next two slides are really related to each other and they kind of relate to the last slide as well it I see these all as um different branches of really overarching property but we kind of say they're separate but they're they're all related and of course they're all related because of water's hydrogen bonding so they all kind of have relation to each other um related to water being less dense as an ice and insulating Lakes it has a high heat capacity um heat capacity is essentially um amount of heat 1 G so just an amount it's just a very small amount of a substant must absorb to raise this temperature 1° C so how much heat does it take to raise something 1° um what this means for water is that it takes time really a longer time to compare to other um elements and compounds and molecules to heat up and cool down um so related to my Lake if you look at a lake temperature um at different depths over a course of a day and then do that like every day over the course of seasons and you're also doing it for air temperature maybe air temperature right above the lake and then like in the same increments above in the air you'll find that air temperature varies far more greatly than water temp temperature um at the surface you do get more variation kind of um you get a bit less variation as you go down but even at the surface compared to air you don't have as much of drastic changes right the air temperature can pretty regularly changes within 20° within a day between day and night and can really even be much greater than that um well I say 20° fhe more than that Celsius um water temperature really doesn't you'll get some change again at the surface but once you're kind of below the surface it's very little change um kind of related this kind of relates to this in the next slide waterfalls right waterfalls are much cooler at the bottom of a waterfall than the top my picture on the right here is of course natural Falls if you've ever been out it's one of our state parks it's beautiful and it's a it's only a little over an hour um East of Tulsa and they have um a short hike it's a little difficult cuz there's a lot of steps so it's not for everybody but a very short uh fairly easy hike um to the waterfalls and you can and there's some paths above and paths below and you will notice just like a drastic change in temperature from when you're on the top to the bottom now you can't get too close to the falls you're not allowed to swim there's a guard rail but um and of course there's other things like you're kind of more exposed where you have some more shade at the bottom but waterfalls absorb a lot of heat right taking that heat and evaporating which I'll talk about evaporative cooling on the next slide um so the temperature even the air temperature is cooler at the bottom of waterfalls and the top of waterfalls all right heat vaporization um so water has a high heat vaporization or something we also call evaporative cooling that water does which is nice a lot of us have used um this is the amount of energy required to change 1 G of liquid to a gas so now we're going from liquid to gas um and water takes a bit right it takes a bit of energy to do that it takes a lot um but that means that water can essentially absorb the heat so again that that kind of this relates to the waterfall as well water is absorbing that heat and evaporating which is taking some of that heat out of the air and this relates to sweating a lot of times we think we're sweating cu the sweat itself cools us but it's not the sweat that cools us and you would probably know this if you've we're actually pretty humid here so youve probably experienced it right on a really humid day and there are some parts of the US that are very humid um but right humid humidity refers to water vapor in the air high humidity means there's a lot of water vapor in the air so when it's a warm day and it's very humid you sweat but what happens that sweat it just stays you you say you feel sticky right everybody feels sticky on a humid day that's because your sweat isn't evaporating because you don't cool specifically from the sweat coming down you you cool when that sweat evaporates it's absorbing the heat from your body the water in your sweat is absorbing the heat from your body which then causes it to heat up and go to a gas State and takes that with you which can help cool your body temperature and this is a way you maintain homeostasis right you're hot and it's also a response to stimuli response to heat you sweat um and the goal right the goal here is though for to maintain homeostasis that characteristic of life to cool your body back down but when it's really humid there's so much water in the air the sweat can't evaporate if the air is already saturated right 100% humidity means the air is saturated with water if you have 100% humidity you can't you your sweat's not going to evaporate because the air is already Satur saturated and that's when you get sticky and you feel really hot because you're you're you're not able to cool yourself because evaporative cooling um is what you use to cool down all right this is going long so I'm going to try to speed through some of these um water is a really good solvent you've probably heard that that's because it dissolves things really well in water so for things like salt sodium chloride we talked about earlier right it's held together by an ionic bond and you have a positive sodium ion and a negative chlorine ion um or should I say chloride ion um and so water the oxygens of water will be attracted to that uh sodium and the hydrogens of water will be attracted to that chlorine and it separates them and this is why when I said um while ionic bonding is really a stronger chemical property in living things it's not as strong because water can break ionic bonds it it depends on the ionic bond and how strong it is not they don't all just like automatically break in water but it can um separate ionic bonds because of um the polarity of water molecules which is why water is a good solvent and so we use it in a lot of stuff right for cleaning um because it does this because it bonds to things and can break them apart dis associate um different compounds and separate them um so the way um I wish want to side note here the way uh salt dissolves is different from the way sugar dissolves and I'll try to talk about that in next uh chapter slides another important property of water is what we call cohesion and adhesion so cohesion is water sticking to itself that's this basic thing because of its hydrogen bonding because of its polarity it has the hydrogen bonds and it sticks to itself that is cohesion that's important that water sticks to itself and then we can have liquid water and do a variety of things um it also causes surface tension so surface tension is um being able toand rupture and so those hydrogen bonds are a bit more stable on the surface of water and um so it kind of can help keep water from breaking and some you know insects have um exploited this by evolving to be able to walk on water they have certain evolved things on their feet and other things about them that um allows them to do this so surface tension and cohesion are important cohesion water sticking to itself that that is a subset of that is causes surface tension which helps water resist breaking the opposite of cohesion is adhesion adhesion is when water sticks to other stuff the way I remember remember the difference between adhesion and cohesion is adhesive tape sticks to other things and when you think of a cohes a cohesive group they're working together as one so cohesion is water sticking to itself adhesion is water sticking to other stuff um this is important because this is how water sticks to other things like your hands sometimes um and capillary action you've probably heard of um capillary action or capillary if you're British um where water sticks to the sides of glass and that's because it's polar and the glass has a charge and so it sticks to the sides of there and can actually be pulled up seemingly Against Gravity well life has taken advantage of this which um really we they figured it out before we figured out capillary action but all the plants of trees actually plants not just trees but the majority of plants that if they have a root they have a root system and um water is taken from their roots to their leaves even in the tallest of trees through these tiny little tubes and water moves up through essentially this capillary action it's moving up through both cohesion and adhesion where it's sticking to the sides of these tubes this they're essentially just dead cells and water sticks to itself and because of um essentially a negative pressure water evaporating at the leaves water can be pulled up without having to use any energy by the plant pull it up from the root all the way to the leaves where they need their water to do photosynthesis hey I'm almost at the end only two more Concepts I'm going to go over one an hour 20 which I hate but um I'll try to keep it under an hour 30 so pH um You probably heard of pH right um this is the potential of hydrogen it's essentially how many hydrogen ions sort of relative to O ions are in water so water H2O will actually disassociate so we have this right goes back and forth between hydrogen ions and O negative ions remember water is H2O and it's that oxygen bonded to two hydrogens well sometimes they separate and you get like that goes off and you get a hydrogen ion and an O negative ion this would be an O negative because the hydrogen ion will take will not have the electron it will just be a proton by the way that's something you should know that hydrogen ions are the same thing as protons um that's going to be important concept next unit in understanding something um and so this o here would have that electron and so it's O negative and so it ionizes and water into these two different ions and it goes back and forth so in pure water if you just have pure water with nothing else in there it will do this and it's still what we call pH of 7 it's a constant pH 7 is what we call neutral pH is on a scale of 0 to 14 and seven is neutral and even though there will be H+ and O negatives as long as they're equal to each other it's still neutral it's when there starts differentiating if there becomes more H+ ions a solution becomes more acidic essentially more relative to O Negative so there's kind of two ways it could either increase in O+ ions or decrease in O negative ions both of those will make more H+ ions relative to O makes it more acidic and the pH decreases on the other hand if there are more oh negative ions when um oh Nega increases or H+ decreases and so you have more O Negative compared to H+ pH increases and the solution becomes more basic so this happens when there's there's other stuff in water we'll look at this on the next slide so here's a general scale um true pure water which called distilled water um is at a ph of 7 um if pH decreases anything below seven even 6.9 um it becomes acidic anything above 7.1 is basic just exact seven is neutral and the further you get away the more O negative ions you have slash the less H+ ions you have typically it's really less H+ ions the more acidic you get the more H+ ions you have the less O negative ions you have until at zero you'd be saturated of H+ ions um there are properties like you know some things you're like oh well that's a really high pH but like you could still eat or drink it and some things can have a really low PH you still eat or drink while other things are very costic and dangerous so there is other stuff what is in these Solutions depending on how dangerous you know um we kind of say basic really high basic or alkaline things tend to be CTIC and um acidic stuff tends to burn right you probably you know like lemon that lemon like especially if you have a cut that really Burns um uh your body regulates its pH blood is actually slightly basic but it it really regulates it into a into a specific region the other thing I want you to note is that this is a logarithmic sale so there is a 10 times difference in every level so if you're going from 7 to six that is 10 times more hydrogen ions at six than there were at seven and then if you go from six to five that's another 10 times it's a 10 folds that means you times them so if you go from 7 to 5 you have a 100 times 10 * 10 you have a 100 times more hydrogen ions if you go from 7 to 5 and if you go from 5 to three that's a 100 times more hydrons and if I go from 7 to four that's a thousand times more hydrogen ions on the other end if I go from 7 to 8 that's a 100 times less I'm sorry 10 times less excuse me 10 times less hydrogen ions I'm sorry if you hear that they're working and it's very loud in the background if you go from 7 to 9 that's 100 times less hydrogen ions so it's a tenfold in every increment my gosh I hope you guys are not picking up the background noise um buffers help maintain internal solution so there's all types of buffers we have buffers we use when we make when we do chemical reactions in a lab um they're helping to keep the pH in a specific range they typically contain um typically a weak but sometimes strong acid and or base but it's kind of a combination where it will help control bring if something's too acidic it helps make it a bit more basic if something's too basic or alkaline it brings it a bit more acidic you know it's bringing it back to where it needs to be um with our blood we think neutral because we're close to neutral but it's not always sometimes things are always acidic but they can still get too acidic right something might want to be maintained at a pH of four which is quite acidic but when it's getting to three a buffer is used to help bring it back up to four so a buffer doesn't necessarily have to keep something neutral or in a neutral range it's just helping to keep it in a specific PH range um I'm talking about this here this will be important for you going into your health sciences and Health Care studies um you'll use buffers and IVs um and in other times um right you've probably heard of alkalinity and um acidosis in these you know blood can get out of whack and become get too low and get too high um the body typically wants its blood between 7.2 and 7.6 it can go lower and can go a bit higher um but it's it's typically trying to maintain it in that range so when it starts getting below that or above it it's trying to bring it back to that range um and um bicarbonate sodium bicarbonate well it's bicarbonate here and carbonic acid are how it's regulating right water and CO2 are common in your blood you have a lot of water and you're getting that CO2 from your cell reactions and so your blood is like consistently depending on like what breath you're taking whether you have and right your veins or arteries how much oxygen versus how much carbon dioxide is there is affecting its pH and so it's in this kind of constant change going a little bit up a little bit to acidic and then you know adds a buffer and might bring it a bit more basic and then so um bicarbonate is used um by us to help maintain that blood pH last part this is important to chapter 3 it's a precursor um originally I had moved it to there but um your book includes it in Chapter 2 so I decided just to keep it um so carbon's really important I want to note we organic is in chemistry and biology and science do does not mean the way you think of it with your food how your food is made organic means carbon based carbon um attached to hydrogen specifically so like CO2 is not organic because it's a carbon dioxide it has attached to oxygen but methane CH4 is organic because it's carbon attached to hydrogen um and that carbon based life is what we considered organic is really important on Earth and so why is carbon so important well if you look at Carbon and its veence electrons it has four veence electrons 1 2 3 4 remember how I said earlier like here lithium likes to lose one and becomes positive Boron 2 has three it'll lose those three and become positive so these tend to become over here on the left become positive ions over here nitrogen oxygen Florine they're all like florine's missing one electron Oxygen's missing two one 2 nitrogen is missing three so they can easily pick up electrons although they do like to make bonds as well they like to share them particularly oy nitrogen um and pick them up Florine might become a um a negative ion carbon has four it's kind of right in the middle right eight fills it up and it's got four so it doesn't like to lose or gain electrons it likes to share so it bonds really well it makes Cove valent bonds and calent bonds are very strong and water so carbon is the basis of what we call our macro molecules these four classes of molecules that are used and needed by living things and carbon is found in all of them and is really the the backbone to that um so carbon we have carbon based life here on Earth because of its ability to bond and um I'll just take a a couple minutes here to look at a few things about carbon and functional groups I skipped the last slide because it's pretty much everything I've already said so I wanted to note here carbon can make Chains It's not shown here I think your book talks about it but it can make chains which are important it can make rings these ring structures um sometimes nitrogen and actually sometimes oxygen can be put in in these ring structures um so it's really versatile in biology structures function so these different structures that makes allows it to essentially do different functions um and these are all organic you'll notice it's carbon attached to hydrogen so these are um we it's here the hydrocarbon Rings um it's organic but when we start adding um oxygen in here as well and sometimes nitrogen carbon can start doing some really cool stuff and that is um what we use in need in living things which that will be our macro molecules on next time I just wanted to kind of set up what carbon's important here it can make these different structures which allow it to have slightly different functions molecules can also come in isomers your books goes into more details about isomer I don't need you to know the different types of isomers I'm not going to ask you about it that's definitely more chemistry focused and really we don't need to know but something I I do want to point out isomers are when it has the same molecular uh chemical formula but it's really a different structure it looks different so they have like these have the same number of carbons and hydrogens so they have the same chemical formula but their structure is different the way the bonds are forms or how it looks and there's different types where some can just be like miror images of each other um some just have a different type of arrangement so there's different types of isomers but all you need to know about isomers is its molecules they're molecules and they're typically we got carbon based um that have the same chemical formula but different Arrangement don't get this confused with isotopes Isotopes are the same element with different number of neutrons there we're just talking about an element it's isomer we're talking about molecules so these are larger that uh interact more or like cause different things in particularly living things if we're talking about biology all of that that talked about the carbon led to functional groups this is why I want to go over it and I'll probably maybe touch on at the beginning of chapter 3 as well so functional groups are these essentially chemical groups with a specific elements in a specific bonding orientation that give properties to what they're attached to so you've probably heard of things that end in all like right alcohol alcohol means there's a a o group on it oh is a is an alcohol group and so [Music] um alcohol um has an o group on it and so things are named by what is it um attached to it like an amine group down here let's look at Amino has um a nitrogen and two hydrogen sometimes it actually can have three hydrogens um is the Aman group so we'll learn about amino acids they have an Aman group on them the r refers to what they're attached to it could be a longer molecule it's usually a a carbon but that changes the r is variable meaning like what it's attached to is changing these are the functional groups that they're attached to some molecule um but it gives them a property so like our hydroxy group here is that o I was talking about right it makes it polar because there's that negative charge and so it gives it a polarity to it um carbonal groups is the carbon double bonded to an oxygen also polar a methyl group that's the ch3 if it's bonded to a molecule if that part of it is non-polar so some molecules can have non-polar and polar Parts which even gets more confusing um so we have these different functional groups and they give properties to the um molecule they're attached to phosphate groups are important you'll see this in our macro molecules and phospholipids they have phosphate groups so the the kind of important ones I I want you to take a look at Amino and phosphate those are going to be important and then um Carbono and carox will kind of come up a bit too so knowing those um but they're important to giving properties to the molecules that they're attached to in a fun video I show in class if I have time up to you if you want to watch it have a good one sorry that took so long