hi every Dr Mike here in this video we're going to make sense of acids bases and buffers finally now let's take a [Music] look so to begin we need to understand a couple of things first thing is this your body is filled with ions these are charged atoms or elements examples of ions include sodium and pottassium and calcium and also hydrogen but there's others there's bicarbonate there's chloride there's magnesium regardless they're charged atoms or elements they all play roles in the body for example sodium and potassium really important for nerve conduction calcium muscle contraction and hydrogen ions what's that important for H well this is the question for the day right because if I were to measure your sodium concentration in your blood it's going to be about 140 Mill but if I were to measure the concentration of hydrogen in your blood it's going to be 0.00004 Millar there's a huge difference hydrogen concentration really low and this is important because we need to maintain a low concentration of hydrons because it's super reactive and you might think but it's charged just like all the others why is it so reactive think about the periodic table right right hydrogen helium lithium burum boron carbon hydrogen's the first one it's really tiny it's simp it's basically if you look at it in its ionized form it is just a proton and then as you move through you have bigger and bigger uh uh elements like you get to sodium right which is going to be big with its little charge and then you have pottassium which is even bigger as an atom with its little charge so hydrogen right which is just a charge compared to the others its size to charge ratio right huge charge compared to its size so it's super reactive which means it goes around the body trying to steal electrons from things like proteins and it can damage the proteins and a whole body is made out of proteins they form the structural components of our body but also the functional like enzymes you don't want to damage the proteins so we need to maintain these low hydrogen ion concentrations and as you know from my previous videos we measure hydron concentration not like this but as pH so how do we maintain our hydron concentration as being low well the first thing is we need to talk about how we even make hydrogen ions where do these hydrogen ions come from great question Dr Mike so we need to talk about acids acids are what produce hydrogen ions if I were to draw up the most basic or I should say not basic I need to be careful cuz we're talking about acids and bases the most simple way to write an acid I could write ha so let's say that is an acid that's an acid what acids do by definition is they donate hydrogen ions right so this acid will donate a hydrogen ion now as you know a hydrogen ion can also just be called a proton they're synonymous so keep that in mind if I were to donate that hydrogen ion what am I left with I'm left with the A and it's going to be negative cuz that's neutral so the positive and negative charges balance out if I steal the positive there's the negative what we call this is the conjugate base now this is where we can introduce bases I said the definition of an acid is it donates hydrogen ions the definition of a base is that it absorbs or mops up hydrogen ions which means this equation can effectively or theoretically go in the opposite direction where the base mops up the hydrogen and produces the acid again very important concept what determines how an whether an acid goes in that direction or whether the base mops it up and goes in this direction well to understand that we need to draw up some actual physiological or biological acids that we have in the body there's a whole bunch I'm going to drop some some important ones so we have hydrochloric acid hydrochloric acid we have H2 P4 Nega which we call dihydrogen phosphate or phosphoric acid we can have h23 which we call carbonic acid we can have like you've probably heard of amino acids and fatty acids and lactic acid and pyruvic acid so there's a whole bunch let's talk about amino acids just very quickly amino acids so amino acids are really really interesting remember an acid can donate a proton so if I want to draw up an amino acid again a simple version carbon hydrogen there's this functional side group that has that can change that's what determines the flavor or the type of amino acid that we have but we also have a a carboxy end right this is what we call the C Terminus that's the caroal end and we have an aan Terminus which we call the N terminal right so we got the N terminal aan end C terminal carboxy and have a look at it right this is really interesting this C Terminus can donate the hydrogen onon into the solution and if it does what does it produce Co Nega so it's a it's an amino acid because it can donate a proton beautiful it can also go in the opposite direction right and be reprotonated bring that prot proton back wonderful this side can do the same thing this side can take on hydrogen ions and if it does it becomes NH3 positive or it can release a hydron from mh3 positive and bring it back to nh2 so you've actually got two ionizable groups on amino acid sort of acting as and I haven't defined this yet but as like a double buffer so let's write this down here let's write the way I'm going to write this down is like this you've got an amino acid with the C terminal or you've got an amino acid with its protonated amine terminal all acids so since they're all acids what do they do they all disassociate to release hydrogen ions so that's easy so we know that because they're acids but what do they produce they conjugate base so what's the conjugate base I remove hydrogen ion I'm left with chloride ion I remove a hydrogen from here I've only left with one hydrogen one phosphate and four oxygen but two negative so hydrogen phosphate here I'm left with a hydrogen a carbon and three oxygen and negative that's called bicarbonate this the carboxy end I'm left with Co negative and here I'm left with the aan end is nh2 these are the conjugate bases from the acid all right here's the thing I asked the question you can theoretically say that because a base can bind to a hydrogen ion to produce an acid but an acid can disassociate into hydrons and the conjugate base what determines which direction it goes all right that's determined by two important things the ph and the pka the ph and the pka related terms the pH is the concentration of hydrogen ions in the immediate solution that it's in right we know in the body it should be at 7.4 that's the pH the pka is the value that each acid has that tells you how likely it is to donate its hydrogen ion its proton in a particular pH you might go oh what does this even mean all right let's think about it like this right let's let's say let's just write up the the basic sorry the simple form of an acid ha reversibly gives us hydrogen ions plus the conjugate base and let's write it on a seesaw or in the US what do you call it a TA tot now we know that the pH of the solution should be 7.4 right now if the pka the pka which is the value that's given to the acid to tell you how likely it is to donate its hydrogen ion if that's the same as the pH it simply tells you that if that's the same as that it's balanced it's going to go equal in that direction as it is in that direction so it's as likely to donate protons as it is to bind them up that's actually what we call a buffer a buffer is when the pka is as close as it possibly can be to a pH to the pH of the solution and it can release protons when needed and bind them up when needed so that is a good buffer excuse me a good buffer is when the pka and the pH are close together when the ph and the PK they'll never be exactly the same at least not biologically but when they're as close as possible to each other that makes a really good buffer cuz what a buffer does is it resists drastic changes in PH I said to you we've got low numbers of hydrogen ions we want to keep it low so if for whatever reason the hydrogen levels accumulate in our blood what do we do all good we mop it up so it's not available what if the hydr levels go too low I know that's also a problem let's release some buffers are perfect CU they can go in each Direction now if an acid has a PKA that's less than the pH so let's say the pka is 6.1 that's obviously less we've now just moved it from being centered in the middle and nice and balanced to on this side which means this whole thing goes like that now if it goes like that what goes up the hydrogen ions go up so if the pka is lower than the pH you produce more hydrogen ions you produce more hydrogen ions right it's more likely to go in that direction if the pka is higher than the pH you probably know what's going to happen in this case let's say 8.1 it's weighted in this direction that side goes up so you form more acid you mop up more hydron so that goes down right makes sense perfect so what determines How likely it is to disassociate or not has to do with both the pH of the environment that it's in because that can change too right that can change as well so for example if you've got an acid that has a pka of 6.8 and we know the pH of the body is 7.4 but let's just say the pH changed and the pH went down to 7.25 right not a good number but let's say simp it's closer to the PK it's now becoming a better buffer it's now this assd has now become a better buffer because it's closer the ph and the p k are closer I'll give you an example of that in a sec all right I promise I'll give you an examp a good biological example of that in a second all right so here's the thing hydrochloric acid its PKA is like negative six or something it's all the way down here which means it goes well up which means this acid hydrochloric acid it basically will only go in One Direction it will only disassociate to produce hydrogen ions and chloride so it's not a you can't use it as a buffer it won't go in the opposite direction hydrochloric acid is what we call a strong acid hydrochloric acid is what we call a strong acid strong acids basically are more likely to fully disassociate into its hydrogen and and the conjugate base right but you can have what's called a weak acid all of these are weak acids weak acids let's write this down all of these are called weak acids weak acids have the pka and the pH closer to each other so they can go in both directions and they're more likely to so which means all of these can act as buffers and this leads us to our next Point buffers so the body has three important chemical buffers they all by definition buffers have to be weak acids so the three chemical buffers we've actually drawn up here the three chemical buffers are the phosphate buffer the bicarbonate buffer and the protein buffer also know as the amino acid buffer these are the three most important chemical buffers of the body let's go through them so let's start with phosphate right the pka of dihydrogen phosphate I think it's around about 6.8 it's relatively close to the pH it's actually the of all three it's the closest PKA to the pH in the body which means theoretically it's the best buffer but the problem with phosphate is that it's mostly if that's a cell you got the extracellular fluid and the intracellular fluid phosphate is mostly in the intracellular fluid H2 P4 Nega not much in the extracellular fluid so phosphate is a good intracellular fluid buffer but not great as an extracellular fluid buffer the other thing is this right now the kidneys you filter blood right so if I were to draw up a kidney let's draw up a kidney here you know that you've got with the kidney the cortex that's the outside here and the medala in the cortex you've got all these strange looking what look like Pac-Man heads with worm bodies which we call nephrons that's a nefron there's 1 million per kidney they filter the blood so the renal artery that comes in will enter and will Branch multitude of times and finally you've got these terminal branches that we call afren arterials that enter this nefron and that's what filters the blood in a million of them right so let's make this bigger and just have a quick look if here's a nefron it's like a Pac-Man head and then it's got this snake body right and you've got the blood vessel entering turns into a capillary bed called the glus and then it leaves so blood enters blood leaves this is where stuff gets filtered there's a mem a number of membranes here that can filter things this is what we call the renal tubu and the renal tubu has renal tubular cells now importantly the renal tubule and the tubular cells increase the concentration of phosphate right they increase the concentration of phosphate so the renal tubules they also the pH changes you're starting to make urine here right so the pH drops and as the pH drops in this case it's getting closer to the pka of phosphate making it a better buffer so effectively in the renal tubules and the tubular cells phosphate becomes a really important buffer all right so there we go for phosphate let's skip bicarbonate for a second let's talk about proteins proteins are really important buffers because proteins are everywhere so really abundant inside cell so a really important intracellular fluid buffer and most of the body's buffering like 60 to 70% of the body's buffering happens inside of the cells and most of that is because of proteins so it's the most abundant it's the most abundant buffer but it's not the most important strangely enough how does it work as a buffer we highlighted this earlier but let me just reiterate some points right you've got an amino acid with its functional side group it's got its carboxy end and it's got its amine end if the solution becomes too acidic so too many hydrons accumulate in the cell for example or in the body we want to it out right we want to mop them up so the hydrogen can bind to the aan end and what do we end up producing NH H3 positive brilliant this amino acid just buffered out the excess hydrogen ions by binding them to the amine chain the amine group what if we don't have enough hydrogen ions in the blood easy the carboxy end will donate hydrogen ions and what do we end up getting Co negative so now Vice Versa that can happen in the opposite direction they can bind back and that can be released back so effectively proteins or with their amino acids are really good buffers because they've got two ionizable side groups here that can donate and release protons depending on the pH of the solution and its own PKA and here's the other thing the side chain here can be basic or acidic meaning there's amino acids that in addition to having the C Terminus have another carboxy and here as its functional group which means it can act to donate or release protons or you can have amino acids that have an amine group as its functional group and can do the same thing so obviously what I'm saying is amino acids can be really great buffers but they're not the most important the most important are the bicarbonate buffers right so now we need to talk about the bicarbonate buffer system here's the thing about the bicarbonate buffer system we've drawn it out sorry we've drawn it out here but it's a bit more than this think about your body you take in oxygen you take in nutrients like glucose and you make energy ATP what's the byproduct of that metabolism it's carbon dioxide so all the cells of your body produce what do they produce they produce carbon dioxide now this carbon dioxide needs to get to our lungs to be breathed out it's the exhaust fumes of the body but to do that it needs to jump into the blood to get transported to the lungs you know that most of the blood is water so that carbon oxide needs to bind to water in our blood what does it produce what does it produce well it produces two hydrogen one carbon and 1 2 3 oxygen wait a minute that is carbonic acid which also means that it's going to split apart cuz like I said acids hate themselves they split apart to produce hydrogen ions and let's get rid of that bicarbonate ions and it's reversible cuz it is a buffer all right why is it such an important buffer I'll tell you why because unlike these other buffers which we call nonvolatile buffers this buffer the bicarbonate is a volatile buffer what that means is part of the equation produces a gas that can be breathed out that's why it's called volatiles you can actually play with around with the concentration of hydrons through breathing right have a look at this right have a look I love this if you increase the amount of carbon dioxide in your blood it will bind to the water produce carbonic acid which will split itself apart to produce hydrogen ions and your blood becomes more acidic because of the concentration of hydron go up so effectively increase carbon dioxide in the blood increase the amount of acid or hydron in the blood but because it's reversible hydrogen ions combind to B carbonate and produce more carbon dioxide that we can breathe out so the way You' think about it is in both directions right like this Something's Happened in my body to produce too many hydrogen ions don't worry by carbonate will bind with it produce carbonic acid which will split apart and produce carbon dioxide and we breathe it out when you breathe that carbon dioxide you breathe out acid effectively cuz think about it if I don't have if if I hyperventilate I breathe away all my carbon dioxide it goes down less carbon dioxide to bind with water less carbonic acid less hydrogen ions now again you might be thinking why is it the most important buffer because of this this end of the equation is dealt with by the lungs and because right now I can either hold my breath what am I doing when I do this my carbon dioxide levels go go up if they go up it produces more hydrons or I can hyperventilate and get rid of it I can change the pH of my blood in the short term through breathing and so lungs can change the pH in the short term brilliant on this side of the equation the kidneys can play around with your bicarbonate and you can either make more bicarbonate reabsorb more bicarbonate or pee out more bicarbonate right and that can change your blood pH but that takes longer hours to days so this is a longer term control so have a look we can control the pH of our blood through our lungs and our kidneys in the short term and long term which makes it an extremely important buffer because it can fine-tune the pH of our blood so the three buffers of the body phosphate bicarbonate and proteins most important bicarbonate in a future video we're going to focus on this buffer in isolation and talk about all the different types of acidosis and alkalosis I'm Dr Mike hi everyone Dr Mike here if you enjoyed this video please hit like And subscribe we've got hundreds of others just like this if you want to contact us please do so on social media we are on Instagram Twitter and Tik Tok Dr Mike todorovich d m i k t o d o r oov i c speak to you soon