This video explains the fundamental concepts of acids, bases, and buffers, emphasizing their crucial role in maintaining the body's pH balance. It details how hydrogen ions are produced, the definitions of acids and bases, and the mechanisms by which buffers, particularly the bicarbonate system, regulate hydrogen ion concentration.
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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]
[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
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
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
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
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
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
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
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
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
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
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
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
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
things
this is what we call the renal tubu and
the renal tubu has renal tubular cells now
now
importantly the renal tubule and the
tubular cells increase the concentration
of phosphate right they increase the
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
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
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
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
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
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
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
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
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
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
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todorovich d m i k t o d o r oov i c
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