00:01
So now let's switch
and talk about
what happens with carbon
dioxide transport.
00:08
So when carbon
dioxide transport,
it is transported in
three different ways.
00:13
First it can be
dissolved in plasma.
00:17
Also, like oxygen,
carbon dioxide can also bind
to the hemoglobin molecule.
00:24
Instead of binding to the
heme, however,
the carbon dioxide
binds to the globin part
when carbon dioxide is
bound to hemoglobin.
00:34
It is referred to as
carb amino hemoglobin.
00:39
The remainder of our carbon
dioxide molecules, however,
are transported by way
of bicarbonate
ions in our plasma.
00:49
These bicarbonate
ions are formed
by carbon dioxide
combining with water
to form a molecule
known as carbonic acid.
00:59
This carbonic acid can
then be dissociated
into bicarbonate and H+.
01:08
So we see this
chemical formula here.
01:11
Remember carbon
dioxide plus water
gives you carbonic acid
the carbonic acid can
then dissociate into
hydrogen and bicarbonate ions.
01:22
So this is a reversible process
that can occur either
in the blood plasma,
but can also occur in
our red blood cells.
01:32
The red blood cells is
where this occurs more
often and the reason why
is because our red blood cells
have an enzyme known as
carbonic anhydrase.
01:44
So in our systemic capillaries,
the bicarbonate can be
created and then diffuse
from these red blood
cells into the plasma.
01:55
The out rush of bicarbonate ions
is going to be balanced
by an influx
or a moving in of chloride ions
so that we maintain
the negative charged
in the cells.
02:09
This movement of chloride
as the bicarbonate moves out
and the chloride moves
in is referred to
as our chloride shift.
02:21
So now let's look
at this in an image.
02:23
So recall there are
three different ways
that we're going to
transport our carbon dioxide.
02:29
We can transport
carbon dioxide directly
by dissolving it in our plasma.
02:34
We can also transport
carbon dioxide
by binding it to water
to form carbonic acid
and then dissociating it
into bicarbonate and H+
thus transporting
the carbon dioxide
by way of bicarbonate ions,
and then the third way
is by the carbon dioxide
binding to hemoglobin
in order to form
carbamino-hemoglobin.
03:02
So this process is
going to be reversed
and our pulmonary capillaries
compared to what
happens in our tissues.
03:10
So whereas in the tissues
the bicarbonate ions
were moving out of
the red blood cells
and this case the
bicarbonate ions
are going to move into
the red blood cells.
03:22
Subsequently,
the chloride ions
are going to shift
in the opposite direction
and move out back
into the plasma.
03:31
The bicarbonate ions
are now going to bind to H+
in order to form carbonic acid.
03:40
The carbonic acid is
then going to be split
by a carbonic anhydrase
into carbon dioxide and water.
03:49
And now the carbon dioxide
is going to diffuse
into the alveoli and
eventually be exhaled.
03:57
So if you recall the
chemical reaction,
this is the reverse of
the chemical reaction
where now we are starting
with bicarbonate in H+
going through Carbonic anhydrase
and moving back into,
carbon dioxide and water.
04:18
So we can see this
depicted here.
04:21
So again, the carbon
dioxide can either diffuse
directly out of the plasma
which happens less often
or we can do the reverse of
the reaction we
saw in the tissues
and our bicarbonate is
going to be converted
into carbon dioxide and water
or we can also get
unloading of carbon dioxide
from the carbamino-hemoglobin.
04:47
So the amount of carbon dioxide
that is transported
is going to be affected
by the partial
pressure of oxygen.
04:56
The lower the partial
pressure of oxygen
and the hemoglobin
saturation of oxygen
the more that carbon
dioxide can be carried
on these hemoglobin molecules.
05:08
When we reduce hemoglobin,
this is going to
buffer the H+ ions
and we are able to now form
the carbamino-hemoglobin
more easily.
05:19
So reduced hemoglobin
that does not contain
oxygen molecules
are able to better
bind to carbon dioxide
in order to form
carbamino-hemoglobins.
05:34
So this process is
going to encourage
the carbon dioxide exchange
at both the tissues
and at the lungs.
05:42
So at the tissues,
as more carbon dioxide
enters the blood
there's going to be more oxygen
that's going to dissociate
from hemoglobin.
05:51
We already talked about
this as the Bohr effect.
05:55
However as the
hemoglobin releases,
the oxygen and becomes reduced
it is now more readily
able to bind to
the carbon dioxide to
form carbamino-hemoglobin.
06:09
This is what we refer
to as to Haldane effect.
06:13
So carbon dioxide actually
plays an important role
in our Bloods pH levels.
06:21
So if the H+ concentration
and our blood rises,
or the blood
becomes more acidic,
we are going to remove this H+
by combining it with bicarbonate
to form carbonic acid
and then eventually forming
carbon dioxide and water.
06:40
However, if the H+
concentrations begin to drop
then we're going to
actually start to dissociate
our carbonic acid into
H+ and bicarbonate.
06:54
The interesting thing about this
is that if you go back to
that chemical reaction,
this is referred to as
Le chatelier's principle
where the increase on one side
of an equilibrium reaction
drives the reaction and
the opposite direction
and vice versa.
07:13
So because of this
our bicarbonate is going to be
considered our alkaline reserves
and what we refer to
as the carbonic acid
bicarbonate buffer system.
07:25
So when rh+ gets too high
we are able to buffer it
with bicarbonate ions.
07:33
Changes in our
respiratory rate in depth,
are going to be able to
affect our blood pH as well.
07:40
So when we do slow
shallow breathing
this causes an increase
in the concentration
or partial pressure
of carbon dioxide in our blood.
07:51
This is going to shift
that carbonic acid reaction
toward the production
of H+ and bicarbonate
and therefore is going to
result in a drop in our pH.
08:06
Opposite to this,
if we undergo rapid
deep breathing
we're going to be releasing
more carbon dioxide
than our body should
and this can result
in a rise in our pH.
08:20
Changes in ventilation
can help adjust the pH
when the disturbances are
caused by metabolic factors.
08:27
So for example,
if you have something
going on in your body
that is causing your
blood pH to go up or down
our body can adjust to this
by changing our
breathing in order
to adjust the ph
and this is a very
quick reaction.