As we transition now to
carbon dioxide transport,
we’re going to use a compare and contrast
point of view to get us started.
Since we’ve already covered the
O2, I know you know this now,
and what we’re going to
do is add the CO2 to that
so that you can start
to understand CO2
and then we’ll finish up
with the gas transport.
So the first aspect is that
CO2 more in the arterial side
of the circulation is dissolved
than what is for O2.
Now, the partial pressure of CO2 on the
arterial side of the circulation is lower.
So this must mean that carbon dioxide
solubility is greater than oxygen solubility.
Also, less of carbon dioxide
is bound to hemoglobin.
So there must be a different way in which
it’s bound to hemoglobin molecule itself,
where it has a low
amount of affinity,
compared to oxygen, which
is 98% bound to hemoglobin.
The final thing that’s different
with carbon dioxide transport
is most of it, 90%, is in
the form of bicarbonate.
So bicarbonate is part of a
reaction in which you can take CO2,
add it to water, it can form carbonic acid
and then dissociate into a
bicarb ion and a hydrogen ion.
And this is this bicarb that
is in the form of carried CO2.
So you always think of CO2 as a gas, but
in this case, CO2 can be in ion as well.
And that’s how your body transports
the majority of the carbon dioxide
within the blood, is in the form
of an ion, not in the form of gas.
Let’s go through each of
these mechanisms one by one.