Acid-Base Chemistry, pH, and the Human Body


We have seen
from the previous video that the pH scale
is an effective measure of how much acid we have
in a solution. The acidity is based
on a few factors, such as the concentration
of hydrogen ions, hydronium ions,
and/or hydroxyl ions. Our bodies need to maintain
a very narrow range of these ions, and in effect sustain equilibrium between the concentrations
of these ions. We call this maintenance
homeostasis. Dealing with acids and bases is one of the highest priorities
for the body, since we can only survive in a very narrow range of pH. When we try to describe this range, we refer to the pH scale and its importance in homeostasis
in our bodies. This short video will try to
apply the definitions of acids, bases, and pH, to a scenario of when blood chemistry
is altered in our body. It also will hopefully
connect these concepts to the Bohr and Haldane effects that are explained in
the next video in this series. Given the fact that blood plasma is 92% water
and other blood components, it ends up roughly consisting of
55% water after we calculate things in like the proteins,
the cells and glucose, etcetera; that is other blood components. Given this fact and that our
blood pH is roughly 7.4, it is interesting we start having
issues in our body at 7.5. This is very similar
to the last video’s example of acidification of the oceans, in which a very small change in pH will have a large impact
on living organisms. When carbon dioxide from our cells
interacts with the blood plasma, which is mostly water, it forms carbonic acid. This carbonic acid can also dissociate into
bicarbonate and hydrogen ions. By definition,
carbonic acid is an acid and when it dissociates
into the hydrogen ions you see the right part
of the equation. If you add more carbon dioxide
to the system, you increase the amount
of carbon dioxide, and actually push the reaction
to the right. This is what happens in the presence of the
enzyme carbonic anhydrase. The reverse can be the case
in that you can lower the amount of carbon dioxide, and you can get a situation
that is the reverse. If we reduce the amount
of carbon dioxide, we get a pull to replace
that carbon dioxide and the reaction facilitated through
carbonic anhydrase. And what this ends up doing is lowering the amount of
hydrogen ions in solution. If you lower the hydrogen
ion concentration, you are in effect taking out the acidity- you are taking out the amount
of carbonic acid because it is all flowing to the left. If you are removing
carbon dioxide from the system, you are lowering the amount
of carbonic acid, and therefore, lowering the amount
of hydrogen ions. And in effect, what you’re doing
is raising the blood pH. So that’s what’s happening
when we start hyperventilating- we are raising the amount of
bases in your blood because you are taking out
the carbonic acid and the hydrogen ions. And this is one of the reasons
why you are told to breathe into your hands
or actually breathe into a paper bag to recover the carbon acid lost. By recovering the carbonic carbon dioxide, you are reestablishing
a normal blood pH. Every day of your life, every second of your life, you are dealing with acids and bases
and the chemistry in your blood. The next video will detail
the Bohr and Haldane effects in your body and hopefully further your understanding of why chemistry is so important
to your daily lives.

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