The question about homeostasis in acids and
bases clearly we want to maintain a steady pH
in any biological system. So here is an equation
about the bicarbonate buffering system.
And this is how we are able to maintain a
constant pH in the blood while transporting
carbon dioxide out in the blood. Because carbon
dioxide will generally create a more acidic situation.
So again acids are any substances that increase
hydrogen ion concentration. In this case,
if we look at carbonic acid it dissociates
into bicarbonate and hydrogen ions.
And those hydrogen ions in solution will lend
themself to increasing the acidity or
decreasing pH. Remember acidity is a measure of
hydrogen ion concentration. And the lower
the hydrogen ion, I mean the lower the pH, the
more hydrogen ions there are in that solution.
And bases increase the hydroxide ion
concentration. So in this case bicarbonate
is a base. It's going to pick up hydrogens,
pulling them out of solution and thus effectively
increasing the hydroxide ion concentration. In
this buffering system, we see that hydrogen ions
can be picked up or dropped off. And that
picking up or dropping off of hydrogen ions
lends itself to maintaining a constant pH. So
a buffer is anything that resists pH change
because it picks up or releases hydrogen ions.
So here I think that you can see that chemistry
is integral to the study of biology.
It's the behavior of electrons around the atoms
of the SPONCH elements that will allow
bonding of molecules. We've learned about ionic
bonds, covalent bonds and hydrogen bonds.
Again, covalent bonds are the very strongest.
Single, double or triple covalent bonds.
Ionic bonds are the next strongest. And the
weakest of the bond types are those hydrogen bonds.
So everything that happens in Biology is because
of these chemical reactions. Most commonly we'll see
covalent bonding in molecules. For example here
in the process of photosynthesis where we
capture energy from the sunlight and put it
together with carbon dioxide and water.
We're exciting electrons. Taking them up to
higher electron shell levels and adding energy
to a molecule. We end up producing glucose. That
glucose is then something that we might consume
and break down and gain the energy from it. So
then in that case we're lowering electrons
in their energy levels to lower shells. And
releasing energy that we capture in the form
of ATP which is the fuel that all of our bodies
rely on to operate. So hopefully you've gained
some insight into how important chemistry is to
understanding biology. And you're in a position
where you could explain the difference between
covalent, ionic and hydrogen bonds
as well as determine the relative strengths of
each of those bond types. In a scale of
covalent, ionic and hydrogen being the weakest
of those bonds. And finally you have a
brief understanding of acids, bases and the
importance of buffers in biological systems.
In the next lecture, we're going to start putting
together all of these smaller molecules in order
to build macromolecules such as proteins,
carbohydrates, fats and nucleic acids.
So that we can finally build a cell.
Thank you so much for your attention
and I look forward to seing you in the next lecture.