Ph Homeostasis – How Atoms Come Together to Form a Molecule

00:00 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.

00:15 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.

00:29 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.

00:44 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.

01:06 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.

01:48 So here I think that you can see that chemistry is integral to the study of biology.

01:55 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.

02:11 Again, covalent bonds are the very strongest. Single, double or triple covalent bonds.

02:18 Ionic bonds are the next strongest. And the weakest of the bond types are those hydrogen bonds.

02:25 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.

02:44 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.

03:49 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.

04:01 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.