BI222, Video 1

I'm going to show you guys a couple of really complicated things, so don't run away, all right? When we're done, you're going to say that was nothing. Complicated thing number one, this thing called glucose. Now I want you to look at this, and I want you to understand something. Every point on here, okay, represents an atom of carbon, and there's a C right there, okay. So that's a molecule of glucose, and remember the points, carbon. Right?

Let's look at this one. Whoa, man! Don't run away! This isn’t scary. This is a molecule of DNA, but once again, what are you seeing a lot of here? A lot of points, a lot of points, and some Cs drawn in there. Getting any ideas yet? Here comes a typical fat. Seeing anything in there that reminds you of glucose and say DNA? You see the theme? Carbon is kind of important, and all three of these things I just showed you, and I could give you molecule after molecule after molecule—and I talked to you guys about SPONCH, and you know that the "ch," the C there is about carbon—carbon is literally what our life is based on on this planet. We are called carbon-based life forms; you and worms and plants and bacteria, everything, carbon-based life forms, okay. When we go out and look at other planets and sample the soil, we're looking for carbon-based life forms, because it looks to us like carbon is a truly important thing to life.

Let's see why, and it has to do with the structure of the atom of carbon. Now you may know that the electrons on the outer shell of any atom—of any atom, not animal—of any atom are the things that cause it to bond, and carbon has four electrons on its outer shell. Now if you remember something about bonding, you remember that carbon's atoms are spaced like this in a foursome around there, and that it wants with that octet rule, it would like to have eight there. But the problem is—and not like to, like it doesn't talk to me or anything, all right, in other words, that's a better place to be more stable. Now if you take a look at two carbons sitting next to each other—okay, so we'll draw another ring, we'll put a carbon there, and one, two, three, four, this ring is a little bit messed up, you can deal with that. All right, this carbon here has four electrons in its outer shell. This one has four electrons in its outer shell. Neither one is going to steal from the other. So they tend to form bonds between themselves called covalent bonds, and in these covalent bonds, they tend to share these electrons and form these chains of carbon. So for example, what we would get would be something like this. This carbon would share an electron with this carbon and form a bond there, and these three would be out here: one, two, three, one, two, three. We would represent this with a line like so. That's a covalent bond between two carbons. Now that sets up a situation where you can form molecules bonding to molecules bonding to molecules. Let me show you what I mean.

Let's go back to this glucose molecule right here. Imagine this glucose molecule being able to bond with another glucose molecule. So I'm going to draw this, and I'm going to draw it like this. So here's a glucose molecule, like so, or any what we call monosaccharide. It could be glucose; there's other ones like that. Simple sugars, we call these. Now imagine that this—and this is a carbon, remember that—imagine that this carbon, instead of sitting here like itself, could bond to another carbon right next to it. Think of this. We are going to start forming really big chains of these things like so. So that carbon could bond to that carbon, and that carbon could bond to another carbon, and so we start to get what is a very interesting effect here. Each of these is called, now in sugars, each of these is called a mono (one) saccharide (sugar). By itself, so ignore the bond, saccharide. I want you to imagine that it bonds to another one right here. Now there's two of them. So what do we have? We have a disaccharide, and then we eventually get to three or four, and we call that a polysaccharide. You've heard of these things; I know you have. So this is the way all life works. We start with these monomers, which could be one amino acid, one glucose, one fructose. We put a bunch of them together, and that gives polymers, and that is how organic molecules bond together to form what's sitting in your chair.