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Organic Compounds

Teacher/Instructor Patrick Roisen
Patrick Roisen

M.Ed., Stanford University
Winner of multiple teaching awards

Patrick has been teaching AP Biology for 14 years and is the winner of multiple teaching awards.

Organic compounds are compounds composed of carbon, hydrogen and often oxygen or nitrogen. Organic compounds are named so because they are associated with living organisms. Several important types of organic compounds include carbohydrates, lipids, nucleic acids and proteins.

One of the more basic ideas in Biological Chemistry is the idea of organic compounds. Now the name organic literally means it's alive. And what scientists found out a long time ago, is a lot of the molecules that are in living creatures are actually based on carbon. And so now we call these carbon-based molecules organic molecules.

Now why is carbon used so much? Carbon is a very useful atom because it can form four bonds and pretty much most of the bonds that it forms are covalent cause it's fairly strong but not too strong in terms of its electoral negativity. So in this example here it's bound to four different elements and each one of these bonds is covalent or polar-covalent.

Now in the big group of organic compounds perhaps the most useful of them are the organic polymers. Now I'll get into what are polymers in just a moment but the four basic groups are the lipids which are things like well fats and waxes. There is proteins which make up things like your muscles, your hair, your finger nails, the front of your eye. A carbohydrate which make up the sugars and the starches that we love to eat and the nucleic acids which makes up those very important molecules called DNA and RNA.

Now a polymer as I mentioned previously, what that is is a long molecule made out of a bunch of smaller molecules called monomers. It's kind of like how a train is actually a long string of train cars that have been hooked together. We call the individual train cars of a polymer monomers like I said. And within the lipids they have different monomers then there are proteins which have different monomers and the carbohydrates and the nucleic acids.

Now I'm going to go ahead and look at how do we link these monomers together? Over here I've drawn a couple of monomers. These would be monosaccharides which are the individual monomers of carbohydrates that when you link them together, two monosaccharides make a disaccharide. More than two, you start getting into, you don't care how many so you just call them many of the saccharides or polysaccharides. So here's one monosaccharide or sugar, here's another monosaccharide. To get them to hook together, what I'm going to do is I'm going to pull off the OH group from here. And I'll just put that over to the side. There's now a bond here that's open to join to this oxygen but it's already got the two bonds that it normally needs to make. So I'll just pull that hydrogen off and now that oxygen will easily bond to that carbon and now I have a disaccharide or dimmer generically. Now you notice I pulled out water from it. What do we call this process? Well, what do you call it when you remove water from something? That's called dehydration. This pen's dying, goodbye. Dehydration, so we poured out our water. And why did we pull out water? We pulled out water in order to make something. Now scientists don't like to use the term "make" so instead they use the term "synthesis" because it sounds cooler and more expensive. So it's called "dehydration synthesis," okay? And all of your organic polymers are made through the same basic process. You pull a hydrogen off of a one monomer, you pull an OH group off of another and they link together like this. So, how do I run this in reverse?

Well, remember I had that water molecule earlier. If only I could break this and put that hydrogen there, let me go ahead and do that. I, no let me just make a really long bond there. So I've broken that off, that means this bond here will break but that carbon right now is unstable. It needs some, what if I add that there. That's it. Now in order to make this happen what did I have to do? I had to break this water in half. What's the rule word that means water, hydro and there is another rule word called lys which means to break or split. Move these out of the way and I just turned that into a process name so it's called "hydrolysis." So hydrolysis is how do we split our polymers back into the monomers that we started with. And that's organic molecules.