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Elements of Life Overview

Hey everybody, welcome back. It is your AP Bio teacher, Mr. Poser. We're covering our second topic of our first unit on chemistry of life and the second topic in overall AP Biology, and this is on elements of life. So we will discuss, well, what we're getting into for the rest of this unit are the four main types of biomolecules, how they're formed, what they're made of, what their properties are, what they do, all that kind of stuff. So that'll be the focus of the rest of this unit. But today we have to talk about elements and particularly carbon and the other elements that help make up biological life and a few other things that have to contribute to the wide variety of biomolecules.

What you are made of, you are really made of atoms, you're made of compounds, you're made of lots of different types of molecules. And that's what the point that we're trying to get at here is that what is able to make life function, including you, is a huge, unbelievably mind-boggling variety of molecules. And we're going to hopefully gain an appreciation for that through the course of this video and through the course of this unit. But in fact, all of the living things that have ever existed are all made of the same elements. So living things need to constantly exchange matter with the environment. So you are truly, you may have heard of this in another context before, but you are truly a product of your environment. The same atoms that make up the ground and the air and the grass eventually are the same atoms that make up you. So living things need to constantly be exchanging waste and nutrients with the environment through several different processes that we'll discuss over the course of this class. But if living things aren't exchanging energy and aren't exchanging matter with the environment, then there can be no life. All right, that's just not how it's going to work at all.

So chemicals that make up living things are carbon-based. The number one atom that's going to be the main atom of all living things is in fact carbon. And in fact, a whole field of chemistry. And these are going to be classes that if you decide to pursue a biology major or a chemistry major or any kind of major having to do with biology, you're going to have to take classes on organic chemistry. And organic chemistry is chemistry that is focused solely on molecules, particularly molecules that are found in living things, but molecules that are made of carbon or have carbon as a primary component. All right. So carbon, it's the main, the main player here as far as molecules of life.

You are mostly carbon besides your water which we maybe consider inorganic because it not made of carbon. Besides your water, carbon is your main thing. Most of your body mass besides water is carbon. And there's a really, really good reason for that. Carbon can form an enormous variety of complex organic compounds. And as I just said, those are compounds containing carbon. So you are made up of organic matter. That means it's carbon-based. You are a carbon-based life form. You might have heard of that in a sci-fi movie or something before. But each carbon atom can form up to four covalent bonds. So we're bringing back a little chemistry again here. But carbon has four valence electrons in its outer shell. That's ringing some bells, right? And because of that, carbon can form up to four covalent bonds, or it can form two double bonds, or it can form a double bond and two single bonds. But anyway, any way you put it, carbon can form a lot of different bonds, which makes it perfect for a building block for building these really, really, really big molecules, like proteins. They're actually huge, right? They're pretty big for molecules. But imagine, like, I don't know, a Lego piece or something like that that's got four different attachment points. That's the one that you're going to be, you know, basing your molecule or molecule, basing your structure off of, right? The one that has the most attachment points. You're going to put it right in the center so you can make as complex of a structure as possible. I don't know. Maybe that's the way I played with Legos or like those little K'nex or whatever, right? Oh, yeah, K'nex. That's a good one.

But anyway, yeah. So here's a type of molecule that I'd like you to know. Hydrocarbons. Hydro is a prefix for hydrogen. And then carbon, you know, carbon. So hydrocarbons are molecules that are only made up of carbon and hydrogen. And those can be pretty significant in organic chemistry as well. I drew one down here. This molecule is called methane which is actually a greenhouse gas but i drew it there because a it's simple and b it really illustrates how carbon can form four different covalent bonds so i could link another carbon here another carbon here another carbon here another carbon here and we can make this huge array of well complex molecules a huge array of hydrocarbons if we wanted to even so yeah carbon is really really good at bonding with a lot of different things so i'm going to move my face here all right so what we're going to be covering in 1.4 and 1.5 and partially in 1.6 are these four main classes of biomolecules and out of all the enormous variety of biomolecules that make you up and make life functional we can group them into four main categories and those or carbohydrates, proteins, lipids, and nucleic acids. You might have seen some of these on a nutrition label before, and I'll talk about that another time. But carbohydrates, proteins, lipids, and nucleic acids. And the elements that make up carbohydrates are carbon hydrogen and O which stands for of course oxygen. Proteins are consistent of mostly carbon hydrogen oxygen and then there some nitrogen and S stands for sulfur. Okay so some proteins have well most proteins have sulfur in them. Lipids are composed of carbon, hydrogen, and oxygen, and lipids are, you know, like your fats and oils and your steroids, that kind of stuff. And nucleic acids, so talking about DNA and RNA, those are made of carbon, hydrogen, oxygen, nitrogen, and P stands for phosphorus. So phosphorus is actually a main component in what we call the backbone of nucleic acids, but we'll cover that more later.

So another thing I want to talk about today, now that we know what kinds of elements make up those biomolecules and thus make up you, we want to talk about a little bit more about how these molecules get so much variety. And one of those ways is through the configuration of the atoms themselves. Now, two different molecules, or two molecules can have the same number of carbons and hydrogens and whatever. They can have the same exact chemical formula, but have two completely different purposes within like the human body or within a living thing. How is that possible? Well, it's because of the arrangement of those carbon atoms or of those hydrogen atoms, for example. And those molecules, if they have the same formula, if they have the same number of carbons, hydrogen, oxygens, whatever, but they're different, they're called isomers. And isomers are compounds with the same numbers of types of atoms but have different structures. And there's three different types of isomers that we're going to discuss to wrap up this video. So the way they're configured can make these molecules even more different.

So this, for example, is an example of structural isomers. Pretend I have, so I didn't want to take all the time to put all the H's there, but pretend I have four carbons, hydrocarbon made up of four carbons, and the way you can arrange them, you can have them put in a line like this, or you can have them in like this T shape. And if we were to put all the hydrogens there and count them all up and write a chemical formula for each one of these molecules, it would end up being the exact same. But they're not the same molecule, just based on the configuration of those carbons. So those are what we call structural isomers. They're different arrangements of atoms. Now, where it gets a little more complicated is when we get into what are called cis-trans isomers. And those are isomers that have a different arrangement of atoms due to double bonds. Okay, so now, a little background on covalent bonds here. A single bond like this one is going to be much more flexible, and it's going to be able to move around much more than, say, a double bond. Okay, so remember, carbon can form four bonds, right? So one, two, three, four. But a double bond is going to be more rigid. It's going to be stuck much more than say a single bond. So there much less room for variation if there a double bond. Okay so now X is just you know, it's not an element. Obviously, there's not an element that has a chemical symbol of X. But let's just say X is like, I don't know, some nitrogen or maybe an amine group or something like that. This is what we call a trans isomer here. A trans isomer is when we have two of the same compound on different sides of that double bond. But cis is when they are on the same side of the hydrogen bond. So here's cis. Cis means same. Trans means, well, different or very. okay so uh trans means it is you know it's on two different sides cis means it's on the same side okay um so that's another type of isomer and then there's one more and honestly i can't really show you how well this works uh or how these work as isomers without a 3d model so i kind of and that's kind of impossible right now uh if we had if we had the tools in order to you know build the model of this, and I currently don't right now, then I could show you what these are, but our third type of isomer that we're going to talk about, now pronounce this with me, they're called enantiomers, enantiomers are isomers that are mirror images of one another due to carbon being bonded to four different things, okay, so this image up here, okay, we see that this, oh, it's what we call a central carbon here, is bonded to, it's got one bond to a hydrogen, one bond to an OH are what's called a hydroxyl group. We have another bond to a CH3, and then we have another bond to a what's called a carboxyl group. But either way, this carbon, both of these molecules, the carbon is bonded to all four of the same things. However, these are still isomers. They're going to have the same chemical formula, but they're going to be different shapes because they're what are called mirror images of one another. And the way I learned this is that you gotta think about your hands, right? So look at your hands, right? Your hands are mirror images of one another, okay? I can't just put my hands over each other and they're going to match like this, okay? Because they're mirror images of each other. They're kind of like enantiomers here, okay? But if I put them apart like this, they look exactly the same, right? But they're not, okay? So your hands are kind of like mirror images of one another. they can't really fold over perfectly on themselves. Even if I put them together like this, they're not the same. So that's what an anti-emerge has to do with. All right, so if that was a lot, I apologize. Maybe I ranted a little bit, but that's it for 1.2. Let me know if you have any questions. We'll see you next time. And where's my stop button?