Ch 2.3: Chemical Reactions: Bringing the Boom (or Not)

Those valence electrons, hanging out on the outskirts of the atom, those fuckers are the important ones. They maintain the perimeter and they’re going to be the first ones to encounter another atom when they meet one. So when we discuss chemical reactions, what we’re really discussing is the action of one atom’s valence electrons in regards to those of another. Sometimes those interactions can make things go boom, other times they go sizzle, and still other times they seem to do nothing at all. But no matter the type of reaction that is occuring, really the only thing that’s happening is the atoms are rearranging how they’re grouped together. We’re not creating or destroying matter, just mixing it up. Conservation of mass if you want to sound like a smart ass.

We could spend a lifetime talking about chemical reactions and chemical bonds but we’re not because again, Biology for Bastards. Now in order for these reactions to take place, we have to put some energy into it at first. This is known as the activation energy and the best way to think of it is as gambling, which, as bastards, we do. You go to the casino, get the free drinks, and sit down at a machine. You can’t start playing right away, first you have to put money into it. Same thing with reactions. Some reactions are cheap, those are our penny slots, while others take a shit ton of energy to get going and are equivalent to our high rollers. No matter the energy required, you have to get to that amount before the reaction takes place. You can’t have half the energy and get half the reaction, it doesn’t work that way. You can’t play the ten dollar slots if you have five dollars. Just won’t work. Now sometimes, we can get away with cheating and using a catalyst to lower the cost. A catalyst is nothing more than something that speeds up a reaction by lowering the activation energy. It’s like having five dollars in free slot play so now you can do that ten dollar slot machine with your five dollars plus the free play cash.

So we’ve discussed what reactions are and how they happen, so now we have to talk about the types of bonds formed when these reactions take place. I know, chemistry kind of sucks and this shit just goes on and on but you’ll see why we’re focused on this at the end of the chapter (when actual biology starts to happen…). Technically there are three types of bonds but we’re not going to worry about one of them because we’re not robots. So ignoring metallic bonds, we have ionic bonds and covalent bonds. Ionic bonds occur when electrons are fully given up by one atom and fully received by another. On the other hand, covalent bonds occur when the electrons are shared by the two atoms. It’s like child custody: ionic is when one parent fully gives up their parental rights to the other and covalent is joint custody.

Just like joint custody doesn’t have to be even, neither does the sharing of electrons in covalent bonds. Sometimes, one atom ends up with custody of the electrons more than the other and when this occurs, a polar covalent bond is formed. (The opposite of a polar bond is nonpolar...no shit).  They’re called polar because they have a positive end and a negative end, just like a magnet. The negative side is where the electrons tend to hang out more and as a result, the opposite side is a little more positive. Polar bonds are super fucking important in biology because a lot of the elements we deal with (like oxygen…) make polar bonds and as a result, perhaps the most important interactions in biology can occur. What are these nearly mythical interactions that are responsible for keeping your ass alive? Hydrogen bonds. So important they’re called bonds when they aren’t actually sharing or transferring electrons. They’ve been promoted to bond level without doing bond work. They’re hot shit. Hydrogen bonds occur when you get two polar molecules together and the slight negative of one wants to pair up with the slight positive of another. I like to think of them as velcro (hook and loop fasteners if we’re avoiding copyrighted names…) because individually, a hydrogen bond is weak as hell. But when you get a bunch of them together they magically become strong as fuck. Hydrogen bonds help keep proteins together, help your DNA not fall apart and kill you, keep the world from being a giant ball of ice, all sorts of stuff. Like I said, they’re a big fucking deal.

Writer’s Soap Box Moment

You ever just stare at a glass of something with ice in it and wonder why the ice floats? No? Do you realize that the solid of everything else on the planet sinks if you throw it in it’s liquid? Throw a rock into a volcano and it’ll sink. Same thing if you put solid metal into some molten metal, Terminator 2 style, its bye bye T-1000. Not so with water. Water floats on it’s liquid and the way it is able to do so has everything to do with hydrogen bonds. When water is a liquid, the various molecules are drifting past each other fairly quickly, they dont have time to stop and get friendly with their neighboring molecules. But as the temperature drops and they move a little more slowly, they start to notice what’s around them. So around four degrees celsius, a magic event occurs. This is where water is as dense as it will be and as the temperature continues to drop, the molecules begin aligning based on the slightly positive and slightly negative ends and they spread out. Its not dissimilar to being able to tolerate being closer to people when you’re walking through a hallway but you wouldn’t want to be that close to them forever. You’d eventually want to spread out and face your friends. That’s what water does when it freezes and that’s why it floats. Which is a good thing because if it sank, every winter water would freeze and sink, piling up until the entire planet was a giant ice ball. If that happened, we totally we be dead. So thanks hydrogen bonds.