 Why hello there. Today we're going to talk about chemistry. And you might be wondering, dude, this is a biology class. Why are we going to talk about chemistry? And first of all, I would love it if you actually took a second to think about, come up with an idea in your brain for why. Why would we spend an entire lecture and in some courses, multiple lectures on chemistry in a biology class? And hopefully your little brain is working to think, we've actually already answered that question. And the answer lies in this little bad boy. Does this look familiar? Yeah, totally. This is the hierarchical... the hierarchical organization of living structures. If you remember when we started making our lists of all the hierarchical levels of organization in living systems, what? We had this huge stack of levels that were most certainly not alive. And those levels are based on chemistry. So today's task, okay, cool. Today's task will focus on these levels of organization. And hopefully you get the idea that, dude, we have to understand atoms and molecules and, dude, the little subatomic particles that make up the atoms and molecules in order to understand how organelles work or cells. And that's what we're going to talk about next. So having a sense of chemistry, first of all, is really important. So that's awesome. You know why I care about chemistry. What's an atom? There it is. That is a totally inaccurate image of an atom. Atoms are composed of subatomic particles. We are going to talk about three of those subatomic particles, but I'm not kidding you, atoms are tiny. Like, they're crazy tiny. They're tinier. Like, 602 sextillion hydrogen atoms weigh the same as a paperclip. 602 sextillion, that's not trillion, or quadrillion, or quintillion. That's sextillion with like 23 zeros after the six. What? They're tiny. And they don't weigh very much, because most of them is open space. We're going to talk about each of the subatomic particles inside our atom. And atom is the building block of all matter. Everything around us, including the air, including the table, including my fantabulous pen, everything is made out of atoms. And we're going to be looking in this class at cellular processes that enable life or based on the movement of different kinds of atoms, which is like, oh, shockingly cool. So let's get started. Let's start by looking at one flavor of subatomic particle, and that is the proton.