 So let's remind ourselves of protein structure. Of course, this is all review. Proteins, what are the building blocks of protein? Let's write it down. Protein, essentially a protein is nothing more than a string of what? Amino acids, right? Totally cool. A protein is just a whole bunch of amino acids put together. In fact, the primary structure of a protein is the order of the amino acids in Wendy land and other lands. This is a common annotation. That means primary. So primary structure of a protein is just the order that the amino acids are strung up in. You remember your A's, T's, G's and C's. Do you remember that? T, A from Bio 1, T. And the fact that every three nucleotides in a DNA molecule will code for one amino acid. Do you remember that? Please tell me that you're like, oh, sure, Wendy. Okay, well, the bottom line is that your DNA contains the information that you need to build your protein because the order of the bases in the DNA tells you which amino acid to stick in order. And then you, not in yellow, are going to put a little bond, a chemical bond between those amino acids. Now in Wendy land, the amino acids are little beads, right? Can you imagine like we string the little beads together and the order that we string them together in is going to matter to the end product. So the primary structure of a protein is just the order that we put these in. We could put purple, red, purple like that. You can even see, oh, I just tried to put it, never mind. You could put them in this order or you could put them in that order. You're going to get a different protein depending on what order you put them in. So the order matters. That's your primary structure. And then your secondary structure happens when a string of amino acids, the primary structure, the string of amino acids like folds on itself. And hopefully you're like, dude, what the hell is she talking about? Look. Look at the Wendy land analogy. Here are my beads. These are my amino acids. And I've strung them together. So the pipe cleaner actually represents like chemical bonds between my amino acids. And the string of amino acids will actually fold on itself. And depending on the amino acids involved, that will determine what kind of folding you have. Old boy Linus Pauling back in the day, he was like the king of figuring out structural, like who would ever figure this out? That your proteins can fold in this kind of a shape? And he did this like, I don't know, there's this awesome video of him talking about how one day he was sick at home, laying in bed, lying in bed. And he started thinking, God, there's got to be a way that the amino acids fold. And he figured out the alpha helix by folding a piece of paper and figuring out which bonds can form where. Fantastic. Thanks Linus. That was cool. If I had another kid, I'd name him Linus. I'm not having another kid. So that is your secondary structure. There's two, we can form into an alpha helix or we can form into a beta pleated sheet, but it's just a folding of that original primary structure. Does that work for you? Guess what? Of course, there's tertiary structure. It's a tertiary-ly structured protein. All we do is fold on ourselves again. And the folding varies because the shape is going to be variable depending on the amino acids that are in there. So you actually fold a second time, fold again. Now, I could give you beads and pipe cleaners and if you were my kids, you'd be like, oh, life is so good, we've got all these cool art supplies that you could make all sorts of different shaped proteins. I mean, it's not hard to think about folding these pipe cleaners into different shapes and we could even do something, we could even make rules that the yellow amino acid has to form a bond with the black amino acid so they're going to stick together and that's how we're going to end up determining what kind of shape we're going to have with our tertiary structure. But it works, right? So imagine that we're going to fold ourselves all up and we're going to get a three-dimensional shape. That's our tertiary structure. Is that it? No. You've got to have a quaternary structure, yo. I mean, it's not done until you've got your quaternary structure. Look, here, let's fold it again. Here's another beta-pleated sheet, secondary structure. And then let's fold that on itself. Tertiary structure, guess what quaternary structure is? Let's stick two of them together. They stick together and now we have two protein blobs with unique shape that are stuck together. Does that work for you? It's pretty fantastic. So, oops, this is so exciting. The quaternary structure is when two tertiary proteins, one, there's one, they form a chemical bond between them. Somehow, they actually stick together. Hemoglobin, you know you love hemoglobin, we all do. Hemoglobin is made up of four proteins. So it has quaternary structure. And the four proteins are connected to each other. And that's how you get one molecule of hemoglobin to connect millions on each red blood cell. It's ridiculous. Are you happy? I'm totally happy. This is your review of protein structure. Now, let's build some stuff. Let's build some stuff that in ourselves can do something for us when it changes shape. Remind yourself, what kinds of things cause these little protein structures to change shape? Well, if we add heat, that's going to change their shape. If we add another molecule, like the scissor molecule, if that scissor molecule comes in here and adds, whoa, that was crazy, it changes its shape. When the scissor molecule falls off, whoa, it went back to the way that it was. I know you want me to bring these to class so that you can play. I might. All right, let's talk about what we can build with these proteins.