chitin

This polysaccharide that we're going to talk about here is called chitin. I think you can see there a small chitin. It looks like chitin, that's kind of how it's spelt, but you say chitin.

Um, chitin is another structural polymer. So what that means is this molecule is used to create shape or structure in organisms. And the kind of organisms that make chitin are fungi, that's why we have this picture down here, and also um arthropods. Arthropods are bugs, insects, and crustacea. So um butterflies, bugs, beetles, things like that, and also shrimp and crabs, things with this kind of exoskeleton. All right.

So, and the um fungi make chitin for their cell walls. So fungi are a kind of organism that has a cell wall, a little bit like plants, but they're not related to plants at all, even though people think they are. They're actually more closely related to animals. Fungi are because they, and they make this molecule chitin for their cell walls.

Um, so chitin again uses um glucose hooked together to build this long chain structure. Um, but it's a slightly different glucose. So, oh, there's no such thing as different glucose, it's a, it's a modified glucose. So here is glucose up here, but in normally, down here, there would be an OH. Regular glucose would have an OH here, but this monomer has this different group hanging down here, NH C double bond O CH3.

So what happens in fungi and in certain animals, these arthropods, is that they make a bunch of this molecule here, and then they hook them all together in a long line like here. Now, I couldn't find a good picture of chitin, but this, uh, up here, this is one chain. These sort of squished bow tie looking things are supposed to be the hexagons of glucose. It's not great, but these are the glucoses, they're all hooked together in a chain. Um, and then here's the bit that dangles down. This bit here is this bit here. And so you build all the, the animal or fungi builds a whole bunch of chains like that. There's one there, and there's one there. And then they line those chains up, and the bit that dangles down connects to the one underneath it, to the chain underneath it. So you have these permanent connections between all these rows of glucoses. They're, they're stacked up this way, and then they're connected this way. So it creates a very strong molecular structure.

And chitin is really interesting in biology because it can be used, it can be molded into lots of different shapes. So you can make it in very, very thin layers, and something as delicate as a butterfly's wing, that's made out of chitin, a thin, thin layer of chitin. Or it can be laid down incredibly thick, and it makes a hard armor, just like on a crab. So if anybody has eaten crab and they've accidentally crunched a piece or lobster legs or whatever, they've accidentally crunched a piece of the shell, you know how hard that is and how pointy it can be. That's all made out of chitin, molded into these crazy shapes, pinchers and rigidy bits and stuff like that. So you can make fine, delicate stuff, you can make really thick coats, things like that, or you can make the walls of fungi.

The other interesting thing about chitin is that since it can be so strong yet so flexible, and we use it to make sutures. So that's what this picture is all about. Um, so in the olden days, uh, they used to use something called cat gut to make sutures. Cat gut. Now, it's not the guts of cats, although it sounds like it should be, it's actually the guts of sheep or goats. They would take the intestines, lay them out and dry them, and then cut them into like sort of long thin strips, and it's very, very strong. I know it sounds kind of weird right now, but that was what we used to use to, um, for suturing. Uh, but that held a problem because it was from another animal, like a mammal, that, uh, it, so many people were allergic to the, to that, um, to that material. So it wasn't good for sutures.

So nowadays, we discovered that chitin, because it's simply made of modified glucose, nothing's really allergic to glucose. So we are able to use this monomer, create these long threads, they're very strong, but they're also very flexible, and they make it makes a great material for suturing. Um, these aren't the, the dissolvable ones, but anyway, chitin sutures. So that is another structural polymer made by fungi and, um, arthropods like spiders, bugs, crustacea, shrimps, and lobsters, that kind of stuff, um, to keep structure in shape.