starch

So starch, starch is a what we call a polysaccharide. So poly means many, uh, and saccharide, like we already know, means sugar. So it's a poly sac, alright. And it means it's got many individual sugar monomers all hooked together. And it's a, and this is a polymer that uses glucose as its individual monomer, its building blocks. So you can see here there's lots and lots of individ of green hexagons that you know used to be separated and they used to be individual glucoses and now they're all hooked together in a chain and to make a long chain molecule, a long polysaccharide. And this is starch.

So, um, if I was going to send you to the grocery store and ask you to bring me back something that had a lot of starch in it, think about what you might purchase. Or there's multiple things you could choose from. What would you buy? Um, you might buy, I guess, cornstarch. That's an easy out. That's a pure starch. But you, if you don't gonna buy cornstarch, like an actual food item, maybe you'd buy bread, maybe you'd buy flour, maybe you'd buy rice, perhaps you'd buy a potato. All those things have in common, they all are plant coming from plants because plants are the organisms that make starch. Animals cannot make starch. It's made by plants. And we call starch a storage polymer of glucose. So it's a polymer, it's a long chain, and it's a way that plants store their extra glucose that they might have hanging around.

So why would plants have extra glucose? Well, plants are actually amazing organisms and they're actually able to create these glucose rings, these green hexagons, from scratch. They can just take raw materials and hook together a green hexagon or a glucose molecule. Animals cannot do that. We don't know how to do it. It's, um, our bodies can't do it. We rely on plants on planet Earth to put together all the glucose that everything needs. And plants are incredibly good at it. They're really, really efficient at doing this. And this is the process called photosynthesis that we will get into, um, in, uh, unit 3. I realized I wrote that off the chart, so I'm going to write it here. Sorry. It's a storage polymer, alright, for glucose for plants. And it's how plants store their extra glucose.

So what happens in a plant? And let's think about a potato plant, for example. A green potato plant growing in a field in Idaho, uh, has its leaves above the ground in spring and it's got lots of sun and lots of water and it's feeling really happy. And it's built and it's making lots and lots and lots and lots of glucose because it's doing photosynthesis. And it uses some of the glucose for itself to grow bigger, grow more leaves, grow flowers, that kind of stuff. But the, it makes more than it needs. So the extra glucoses that it puts together in its leaves, because that's where this happens, the extra glucose rings get, um, transported down little tubes in the plant, all the way down, down, down through the stem, underground into cells underground where the glucose rings are all hooked together in a long chain. That's the starch. And it's shoved into a cell. And there's tons and tons of tons of cells that all build up and that creates a potato that the plant just kind of hangs off its butt underground. And it's the plant's store of glucose rings, glucose molecules. And it keeps doing that. All the extra sugars, all the extra glucoses that it makes, it sends down to the underground, puts them all together in a long molecule of starch, shoves it in a cell, and adds it into another potato. And the plant keeps building these potatoes underground, which are the store for all the extra sugar that it built that it didn't need right then.

So then the summer comes, the fall comes, and the weather get bad and the above ground parts of the potato plant get frozen and they die. So the plant has no way of making food because it can't see sunlight, it has no green leaves, it can't do photosynthesis. But it's okay because stored underground in those potatoes are all the extra sugar molecules, all the extra glucose molecules that the plant made when times were good in the summer. And it can use those stores of glucose throughout the winter to survive. And then when the weather gets warm again and the plant can sense that, it can then use those starch molecules to release glucose back to the plant and the plant can sprout up again and start growing. A farmer basically interrupts that cycle and says, "Hey, I'm gonna dig up that potato and take that store of glucose for me and I'm gonna eat it." Um, so when you eat a potato, you are eating this molecule here that the plant put together and it's stored underground for itself for when the weather got bad. You've kind of gone in and said, "Hey, thank you very much. I'm gonna take that from me." And we eat it in our body. And then we use the all the sugars that are stored inside that long chain.

The one thing that's important to note about starch is if we go to the small, this diagram down here, when you put all these glucose rings together side by side, there's four of them here, uh, they are linked together. I like to describe it as holding hands facing down. They're not holding hands up, they're holding hands down because you can see all these oxygens, the, the bond here between the rings is like sort of facing down, right? Why is that important? The reason that's important is that in our intestines, in our digestive system, mammals, we have the ability to break this bond. We can do hydrolysis of this bond and separate this out. So even though you eat a potato, it does not taste sweet because it's, it's got starch molecules in it. And starch does not taste sweet. It's not the same as glucose. It's a different kind of molecule. They're all hooked together. Um, when it gets into your stomach and the hydrolysis and the digestion happens, you're able to break these, um, linkages, the holding hands down linkages. And every time you do a hydrolysis here, you release a glucose. And you cut here and you release a glucose. And you cut here and release a glucose. So although starch is not glucose and doesn't taste sweet, in your body, the molecule gets broken down back into the individual glucoses that it was initially made from. And that's one of the reasons why people with diabetes, who have to be very tight and closely watch their sugar intake, it's not just the sweet tasting sugars that they have to watch. They also have to watch for molecules like starch, like carbs, basically bread, wheat, rice, pasta, all that kind of stuff. When they eat that, it will still increase their blood sugar. It may take a little bit longer because the sugar isn't directly glucose already, but by the time this molecule hits their stomach and gets broken down, then sugar will be released into their bloodstream just the same as if they had eaten a teaspoon of glucose or or even sucrose, like table sugar. So that is starch, a storage polymer of glucose that's found and produced by plants.