Starch is a polymer made by plants to store energy.

You see, plants need energy to grow and grow and grow. They use energy from sunlight to make a simple sugar, glucose.Plants make polymers - starch - out of extra glucose, so it"s right there when they need it. Click on the figures to the right and below to pop-up 3D models to view.

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Click the picture to see a 3-d interactive version of starch.
Wouldn"t it be great for a whole bunch of glucose molecules to be together in one package? Well, plants thought that was a cool idea. They hook glucose molecules all together in such a way that the long chain curls all around and forms a big globby polymer. That"s starch! Whenever the plant needs energy, it can chomp a little glucose off of the starch. Chomp! mmmmm!
Here is a short section of starch, with only 4 glucose molecules. Starch can also have a lot of branches. Each branch is a short chain made from glucoses, and each branch can make more branches. Crazy, huh?

Another good thing about starch: Each little glucose likes to have water all around it. That can be really hard on the plant. In a starch polymer, the glucose units have other glucose units around them, and that works just as well as water. So, the plant doesn"t need so much water, and everybody"s happy!


Hey, what about us?!

We need glucose for energy, too. You even need energy to think! When you eat starchy food, special proteins called enzymes (which are also polymers, by the way) break starch down into glucose, soyour body can burn it for energy. This starts happening right in your mouth! There"s an enzyme in your spit (yep, your spit!) that starts to cut up the starch. Check out this link to see how you can taste this enzyme working. Foods that have a lot of starch include: grains (like rice and wheat), corn, and potatoes.


Our bodies can"t make starch - only plants make starch. We have two ways of storing excess glucose. I"m sure you know about this first way! If you eat a lot more starch than you need for energy, then your body can store it by turning it into fat. (That"s just one job that your liver does.)

But what if glucose is needed RIGHT NOW? Like if you have to get up and run run run?!!! There"s no time to break down fat! You need glucose NOW!! How do our bodies store glucose so that it"s ready fast? Click here for the answer.

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Starch is very similar to cellulose. But cellulose is a fiber that you can"t digest. The thing that makes these two polymers different is simply how the glucose molecules are put together in the polymer chain. Click here to learn more about how plants make starch, and how it differs from cellulose.

Starch has some uses other than food. It"s used in pressing clothes to keep them from wrinkling. It"s also used to make foam packing "peanuts". This packing is better for the earth than Styrofoam packing. It dissolves in water, and it"s biodegradable (meaning that little critters can eat it!)

But back to food -- did you know that corn starch can be used to make gravy and pudding thick? Starch can also be modified, that is, the structure can be changed, so that it can hold more water, or in some way be better for cooking or flavor. A kind of starch that can hang on to water better, or hold water longer, will help keep cake from getting stale.