Carbohydrates in food

Uh, I'm done in. Must have more energy. Now. Sugar or something. Take some veggies instead!

See how energetic my rabbits are. I need fast energy. Not tough grass. And I want to get protein for my muscles. Hmm, maybe I'll devour one of your furry creatures.

Whoa there! What's the fuss? This thing about carbohydrates and energy is not all that complicated. We need energy to: Keep warm Move the muscles Keep the brain going Just like a car, we have to fill up with energy. Not petrol of course...

food! We get energy from - fat... from proteins... and from carbohydrates. Most of us get most of our energy from certain carbohydrates.

There are many kinds of carbohydrate. And all are compounds of the three elements: carbon, hydrogen and oxygen. Here we have a small carbohydrate - with six carbon atoms. It's a type of sugar. And this here is a simple sugar called glucose.

Glucose often forms a circle, like this. But it can also be straight - like this. There is glucose in all plants. Especially in sweet fruits -- like kiwi and banana. And so there is glucose in us humans.

Glucose molecules are small bundles of energy that keep heart and muscles going. But do we have to eat large amounts of glucose to get energy? No, the amazing thing is we can make our own glucose -- from other carbohydrates. There are many different types of carbohydrate. We can divide them into three groups -- according to how long the molecules are.

The shortest we call sugar, as found abundantly in fruit. Then we have slightly longer molecules we call starch. There is a lot of starch in wheat, potatoes, and unripe bananas. Another type of long-chained carbohydrate is called cellulose. Cellulose is in all plants and functions as a kind of building material for them.

For example, there's a great deal of cellulose in nutshell, banana peel - and grass. But there's a problem. The small cells in your body can't take in these large carbohydrates. Instead the cells want the very shortest carbohydrates - glucose. So we must first break down the long carbohydrates into shorter ones.

This already begins in the mouth. As you chew, an enzyme in the saliva breaks down the long carbohydrate molecules. In the stomach, it's too acidic for the enzyme to work well, but... The splitting of the carbohydrate molecules continues in the small intestine. The goal is to break down all the carbohydrates into glucose -- for release into the blood.

Shorter carbohydrates -- like ordinary sugar -- are quick to break down. Longer carbohydrates -- like starch -- take more time. But in the long molecules of cellulose, the bonds are very strong... ... so strong that it's hard to break them apart. But cows, rabbits, and many other animals can break down cellulose in their stomachs.

Despite this, cellulose is important even for us humans. Cellulose in food is also called dietary fibre -- or just fibre. Fibre makes sure the intestines function efficiently. It helps us feel full and satisfied. But it gives us almost no energy.

So, if Jenny needs fast energy, she can eat something sweet -- that can quickly turn into glucose -- to give power to the muscles and brain... ... like a banana - or an apple. But the rabbits can freely eat the grass.