Why do humans need carbohydrates?

(Q&A by Rachel Lord)

Carbohydrates are compounds made up of oxygen, hydrogen, and carbon. Carbohydrates are either simple sugars or polymers (long chains) of simple sugar molecules. Glucose and fructose are good examples of simple sugars. Simple sugars can also be combined to produce sugars that are more complex. Table sugar is one such an example; it is a combination of fructose and glucose.
Carbohydrates are important to humans because they are our main source of energy. When the body breaks down carbohydrates into glucose and then combines glucose with oxygen to form carbon dioxide and water, a huge amount of energy is released. This energy can be used immediately. If not needed immediately, the sugar can be stored as glycogen, a polymer of glucose. Plants store carbohydrates in the form of starch

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