Introduction: Carbohydrates are one of the most important macromolecules in an organism's body. While they are sometimes used as structural components, their primary function is to provide the body with energy. Imagine this - it is the middle of the afternoon and you are feeling a bit rundown. There is a candy bar in your bag you have been saving for just this occasion. A short time after you eat it, you feel a burst of energy. How did this happen? Well, your body is able to break down the sugars in the candy fairly quickly, thereby releasing their energy. Now, something to realize here is that the sugar in candy is only good for a quick burst of energy. If you are looking for a more long-term solution to the afternoon doldrums, a piece of fruit is a better option. This is because the sugars in here take longer to break down, so they are able to maintain your body for a longer time.

Like all organic molecules, carbohydrates are composed of monomers that make up larger molecules. These monomers are called monosaccharides and are usually in the shape of a ring (see the diagram of a glucose molecule left).

Carbohydrates can range from a single ring (such as the glucose molecules in the diagram) to having many rings and branches (such as in the polysaccharide cellulose, which makes up the cell walls in plants).

Directions for this Lesson: Answer the practice questions and then watch the videos to learn more about the structure and function of carbohydrates.