Carbohydrates perform numerous roles in living organisms. Polysaccharides serve for the storage of energy (e.g., starch and glycogen), and as structural components (e.g., cellulose in plants and chitin in arthropods).

The 5-carbon monosaccharide ribose is an important component of coenzymes (e.g., ATP, FAD, and NAD) and the backbone of the genetic molecule known as RNA. The related deoxyribose is a component of DNA. Saccharides and their derivatives include many other important biomolecules that play key roles in the immune system, fertilization, preventing pathogenesis, blood clotting, and development.

Types of carbohydrates

There are two major types of carbohydrates (or carbs) in foods: simple and complex.

Simple carbohydrates: These are also called simple sugars. Simple sugars are found in refined sugars, like the white sugar you’d find in a sugar bowl. If you have a lollipop, you’re eating simple carbs. But you’ll also find simple sugars in more nutritious foods, such as fruit and milk. It’s better to get your simple sugars from food like fruit and milk. Why? Because sugar isn’t added to these foods and they also contain vitamins, fiber, and important nutrients like calcium. A lollipop has lots of added sugar and doesn’t contain important nutrients.

Complex carbohydrates: These are also called starches. Starches include grain products, such as bread, crackers, pasta, and rice. As with simple sugars, some complex carbohydrate foods are better choices than others. Refined (say: ree-find) grains, such as white flour and white rice, have been processed, which removes nutrients and fiber. But unrefined grains still contain these vitamins and minerals. Unrefined grains also are rich in fiber, which helps your digestive system work well. Fiber helps you feel full, so you are less likely to overeat these foods. That explains why a bowl of oatmeal fills you up better than sugary candy with the same amount of calories as the oatmeal.