Sugars are composed of carbon, hydrogen, and oxygen atoms joined together to form one or more rings. There are many different types of sugar whose names may be familiar to you (glucose, fructose, lactose). The table sugar you might add to your coffee is called sucrose. Sucrose is actually a combination of two simple sugars: glucose and fructose. The sugars ribose and deoxyribose are essential parts of nucleic acids (discussed next).