Simple sugars, also called a monosaccharide, are molecules, such as glucose or fructose, that bond together to create more complex sugars, such as maltose or starch. Glucose is the simple sugar that is used as energy in the body.
Simple sugars consist of between three and seven carbon atoms. Other elements present in sugars are hydrogen and oxygen. In the human body, glucose is the most popular form of simple sugar.
By combining with oxygen, glucose produces the energy cells need to run certain processes. Glucose in the presence of oxygen yields carbon dioxide and water. This reaction releases 2,870 kilojoules of energy. In the body, glucose is normally stored in the form of glycogen, which is a polysaccharide made of chains of the monosaccharide glucose.