The basic units of carbohydrates are sugars, or monosaccharides. The basic units of these sugars are pentose and hexose molecules, with five and six carbon atoms respectively. Carbohydrates contain hydrogen, oxygen and carbon and can be further broken down into these molecules within the human body.
Carbohydrates are an essential part of the human diet and should comprise approximately 50 to 60 percent of a person's daily food intake. They are a source of energy for the human body because they can be easily broken down within the body to provide a burst of energy. After consuming carbohydrates, the body converts the carbohydrates into simple sugars, or monosaccharides that can be used by the body's cells for energy and fuel.