Carbohydrates contain carbon plus hydrogen and oxygen in the same ratio, and the general formula is CnH2nOn. Sugar, starches, and fibre are three types of carbohydrates we eat as food and are found mostly in grain products, vegetables, and fruits. The family of sugars is made up of many substances. The term "sugar" refers specifically to ‘sucrose’, the main product of photosynthesis. The term ‘sugars’, however, can also refer to sucrose, in addition to a variety of other sugars found in nature.

"Saccharides" are the basic building blocks of sugars and carbohydrates, which are often classified according to the number of saccharide units they contain. Monosaccharides, for example, contain a single saccharide unit, whereas disaccharides contain two. Glucose, fructose, and galactose are all examples of monosaccharides. When two monosaccharides are joined together chemically, a disaccharide is created. Sucrose, C12H22O11, is a disaccharide, made up of glucose and fructose.

sucrose molecule

The monosaccharides glucose and fructose and the disaccharides sucrose, maltose and lactose all occur naturally. Glucose and fructose are found in honey and fruits, whereas sucrose (also referred to as table sugar) is found in molasses, maple syrup and in fruits and vegetables. Lactose is found in milk. Maltose is present in sprouting grains, malted milk, malted cereals, and some corn syrups.

Monosaccharide   Monosaccharide   Disaccharide
Glucose + Fructose Sucrose
Glucose + Galactose Lactose
Glucose + Glucose Maltose

Polysaccharides are another type of carbohydrate which are large molecules consisting of many saccharide units (>9) in long chains of many repeating units. Starches and fibre are among this class of carbohydrates, with starch being the most abundant in our diet. Thousands of glucose units are strung together to comprise a single starch molecule.

branching of Polysaccharides

To learn more, see our resource Clips on Sugars - Facts on Sugars