Carbohydrates are essential macromolecules composed only of three different chemical elements: carbon (C), oxygen (O) and hydrogen (H). The chemical formula for carbohydrates is Cm(H2O)n, where “m” and “n” represent numbers which can be different from one another. However, it is important to note that there are some exceptions to this formula being used to represent a carbohydrate. For instance the carbohydrate component of DNA does not follow this common formula pattern.
Carbohydrates are also commonly referred to as saccharides which are representative of sugars and starches. In terms of human nutrition, carbohydrates are important for energy and are continually stored within the liver and muscles for later use. Two different chemical compounds, ketones and aldehydes comprise these saccharides and can be classified into 4 different groups:
1. Monosaccharides: These are the simplest types of sugars and cannot be broken down (metabolized) any further. Glucose, galactose and fructose are all examples of monosaccharides
2. Disaccharides: These compounds are composed of two monosaccharides which are bonded together. For example, sucrose is formed when fructose and glucose molecules are bonded together and maltose is a disaccharide composed of two glucose molecules.
3. Oligosaccharides: These compounds are a type of polymer made of many small monosaccharides bonded together, usually 2-9 units. These types of molecules are usually found within a cell’s plasma membrane or as a component of another molecule, such as a side chain on glycoproteins.
4. Polysaccharides: These compounds are composed of more than two monosaccharides. Polysaccharides are polymers which can be formed as chains which can be either branched or unbranched (straight line). Polysaccharides act as a food storage component in both animals and plants and also can act as a structural component commonly in plants. Glycogen and starches are storage polysaccharides, whereas chitin and cellulose are structural polysaccharides.