Monomers are small units which are the components of larger molecules, examples include monosaccharides such as glucose, amino acids and nucleotides. Polymers are molecules made from many monomers joined together.

Monomers are joined by a chemical bond in a condensation reaction whereby a water molecule is eliminated. Hydrolysis is the opposite of a condensation reaction and is when water is added to break a chemical bond between two molecules.

Carbohydrates

Carbohydrates are molecules which consist only of carbon, hydrogen and oxygen and they are long chains of sugar units called saccharides. A single monomer is called a monosaccharide with a pair of monomers being called a disaccharide. Combining many monosaccharides results in the formation of a polysaccharide. These are all joined together with a glycosidic bond formed in a condensation reaction.

Monosaccharides

alpha

beta

Glucose is a monosaccharide containing six carbon atoms in each molecule, and is the main substrate for respiration and therefore of great importance. It has two isomers - alpha and beta glucose with structures being seen on the right.

Common monosaccharides include glucose, galactose and fructose. These are typically sweet tasting, soluble

substances which have the general formula (CH20)n where n can any number from three to seven.

Disaccharides:

Two monosaccharides can join together in a condensation reaction to form a disaccharide. In this process a molecule of water is produced. The diagram below shows the formation of a 1,4 glycosidic bond between two alpha glucose molecules in order to form a molecule of maltose.