Condensation Reaction

A condensation reaction occurs when two molecules join together and a molecule of water is released. One of these molecules must have a hydroxyl group to be released, while the other must have a lone hydrogen atom to be released. 

For example, during the reaction of amino acids, two amino acids come together to form a dipeptide through a peptide bond. One amino acid loses its OH group while the other loses its H group, thereby releasing a water molecule (H-OH) as the product of this reaction.