The two basic types of metabolism are known as anabolism and catabolism. Anabolism is also usually referred to as “building up”, while catabolism is usually described as “breaking down”. In an anabolic reaction, there is a use up of energy. They are referred to as being endergonic. In the case of anabolic reactions, there exist the joining together of smaller molecules to form larger ones.
For example, the joining together of amino acids to form dipeptides, the joining together of small sugar molecules to form disaccharides, and the reaction of glycerol with fatty acids to form lipids. On the contrary, there is a giving out of energy in catabolic reactions, and they are referred to as being exergonic.
In the case of catabolic reactions, there is a breaking down of larger molecules into smaller ones. In brief, the reverse or hydrolysis reaction of the condensation reactions given above are examples of catabolic reactions.