What is an enzyme? and why are they so important for reactions to take place?

An enzyme is a type of protein which we call a biological catalyst. In biology, a catalyst is a chemical which helps speed up reactions without being used up itself. Therefore, if you add 2ml of an enzyme to a reaction, you will still have 2ml of that same enzyme left at the end of the reaction. These catalysts remain unchanged after the chemical process has taken place and are therefore free to catalyse more reactions. Cells contain hundreds of different enzymes, each carrying out a different reactions.These biological catalysts are crucial to life because without them, reactions would take place at a very slow rate. Therefore, the enzymes are needed to ensure that essential biological processes such as DNA synthesis occur at a rate fast enough for life to go on. For example, DNA polymerase is an enzyme that speeds up DNA synthesis.