Enzymes are used to speed up biochemical reactions that occur within the body. They act as a catalyst for specific substances and therefore reduce activation energy. A catalyst is a substance that speeds up the rate of a chemical reaction without being used up or altered, and therefore can be used repeatedly. Enzymes are also used to control cell metabolism by regulating the rate of biochemical reactions, this is because the amount of enzyme in a solution determines how fast a reaction can occur.
An enzyme consists of complex chemicals that form precise, tertiary and quaternary protein structure consisting of long, linear chains of amino acids linked together with polypeptide bonds, which fold in such a way that they form a three dimensional, globular shape which is held together by hydrogen bonds and ionic forces. The structure has an area on its surface called the active site, which is used to bond to specific substances. The particular shape of each enzyme is specific to the type of reaction it will catalyse, making them very selective and usually only able to catalyse one specific reaction.
The substance that an enzyme acts on is known as the substrate. The substrate forms a temporary binding with the active site, creating an enzyme-substrate complex which causes the substrate to react faster. Once the substrate has been broken down into a different substance this end substance is called the product. When the product has been produced the enzymes active site becomes free and will bind to another substrate and continue repeating the same process.
The way in which enzymes work is currently explained through two theoretical models. The first theory is called the lock-and-key hypothesis. This idea assumes that because particles within the cell are constantly moving that the enzyme collides with the substrate and binds together due to the specific shape of the active site being relative to shape of the substrate molecule. This particular...