Enzymes are biological catalysts that speed up the rate of reaction. In the absence of an enzyme it might take forever to complete any metabolic process.
Enzymes are proteins in nature with 3D configuration that is formed by formation of multiple bonds within the structure. By the end of reaction enzymes remain unchanged and can be utilized for the next chemical reaction.
Mechanism of action of enzymes
Mechanism of enzyme action can be understood by the LOCK AND KEY model. As only a specific key can open a specific lock similarly only a specific enzyme can catalyse the reaction for a specific substrate.
Enzymes can be seen as locks that have specific sites known as active sites. This is where substrate comes and bind due to surface complementarity. Once a substrate binds to an enzyme, an enzyme-substrate complex is formed. Enzyme then catalyses the reaction and product is formed that is released however the enzyme remain unaltered. Therefore a small amount of enzymes can bring about a large amount of chemical reactions.