Enzymes are macromolecules and have high molecular weight. There are present numerous active sites on the surface of enzymes where the substrate molecules attach to form an unstable complex. This complex is called an enzyme-substrate complex. It breaks to release the product and enzyme.
By increasing the amount of enzyme, the rate of reaction increases, until the concentration of the substrate becomes a limiting factor. At this stage, the rate of reaction can be increased by increasing the concentration of substrate.
