The effect of enzyme concentration on the rate of a controlled enzymatic reactionEnzymes are protein molecules, which can be defined as biological catalysts, which alter the rate of a reaction without the enzymes undergoing change themselves. Enzymes are usually specific to a single reaction. Enzymes are globular proteins with the helix wrapped in a precise three-dimensional tertiary structure, with hydrophilic R groups held by four different types of bonds:1. Hydrogen2. Disulfide3. Ionic4. Hydrophilic/hydrophobic enzymes have an active site, a region, usually a cleft or depression to which another molecule can bind. This specific molecule is the substrate of enzymes. The precise shape of the active site allows the substrate to bind perfectly to the active site. This is known as the "Lock and Key system". The combined structure is defined as the enzyme-substrate complex. As the enzyme-substrate complex forms, the interaction between the R groups of the enzyme and the substrate atoms may break down, or encourage the formation of bonds in the substrate molecule, forming one or more products. Enzymes work by reducing the activation energy. In terms of the enzyme-substrate complex, this happens by placing tension on the original bonds, through the enzyme and substrate molecules bonding together, and the way the substrate is held allows the molecules to react more easily. In turn, this reduces the activation energy, allowing the reaction to proceed faster. The course of an enzyme-controlled reaction is quite simplistic in theory. The speed of this reaction is always faster at the beginning. This short period is called the initial reaction rate and lasts about 30 seconds. When studying the effect of enzyme concentration it is more appropriate to look at the initial rate of reaction, since once the reaction is underway, the amount of substrate available in the reaction begins to vary, the substrate is converted into products at a rate different, all depending on the concentration.