Enzyme kinetics is a branch of biophysical chemistry focusing on studying the rates of enzyme-catalysed reactions. Enzymes act as highly effective catalysts, characterized by the formation of a complex between the substrate and the enzyme. The enzyme possesses an active site which allows it to stabilize the transition state of the substrate. A substrate can bind to the active site of the enzyme, which is complementary to the three-dimensional structure of a specific substrate, to provide a new, lower-energy reaction path. This reaction process can be affected by certain variables, resulting in a faster or slower conversion rate of the substrate to the product. Two mathematical techniques can be used to determine values in enzyme kinetics. The Michaelis-Menten equation is used to describe the rate of enzymatic reactions. When a reaction is catalysed by an enzyme, it usually portrays a hyperbolic relationship between the reaction rate and the concentration of the substrate. As the concentration of the substrate increases, with a fixed concentration of enzyme, it will approach the characteristic maximum reaction rate. Another technique that can be used is the Eadie-Hofstee diagram, which plots the reaction rate against the ratio between the rate and substrate concentration, producing a linear graph. This graph can be used to easily derive the values of the maximum reaction rate (Vmax) and the concentration of substrate required for half the maximum rate (km). The maximum reaction rate is affected by the pH of the solution. All enzymes have an optimum pH or pH range at which they have their maximal activity. At a higher or lower pH this activity decreases, and extreme deviations from their optimum generally results in complete loss of activity. Amino acid side chains in an enzyme may only act as weak acids and bases if they maintain a certain state of ionization. At different pH values this ionization state is changed, limiting the ability for the enzyme to catalyze reactions effectively.