Although every enzyme performs a different reaction on different substrates, they all go through the same general steps in accomplishing their reaction. These general steps include substrate binding, formation of the enzyme-substrate complex, product formation and dissociation, and enzyme recovery. Like all catalysts, enzymes are unchanged by the overall reaction. Now let's look at each step in more detail. The first step in any enzymatic reaction is the binding of the substrate by the enzyme. The enzyme includes an active site that can accommodate the size, shape, and electron configuration of its substrate or substrates. According to the induced-fit model of enzyme-substrate interaction, a perfect fit does not form until the enzyme and substrate bind bind to form an enzyme-substrate complex. After the substrate has bound in the active site, the enzyme-substrate complex is formed. The shape of the enzyme may change to allow for an efficient chemical reaction, and amino acids may accept or donate protons or electrons to facilitate the chemical reaction. Once the enzyme-substrate complex has formed and any reactive groups have moved to the right position, the reaction proceeds and products are formed. The products dissociate rapidly, leaving an empty active site. After the products leave the active site, the enzyme returns to its original configuration. Any groups that donated or accepted protons or electrons are also returned to their original state. Like all catalysts, the enzyme is unchanged by the overall reaction.