Only when the enzyme binds to the enzyme is the active site the correct shape to catalyse the reaction. As the products of the reaction form, they fit the active site less well and fall away from it. Without the substrate, the enzyme reverts to its relaxed state, until the next substrate comes along.
Catalase:.
Catalase is an enzyme which catalyses the decomposition of Hydrogen Peroxide, as shown in the equation;.
.
Catalase.
2H2O2 2H2O + O2.
Catalase.
Hydrogen Peroxide Water + Oxygen.
It splits the Hydrogen Peroxide into non-toxic water and oxygen gas. It is one of the fastest acting enzymes known. At 0oC one molecule of catalase can decompose 40,000 molecules of Hydrogen Peroxide a second. The optimum pH of catalase is pH7.60, under these conditions the maximum rate of reaction occurs. When the pH is altered above or below this the rate of the enzyme activity diminishes. The pH change leads to an alteration in enzyme shape, particularly at the active site. If an enzyme encounters extremes of pH, it will be denatured. At temperatures of 40oC and over the enzyme is denatured and so is irreversibly damaged. This is because the structure of the enzyme molecule is vibrating so quickly due to kinetic energy from the heat, that some of the bonds holding the enzyme molecule in its precise shape begin to break. Hydrogen Peroxide is a toxic by product of metabolism in certain plant and animal cells. Liver this is the site where all toxins and poisonous substances are absorbed and detoxified. Catalase is found in the liver and in certain plant cells such as the cells in a potato. I will be using liver as a source of catalase during this experiment.