All organisms rely on enzymes to catalyze chemical reactions. An enzyme is a biological catalyst that increases the rate of chemical reactions by lowering the level of activation energy necessary to start the reaction. Without enzymes, many of the chemical reactions that occur within living things would proceed too slowly to be useful. Enzymes speed up these reactions by bringing the reactants into close proximity and facilitating their interaction.
Liver contains a specific enzyme called catalase. When hydrogen peroxide (H202) is added to liver, a chemical reaction happens which results in the production of oxygen gas (O2) and liquid water (H20).