Enzymes are proteins that function as catalysts for chemical reactions, increasing the rate of reactions without being consumed themselves. Enzymes are vital to the most basic reactions of life. Enzymes aren’t consumed in reactions because they do not actually “add” energy to the reaction itself, they only decrease the energy activation level for chemical reactions. Enzymes are highly specialized and only certain enzymes will catalyze certain chemical reactions. All enzymes have an active site, which is where a substrate (the reactant an enzyme acts on) binds to. Once it has bound to the substrate, the active site undergoes an induced fit that strains substrate bonds. Enzymes are affected by cellular environments in terms of PH, temperature, concentrations of substrates, and other factors. These variables make homeostasis important so as to allow enzymes to function. Enzymes also have to worry about inhibitors, which inhibit their reactions. Competitive inhibitors bind to the active site of an enzyme and block it. Non-competitive inhibitors bind somewhere else on the enzyme and change the shape of the active site, so as to not allow it to bind to its substrate. However, inhibitors can also be used by the body to limit excessive enzyme activity through methods like feedback inhibition. In the image above hydrogen peroxide, which tends to break down into oxygen and water, is mixed with yeast. The presence of catalase (an enzyme that breaks down hydrogen peroxide into water and oxygen much faster) in the yeast causes this reaction to occur much faster. The increased speed of this reaction leads to the explosive growth of oxygen bubbles seen above.