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Biology 12 Sol Song, Chelsea Ryu Oct.20/ 2009 Enzymes Introduction: All living organisms require enzymes for efficient and fast metabolic reactions. An enzyme is found to be water-soluble protein, with the exception of hydrophobic lipoprotein in mitochondria. Some enzymes are entirely protein; others consist of two parts: an apoenzyme that is protein, and cofactor or coenzyme that is non-protein. Cofactor is inorganic, but coenzyme is organic. Catalase is a type of enzyme that catalyzes the decomposition of hydrogen peroxide. The reaction is as follows: 2H 2 O 2--> 2H 2 O + O 2 (the substrate is hydrogen peroxide and the products are the two harmless molecules, water and oxygen). The presence of catalase is crucial to break down the poisonous hydrogen peroxide. If the catalase does not catalyze this harmful chemical, the cells will die. It is mostly found in the peroxisomes and glycoxisomes of plants, such as potatoes, and in the liver and kidney tissues of mammals. In this lab, a potato, liver, and manganese dioxide will be used to study catalase. Is the action of catalase changed under different conditions? If the catalse exists in potato and liver cells, it will react differently when it is reused, and the amount of substrate, particle size, and temperature are changed. Since an enzyme changes its shape, or become denatured, under high temperatures and extremes of pH, it stops function at the certain conditions. Also, if a cell increases in the surface area to volume ratio, it generally speeds up its reaction, for more surface area means more contact with other reactants to initiate the reaction. The higher concentration of substrate is another factor that increases the rate of reaction. However, the reaction speeds up only until all the enzymes are saturated, or completely filled with substrates. Purpose: To compare the action of catalse to a non-protein catalyst under different conditions. Procedure: Materials and Equipment 3% hydrogen peroxide scalpel manganese dioxide 2 stirring rods fresh or frozen liver hotplate potato 250mL beaker, graduated cylinder ice test tubes, test tube rack, test tube tongs fine clean sand lab apron, water soluble marker CAUTION: *Hydrogen peroxide is an aggressive oxidizer that may corrode many materials, even human skin. Do not get any in your mouth. Wash away any spills or splashes with plenty of water. Call your teacher. *Manganese dioxide is also a harmful oxidizer that can cause fire with combustible material. It is harmful to respiratory and nervous systems. In case of contact with skin or eyes, rinse immediately with plenty of water and call your teacher. 1. Put on lab apron and draw your own symbol on each test tube as an indicator.... View Full Document

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