Sol Song, Chelsea Ryu
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
Catalase is a type of enzyme that catalyzes the decomposition of hydrogen peroxide. The
reaction is as follows: 2H
O + O
(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.
To compare the action of catalse to a non-protein catalyst under different conditions.
Materials and Equipment
3% hydrogen peroxide
2 stirring rods
fresh or frozen liver
250mL beaker, graduated cylinder
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.
Put on lab apron and draw your own symbol on each test tube as an