What would happen
to your cells if they made a poisonous chemical? You might think that
they would die. In fact, your cells are
always making poisonous chemicals. They do not die because your cells
use enzymes to break down these poisonous chemicals into harmless substances.
Enzymes are proteins that speed up the rate of reactions that would
otherwise happen more slowly. The enzyme is not altered by the reaction.
hundreds of different enzymes in each of your cells. Each of these
enzymes is responsible for one particular reaction that occurs in the
In this lab, you will study an enzyme that is found in the cells of many living tissues. The name of the enzyme is catalase (KAT-uh-LAYSS); it speeds up a reaction which breaks down hydrogen peroxide, a toxic chemical, into 2 harmless substances--water and oxygen. The reaction is as follows:
2H2O2 ----> 2H2O + O2
This reaction is important to cells because hydrogen peroxide (H2O2) is produced as a byproduct of many normal cellular reactions. If the cells did not break down the hydrogen peroxide, they would be poisoned and die.
For each unit, the number of candidates who achieved a pass grade during the year is divided by the number who sat during the year and this number is expressed as a percentage. The pass rates include all sittings for a unit for the year and include (where applicable), UK sittings, international sittings, in-company sittings. In order to provide the most accurate picture of pass rates and avoid the skewing of data by single events or short-term trends, pass rates are produced and updated annually. The new pass rates replace the oldest set, so that pass rates from the last two years are always shown.