?The enzyme amylase will catalyze the hydrolysis of starch to maltose when the pH is near 7.0. But
when the HCl is added to the solution the amylase will be denatured which results in the enzyme
being deactivated. The iodine serves as an indicator for the presence of starch. Iodine (I2) will
reach with iodide ion to produce the I3- ion. This ion will form a dark blue complex with the
Like most chemical reactions, the rate of an enzyme-catalyzed reaction increases as the
temperature is raised. A ten degree Centigrade rise in temperature will increase the activity of
most enzymes by 50 to 100%. Variations in reaction temperature as small as 1 or 2 degrees may
introduce changes of 10 to 20% in the results. In the case of enzymatic reactions, this is
complicated by the fact that many enzymes are adversely affected by high temperatures. As shown
in Figure 13, the reaction rate increases with temperature to a maximum level, then abruptly
declines with further increase of temperature. Because most animal enzymes rapidly become
denatured at temperatures above 40?C, most enzyme determinations are carried out somewhat
below that temperature.
Over a period of time, enzymes will be deactivated at even moderate temperatures. Storage of
enzymes at 5?C or below is generally the most suitable. Some enzymes lose their activity when
. As amylase breaks down starch, less and less starch will be present and the color of the solution
(if iodine is added) will become lighter and lighter.
Enzymes are biological molecules that catalyze many different chemical reactions. With few
exceptions, all enzymes are proteins and each enzyme is specific to a certain chemical reaction.
Enzymes must maintain a specific three dimensional structure in order to function properly. If an
enzyme’s structure is altered (by heat or harsh chemicals) it may not function at all. This
breakdown (denaturation) of an enzyme’s