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 starch
molecule. 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 frozen. . 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.