Page 106 - Demo 1

People who are lactose intolerant are unable to digest lactose, the sugar in
milk, because their intesnal cells do not produce lactase, the enzyme needed
to break down lactose into its glucose components. This deficiency shows how
the lack of just one enzyme in the human body can lead to problems. A person
who is lactose intolerant can swallow a drop of lactase prior to drinking milk
and the problem is solved. Other enzyme deficiencies, however, are not nearly
as easy to fix.
FACTORS THAT AFFECT ENZYME ACTIVITY

Enzyme acvity is affected by any change in condion that alters the three-
dimensional shape of the enzyme. Factors such as pH, temperature, and
substrate concentraon have a major influence on the acon of enzymes.

pH Factor

Each enzyme works within quite a small pH
range. There is a pH at which its acvity is
greatest, referred to as the opmal pH. This is
because changes in pH can make and break
intramolecular and intermolecular bonds,
altering the shape of the enzyme and,
therefore, its effecveness. Extreme pH values,
acidic or basic, can make enzymes denature.
Most human enzymes, such as the protein-
degrading enzyme trypsin, work best within
the range of pH 6 to 8. The digesve enzyme
pepsin, however, is able to funcon in highly
acidic condions, like that in the stomach.

Temperature

As the temperature rises, reacng molecules
have more and more kinec energy. This
increases the chances of a successful collision
and so the rate of reacon increases. There is a
certain temperature at which an enzyme's
catalyc acvity is at its greatest, the opmal
temperature. Optimal temperature is usually
o
around human body temperature (37.5 C) for
the enzymes in human cells.

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