Biology IGCSE 0610
Chapter 3: Enzymes
Enzymes
Enzymes are proteins that Act as biological catalyst, that speed up
chemical reactions by lowering activation energy.
They are specific in shape as they have specific active site.
Why enzyme have specific active site?
Each enzyme has a specific active site that is complementary to a
specific substrate, fitting like a lock and key to form an enzyme-
substrate complex. Under optimum temperature and pH, the substrate
is converted into products, which leave the active site while the
enzyme remains unchanged.
Type of enzymes
➢Starch + amylase = Maltose
➢Maltose + Maltase = Glucose
➢Proteins + protease/pepsin/trypsin = Amino acids
➢Lipids + lipase = Fatty acids and glycerol
Effect of temperature
on enzyme activity
Describe:
As temperature increase,
the rate of enzyme activity
increased reaching the
Peak, above temperature
degree enzyme activity decreased.
Explain:
As temperature increases
Kinetic energy increases
More chance of successful collisions
More chance to fit like lock and key
More enzyme substrate complex.
Above optimum enzyme got denatured and
active site lost its shape
Enzyme and substrate is no longer
complementary
Effect of pH on
enzyme activity
100
Describe:
As pH increase from 0 , the rate of enzyme
activity
increase from 0 a.u to 100 a.u at pH 7 , above
pH 7,
enzyme activity decreased reaching 0 a.u at
pH 14
Explain:
pH7 is the optimum pH where maximum
enzyme activity
pH near the optimum, the enzyme is still
working
pH far away from optimum, the enzyme 0
denatured active site lost 0 7 14
its shape enzyme and substrate is no longer
complementary, so no
enzyme substrate complex
Enzyme concentration is
limiting factor
Enzyme concentration
As concentration of enzyme increases the
rate of enzyme activity increase ( enzyme
concentration is a limiting factor).
After a while the rate of reaction starts to Enzyme concentration is
decrease until enzyme concentration is no
longer is a limiting factor. no longer limiting factor
Substrate concentration is a
limiting factor
Substrate concentration
As the concentration of substrate increases,
the rate of enzyme activity increases because
more substrate molecules are available for
the enzymes to work on. At first, the enzyme
concentration is the limiting factor, meaning
that the more substrate you add, the faster
the reaction becomes. Substrate concentration
However, after a certain point, the rate of is no longer a limiting
reaction starts to level off because all the factor
enzyme molecules are fully occupied and
cannot handle any more substrate. At this
stage, adding more substrate won't increase
the reaction rate, and the enzyme
concentration is no longer the limiting factor.
Role of enzyme n biological washing powder
Biological washing powder contains enzymes that break down large
complex insoluble food stains into small simple soluble molecules to
be easily washed out by water, as amylase enzyme breaks down large
complex insoluble starch stains into small simple soluble sugars to be
easily washed out by water, as protease enzyme breaks down large
complex insoluble proteins into small simple soluble amino acids to be
easily washed out by water, as lipase enzyme breaks down large
complex insoluble lipid molecules into small simple fatty acids and
glycerol to be easily washed out by water.
Role of enzymes in baby food
• Baby food contains enzymes that break down large complex insoluble
food molecules into small simple soluble molecules to be easily
absorbed in the blood, as amylase breaks down large complex
insoluble starch molecules to small simple soluble sugars for
respiration and energy/ATP release, as protease breaks down large
complex insoluble proteins to small simple soluble amino acids for
growth and tissue repair, as lipase breaks down large complex
insoluble lipid molecules to small simple fatty acids and glycerol for
thermal and electrical insulation and cell membrane formation.
