CHAPTER 4: ENZYMES
4.1 WHAT ARE ENZYMES?
catalysts made up of
1. Enzymes are organic __________
protein.
2. Enzymes are used to direct and regulate metabolic
_________
in the body of living organisms. These processes
anabolic (building up) and _________
catabolic
involve _________
(breaking down) of organic molecules.
Catabolic
Substrate
Anabolic
EXAMPLES OF ENZYME-CATALYZED PROCESS
Food molecule such as carbohydrates and
simpler
proteins need to be converted into _________
soluble in water and
substances, which are ________
diffusible
______________
(small enough to pass through
the cell membrane)
energy
 Oxidation of glucose to release ________,
______________
carbon dioxide and ______________
water
 The cell produces enzyme catalase to catalyst the
breakdown of poisonous hydrogen peroxide into
oxygen
hydrogen
__________
and _______________

4.2 CLASSIFICATION OF ENZYMES
classified according to the
_____________________
they catalyze.
chemical reactions
 2. Some classes of enzymes are:
hydrolase
 a. ________________
 enzyme that catalyze
hydrolysis (breaking down of complex molecules
into simple molecules using water molecules)
amylase
cellulase
 - eg: ____________
hydrolyze starch; ___________
proteases hydrolyze
hydrolyze cellulose; ___________
lipase
proteins; ___________
hydrolyze fats
oxidation - reduction  oxidize food during
 b. ___________________
cellular respiration

1. Enzymes are
LOCK AND KEY HYPOTHESIS
Product
Enzyme-substrate
complex
A specific ________
substrate
molecules arrives at the
____________
of the
active site
enzyme molecules
The ________
enzyme is free to take
another substrate molecule
active site
into its ____________
to
catalyse another reaction
The substrate molecule
binds to the
active
site
_____________
to form
an __________________
Enzyme- substrate
_____________which
is
complex
unstable
_____________
Product
molecules leave the
__________________
of
active site
the enzyme
Enzymes
speed up
_______________
chemical reactions
_____________
and
Substrate
enzyme
concentration
___________ affect
the rate of reaction
Enzymes are
required in
__________
small
amount
Characteristics
of Enzymes
Activity of enzymes
are affected by
pH
________________
Enzymes are
specific
_____________
Activity of enzymes
are affected by
temperature
________________
Enzymes catalyse
reversible
_______________
reactions
Enzymes may need
coenzymes
_______________
for activity
WHAT ARE THE FUNCTIONS OF COENZYMES?
Coenzyme binds to other areas of the enzyme,
changing its shape and allowing the active site
to better fit the substrate.
 The function of the coenzyme is to bring an
added element to the reaction.

THE EFFECT OF PH ON ENZYMES
acidic
Enzyme activity is affected by the ___________
alkaline of liquid surrounding the
and ___________
enzymes
different
 Different enzymes work at _____________
pH
values
alkaline
 Eg: a) Amylase works best in an _____________
medium
 b) Enzymes in the stomach work best in an
acidic
_________
medium
denatured if the medium is
 Enzymes will be ____________
too acidic or alkaline

EFFECT OF TEMPERATURE ON ENZYME ACTIVITY
The optimum temperature of this enzyme is 40oC.
THE EFFECT OF PH ON ENZYMES
acidic
Enzyme activity is affected by the ___________
alkaline of liquid surrounding the
and ___________
enzymes
different
 Different enzymes work at _____________
pH
values
alkaline
 Eg: a) Amylase works best in an _____________
medium
 b) Enzymes in the stomach work best in an
acidic
_________
medium
denatured if the medium is
 Enzymes will be ____________
too acidic or alkaline

EFFECT OF PH ON ENZYME ACTIVITY
- Pepsin
works the best in the acidic condition
- Trypsin works the best in the alkaline condition
EFFECTS OF SUBSTRATE CONCENTRATION ON
RATE OF REACTION
less substrate concentrations, few
At _____
substrates are present.
enzymes
 -There are many ________________
increases in direct
 -Rate of reactions ___________
proportion to the substrate concentration

At a certain substrate concentration, the rate
change
constant and will not _________.
becomes ___________
constant
 - The reaction is at _______________
rate.
 - All the active sites are filled with substrates.
saturated
 - The enzyme molecules are _______________.

high substrate concentrations, there are
At ______
more substrate molecules than enzyme
_________
molecules
active sites are engaged in catalysis of
 - All the _____________
the substrates, an increase in substrate
concentration will not alter the rate of reaction.
constant
The rate of reaction is ________
limiting factor
 - The enzyme concentration is a _______________
increase if the
 - The rate of reaction can only __________
enzyme concentration increases.

EFFECTS OF ENZYME CONCENTRATION ON RATE
OF REACTION
-rate of an enzyme-catalysed reaction is
direct
____________
proportional to the
concentration of enzyme until a maximum rate
 - beyond the maximum rate of reaction, the
concentration of __________
substrate becomes a
limiting factor


- when the enzyme concentration is doubled,
doubled
the rate of reaction will be _____________
Rate of Reaction
4x
2x
1x
Enzyme Concentration