ENZYMES
ENZYMES
A
type of Protein
MADE
UP OF WHAT?
A folded chain of amino acids
 In

living things they act as
Catalysts
 WHICH MEANS :
 molecules that are used to speed up a
chemical reaction. They take part in
the reaction; BUT the enzyme remains
unchanged and can be used again.
LABEL THE PARTS
Products
Substrate (Reactant)
Active Site
The enzyme does not change
in the reaction. Therefore
an enzyme can be used
over and over again.
ENZYMES
Are
needed for all chemical
reactions including
Dehydration synthesis and
 Hydrolysis

Provide
the right “setting” for
the chemical reaction
Enzyme Activity Demo
ENZYMES BREAKDOWN OR BUILDUP
CATABOLISM
ANABOLISM
USE A NEW SET OF WORDS FOR WHAT WE
HAVE ALREADY TALKED ABOUT
Relate catabolism and anabolism
to dehydration synthesis and
hydrolysis…
HOW DO ENZYMES WORK?

Orient the molecules correctly

See the animation! Compare enzyme to
no enzyme.
 Increase
the likelihood a reaction
will occur!

This lowers the Activation Energy
(Ea) required for a reaction to
occur
ACTIVATION ENERGY
Enzymes
make it easier for
substrates to react

This is how the activation energy is
lowered
Activation

energy
The amount of energy needed to
convert reactants into products
This is the “cost of the reaction”
The enzyme is a “coupon”
ENERGY PLOT
Progress of the reaction
CHEMICAL REACTIONS
 Some
reactions require energy
input
 Some chemical reactions release
energy

Both require activation energy..so look at
where the products are on the energy
axis.

What has more energy, product or
reactants?
THE CATALYTIC CYCLE OF AN ENZYME
Breakdown of Sucrose to Glucose and Fructose
Using Sucrase
ENZYMES EXHIBIT SPECIFICITY
Look at the shape of the
substrate and the active site

An enzyme is not only substrate specific, but it
can only catalyze a reaction in ONE direction.
So, it either builds up, or breaks down
…but not both
SPECIFICITY OF ENZYMES
 Enzymes
are EXTREMELY specific
 There
is a unique enzyme for
EVERY substrate that reacts in the
body
 Each
enzyme’s active site will ONLY
fit one specific substrate
LOCK AND KEY (ACTUAL SHAPE)
INDUCED FIT THEORY -ENZYMES
ACTIVE SITE
part of an enzyme
where substrates
bind and undergo a
chemical reaction
If this location is
changed (damaged,
mutated, etc. , the
reaction cannot
take place.
WHAT IMPACTS ENZYMES

Temperature
All enzymes have an optimal (a “best”)
temperature.
 Exceeding the optimal may cause
enzyme inactivation (enzyme doesn’t
work) due to breakage of bonds in the
3D structure


RESULT: Denaturation (breaking down
3D structure to a polypeptide
doesn’t work
WHAT IMPACTS ENZYMES
pH
 changing
the concentration of H+
interferes with the bonds holding
the protein in its folded shape.
 Raising
or lowering pH above or
below optimal will cause
denaturation.
OPTIMAL PH
pH
is?
changing
the concentration of
H+ interferes with the bonds
holding the protein in its folded
shape.
ENZYMES HAVE SPECIFIC PH
DENATURATION
Caused by high temperatures and pH changes
HOW FAST AN ENZYME WORKS ALSO
DEPENDS ON:

The ratio of the the substrate to
the enzyme. Look at the
graph…what does it tell us about
“velocity” (speed of the reaction)
and substrate concentration?
 Concentration

of the Enzyme
Concentration of the Substrate
(what it is putting together or
taking apart).
SATURATION CURVE
What does this tell us? Why does this happen ?
COENZYMES AND COFACTORS
Coenzymes

Organic molecules such as vitamins
Cofactors

Inorganic molecules or ions such as Zn and Cu
Both attach to enzymes and improve
chances that substrate will bind to the
enzyme.

ENZYME INHIBITION
Inhibit:
shut down or suppress
Can be caused by outside
molecule – drugs/poisons
Can be caused by inside
molecule if your body wants to
temporarily shut down a
reaction
 Why waste the energy?
COMPETITIVE INHIBITION
molecules
that are similar in shape
to the substrate bind to the active
site and block the substrate; No
chemical reaction can happen
Examples:
Drugs and Insecticides
NON-COMPETITIVE INHIBITION
molecule
binds to a part of the
enzyme and alters the shape of the
active site; No chemical reaction
INTERPRETING ENZYME GRAPHS
 What
is the optimum temperature
for this enzyme?
INTERPRETING ENZYME GRAPHS
 Would
this make a good human enzyme?