2. Enzymes are protein molecules that are able to
catalyse a biological reaction.
3. Each type of enzyme is highly specific for only
one type of a reaction
With the use of an enzyme the rate of a
particular reaction can increase by a factor
greater than 108
They work by providing an alternative
pathway with a lower activation energy
More reactant molecules then have the
necessary minimum activation energy
4. The specificity of the enzyme depends on their
tertiary and quaternary structure.
The substrate (reactant molecule) binds to a
part of the enzyme known as the active site
The active site is able to change shape allowing
the substrate to fit effectively and this is known
as the induced fit theory
5.
6. Inhibitors are substances that slow down the
rate of an enzyme catalysed reaction
Competitive inhibitors resemble the substrate in
shape but they are unable to react
They occupy the active site making it less
accessible to the substrate
As the concentration of the substrate molecules
increases the effect of the competitive inhibitors
decreases
8. Non-competitive inhibitors bind to the enzyme
but not to the active site
The enzyme then changes shape and the
substrates are no longer able to bind
With this type of inhibitor increasing the
concentration of the substrate molecules will
have no effect as the non-competitive inhibitors
don’t bind to the active site
11. At low substrate concentrations the rate of the
reaction is proportional to the concentration of
the substrate
At high substrate concentrations the rate of the
reaction reaches a maximum point known as
Vmax
This means that that at low substrate
concentrations there are enough active sites for
the substrates to bind and react
When all the active sites are used the enzyme is
not able to work any faster
12. This constant Km is the concentration of the
substrate at half of the Vmax
It is always the same for a particular enzyme
with a particular substrate
It indicates whether the enzyme functions
appropriately at low substrate concentrations
or whether high substrate concentrations are
needed for the efficient catalysis
Lower Km → more efficient enzyme
13.
14. Say That Again Please
http://www.youtube.com/watch?v=q94TCTSXyv8&context=C47b5c79ADvjVQa
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15. Competitive vs Non-competitive
Competitive inhibitor Non-competitive
Blocks active sites Enzyme changes shape
Same Vmax Smaller Vmax
Larger Km Same Km
16. An increase in temperature at first increases the rate
of the reaction until the optimum temperature is
reached (usually 40°C)
Until then more reactants posses the necessary
activation energy to react
After the optimum temperature is reached the
enzyme starts to denaturate as the bonds holding
the structure together break
At certain pH values there is a change in the charge
of the amino acid which affects the bond and alters
the structure of the enzyme making it inactive
17. Heavy metals “poison” the enzyme
They react with the –SH group and replace the
hydrogen atom with a heavy metal atom, or
ion altering once more the structure of the
enzyme