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

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

7. Competitive inhibition

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

9. Non-competitive inhibition

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

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

18. Effect of temperature and pH on
rate of enzyme activity