1.8 Enzyme Inhibition - AQA AS/A level biology notes

1.9 Enzyme Inhibition
= substances that directly//indirectly interfere with the functioning of active
site; reducing its activity.

• COMPETITIVE inhibitors = bind to active site
• NON-COMPETITIVE inhibitors = bind to enzyme at another region (not
active site)


Competitive inhibitors:

• Molecular shape similar to substrate
• Allowing them to bind to active site of an enzyme, like a substrate
would.
• Compete for available active sites.

• If substrate concentration is higher -- effect of inhibitor reduced (vice
versa).
• Inhibitor not permanently bound to active site, when leaves, can be
replaced (e.g. by substrate, inhibitor molecules)
• Sooner or later, all substrates occupy an active site, but depending on
inhibitor concentration it may take longer/quicker.

Competitive inhibition e.g.:

1) A respiratory enzyme that acts on succinate (acid).
Malonate acts as the inhibitor --> can inhibit enzyme due to similar
molecular shape.

2) Penicillin can inhibit the enzyme transpeptidase.
(Penicillin irreversibly inhibits the enzyme transpeptidase by reacting
with a serine residue in the transpeptidase. This reaction is irreversible
and so the growth of the bacterial cell wall is inhibited.) -- extra/