They are molecules made of PROTEIN and are found in every living cell,
from simple bacteria and yeast, to the most complex animal or plant.
Because they are proteins they are very sensitive to changes in
temperature or pH (see point 6), and also to the presence of INHIBITORS like
Enzymes are biological CATALYSTS - i.e. they are needed in small amounts
to speed up the rate of reaction without being changed themselves.
Enzymes have a special area on them called the ACTIVE SITE – this is where
the chemical reaction with the SUBSTRATE takes place
The ‘LOCK AND KEY’ model explains this:
2H20 + O2
Q10 = 2 "For every 10°C rise in temperature, the rate of
reaction approximately doubles". This is because the enzymes receive more
KINETIC ENERGY, therefore there is more chance of collision with
a substrate molecule.
The OPTIMUM temperature is the temperature at which reactions proceed the
fastest ( the same applies to ‘optimum pH’)
After the optimum has been reached enzyme structure is rapidly destroyed –
this is called DENATURING. (not ‘killed’, ‘dead’, etc)
Enzyme names end with –ASE
e.g.. Catalase, Amylase, Lipase, Maltase. The
exception is PEPSIN (actually a protease enzyme) that coverts proteins
to polypeptides in the stomach.
Questions about enzymes in the exam will be found in the DIGESTION topic
and the RESPIRATION topic mainly.