Zusammenfassung der Ressource
OCR - A-Level -
Biology - Factors
Affecting Rate of
Reaction
- Temperature
- As the temperature
increases, both the
enzyme and the
substrate gain more
kinetic energy
- This means they move
faster. As a result, they
are more likely to
collide, resulting in
more collisions in a set
amount of time.
- The more they collide,
the more likely they
are to form
enzyme-substrate
complexes, up to a
point.
- After this point (the
optimum), some weaker
bonds, such as hydrogen
and ionic bonds, that hold
the tertiary structure of
the active site together
may break.
- As a result, the active
site changes shape so
the substrate is no
longer complementary.
This means the reaction
cannot proceed and the
enzyme is denatured.
- pH
- Hydrogen ions are
attracted to negatively
charged ions. Hydrogen
bonds and ionic bonds hold
the active site together.
- Excess hydrogen ions interfere
with the bonds, resulting in
the active site changing shape.
This means that the number
of E-S complexes will be
decreased.
- This will also mean that
the charges will be
altered on the active
site. The binding of
substrates molecules to
the active site will be
interfered with.
- The number of
acidic or basic
R-groups affects
the optimum pH.
- Enzyme
concentration
- Cells are constantly
recycling old enzyme
molecules to avoid
harming the cell
- More enzymes mean
more active sites are
available. Additionally,
there will be more
successful collisions
- More collisions mean
more E-S complexes
forming, so rate of
reaction increases.
- After the concentration
is increased further, the
reaction reaches the
maximum rate. The extra
enzyme molecules will
not have substrates free
to fit the active site.
- To avoid this,
increase the
substrate
concentration.
- Substrate
concentration
- Without a substrate,
the enzyme-catalysed
reaction cannot
proceed.
- As the concentration
of the substrate
increases, there are
more substrate
molecules.
- This means more
E-S complexes can
be formed, and
more product
molecules.
- After the concentration is
increased further, the
reaction reaches the
maximum rate. All of the
enzymes' active sites are
occupied with substrate
molecules.
- To avoid this,
increase the
enzyme
concentration.