factors affecting enzymes Flashcards
What factors affect enzymes?
Temperature
pH
Concentration of enzyme
Concentration of substrate
Measuring the initial rate of reaction
A line is drawn at a tangent
to the initial slope of the
graph.
A convenient time is
chosen (e.g., 20 seconds)
and a vertical line is drawn
up from this point.
Initial rate of reaction
In any reaction, the initial rate of reaction is fastest.
At the beginning of the reaction the enzyme and substrate
molecules have a greater chance of successfully colliding.
As the reaction proceeds, substrate is used up and so the
frequency of successful collisions decreases.
The initial rate gives the maximum reaction rate under those
conditions.
The effect of temperature on enzymes
At low temperatures the enzyme
and substrate have reduced
kinetic energy and so fewer
enzyme-substrate complexes
form (reversible).
The rate of enzyme-controlled
reactions increases as
temperature increases up to a
maximum called the optimum
temperature.
high temp: The enzyme vibrates.
Some of the bonds (hydrogen and
ionic) that hold the tertiary
structure together may break.
As the active site shape changes,
the substrate will not fit as well and
the rate of reaction will decrease.
More heat causes an irreversible
change in the shape of the active
site so that it is no longer
complementary to the substrate.
The enzyme is denatured.
How do changes in pH affect enzymes?
H+ are attracted to negative charges.
Excess H+ will interfere with hydrogen and ionic bonds that
hold the tertiary structure of an enzyme.
If the shape of the active site changes, the substrate will not fit
well, and the rate of reaction will decrease.
If the normal optimum pH is restored, the H bonds can reform,
and the active site’s shape will be restored.
At extremes of pH, the enzyme’s active site may be
permanently changed (denatured).
—
In highly acidic or highly
alkaline conditions, H+ or
OH- ions will interact with
amino acids in the enzyme
which causes hydrogen
bonds to break and the
shape of the enzyme to be
altered.
This causes the enzyme to
denature.
how can buffer resist change in ph
A buffer can accept or
donate hydrogen ions to
control the amount of
hydrogen ions present in
the blood.
What will happen to the rate of reaction as the substrate concentration
increases?
The rate increases.
This is because more ES complexes form.
More EP complexes form.
More product molecules are formed.
Substrate concentration is the limiting factor because as it increases, the
rate of reaction increases.
active site saturation,
all active sites will be in use.
What will happen to the rate of reaction as the enzyme concentration
increases?
The rate increases.
This is because more active sites become available.
More ES complexes form.
More EP complexes form.
More product molecules are formed.
Enzyme concentration is the limiting factor because as it increases,
the rate of reaction increases.
