Block C Lecture 3 - Factors Affecting Enzyme Activity Flashcards
What is Arrhenius’s equation, and what does it describe?
k=A.e^ -Ea/RT
where k is the rate constant,
A is the “pre-exponential factor”,
Ea is the activation energy (J/mol),
R is the gas constant and
T is the temperature (kelvin)
It describes how the rate constant (k) of a reaction depends on temperature (T) and activation energy (Ea).
(Slide 9)
How can the activation energy by calculated if you determine the value of the rate constant (k) at several temperatures?
The Arrhenius equation can be converted to the linear form, ln k = -Ea/R .1/T + lnA
y = ax + b
lnk (y axis) can then be plotted against 1/T, with the slope generated being -Ea/R.
Since we know R (gas constant), Ea can be calculated
(Slide 10)
What does permanent denaturation of an enzyme lead to?
Loss of the active site shape, loss of binding efficiency and activity, losing their catalytic activity permanently
(Slides 11 and 12)
What happens when the temperature is below the optimum temperature?
The activity of the enzyme increases as a function of the temperature due to the Arrhenius equation
(Activity increases with temperature until it hits the optimum)
(Slide 12)
How can changing the pH result in denaturation of the enzyme?
As the shape of the enzyme depends on the tertiary structure which is held together by weak bonds such as hydrogen bonds between side chains.
Changing pH can cause these side chains to ionise which results in the loss of hydrogen bonding and denaturation of the enzyme
(Slide 14)
What can changing the pH affect (other than denaturing the enzyme)?
The binding affinity / catalytic activity of the enzyme
Substrate ionisation
(Slide 15)
What shape does a graph of the enzyme activity as a function of the pH form?
A bell shape with an optimum pH (where activity is at its highest)
(Slide 16)
