MDG S2 Flashcards
Define Allosterism
The binding of a substrate to at one site of a multisubunit protein that influences the subsequent binding of other substrates to other subunits
Give an example of Allosterism
Haemoglobin - when oxygen binds to one subunit, it increases the oxygen affinity of the next subunit
What is competitive inhibition?
Where the inhibitor non-permanently binds to the enzyme at the substrate binding site to lower enzyme activity
How does competitive inhibition affect Vmax and Km?
Vmax is unaffected but Km increases
What is non-competitive inhibition?
Where the inhibitor molecule permanently binds to the enzyme NOT at the substrate binding site to lower enzyme activity
How does non-competitive inhibition affect Km and Vmax?
Km is unaffected but Vmax is reduced
Define Vmax
The maximum velocity of an enzyme catalysed reaction
Define Km
The substrate concentration that will give half Vmax
How does increased concentration of 2,3-BPG affect the oxygen affinity of haemoglobin?
Decreased affinity for oxygen, dissociation curve shifts to the right
How does an increased pH affect the oxygen affinity of haemoglobin?
Increased pH=Decreased [H+] so increased oxygen affinity so the dissociation curve shifts to the left
What are the differences between alpha and beta thalassaemia?
Alpha thalassaemia is fatal and symptoms occur before birth. Beta thalassaemia’s symptoms appear after birth
Why is alpha thalassaemia diagnosed before birth but beta thalassaemia can only be diagnosed after birth?
Foetal haemoglobin is made up of alpha and gamma subunits so beta subunits aren’t produced until after birth, so the defective gene isn’t yet being expressed.
