OC3 - role of conformational changes

Question 1

allosteric enzymes

Answer 1

enzymes that have an additional binding site for effector molecules (modulators) other than the active site

Question 2

modulators

Answer 2

a molecule which binds to the allosteric site
binding of a modulator induces a conformational change in the enzyme which affects the shape of the active site and the affinity for the substrate.
do not bind permanently, when their concentration falls they are released from the allosteric sites

Question 3

positive modulator

Answer 3

binds to the allosteric site and increases the affinity of the enzyme for its substrate

Question 4

negative modulator

Answer 4

binds to a different allosteric site and reduces the affinity of the enzyme for its substrate.

Question 5

haemoglobin and oxygen

Answer 5

oxygen acts as a positive modulator for haemoglobin, the binding and release of oxygen in haemoglobin shows co-operativity - changes in binding of oxygen at one subunit alters the affinity of the remaining subunits for oxygen.
initially there is a weak affinity for oxygen and the binding of the first oxygen molecule is slow, the binding of the first oxygen molecule induces a conformational change in the second haem subunit which increases affinity for the second oxygen molecule, increasing speed of binding. this repeats for the third and fourth subunit.