Question

7. Write True or False next to each statement:
(a) Enzymes can change the rate of a reaction.
(b) Enzymes can change the direction of a reaction.
(c) Protein-ligand binding usually involves covalent bonds.
(d) The Kd is equal to the concentration of ligand when all of the binding sites are occupied.
(e) Hemoglobin exhibits cooperative binding of O2 while myoglobin does not.

Answer 1

a) Enzymes can change the rate of a reaction- True

enzymes decrease the activation energy of the reaction and increases the rate of the reaction.

b)  Enzymes can change the direction of a reaction-False.

enzymes do not change the direction of the reaction, the direction of the reaction depends on the concentration of the products.

c) Protein-ligand binding usually involves covalent bonds-False

the protein and the ligand can interact via hydrogen bonds, ionic bonds, Vander Waals interactions etc.

d) The Kd is equal to the concentration of ligand when all of the binding sites are occupied- False.

for the reaction ligand binding to the protein is

Kd=[P][L]/ [PL]

the Kd is the ratio of products of concentrations of protein and ligand to the concentration of protein-ligand complex.

the Kd is not equal to the concentration of ligand when all of the binding sites are occupied.

e) Hemoglobin exhibits cooperative binding of O2 while myoglobin does not-True.

hemoglobin has four subunits so the oxygen binding to the hemoglobin is co-operative that is binding of oxygen to one of the hemoglobin subunits facilitates the binding of oxygen to other subunits, but myoglobin has only one protein so it does not show co-operativity.