Question

9.

A.  V_max is a poor metric for indicating enzyme efficiency because:

1) It changes as a result of using competitive inhibitor

2) The total enzyme concentration affects the value of V_max

3) It requires measuring enzyme velocity

4) It is independent of the total enzyme concentration

5) It varies as a function of the K_M value of the substrate

B. What is the main disadvantage of using k_cat to compare the efficiencies of enzymes? What is the main advantage of using k_cat/K_M instead of k_cat?

1) k_cat applies at low concentrations of substrate; k_cat/K_M applies at cellular concentrations of substrate

2)        k_cat is difficult to measure; k_cat/K_M is simpler to measure

3) k_cat requires you to know the total enzyme concentration; k_cat/K_M does not require you to know the total enzyme concentration

4) k_cat applies only at substrate concentrations that can be achieved in a laboratory setting; k_cat/K_M applies at cellular concentrations of substrate

5) k_cat requires you to know the V_max of the reaction under saturation conditions; k_cat/K_M does not require you to know V_max

C. If the P₅₀ of a globin protein is 48 mmHg, then 25% of O₂ binding sites would be occupied when pO₂ is  ________ mmHg.

1) 12 mmHg                                                                                                                                                    4) 96 mmHg

2) 18 mmHg                                                                                                                                                    5) None of the above

3) 24 mmHg

D. Which one of the following statements about protein-ligand binding is correct?

A) The K_a (association constant) is equal to the concentration of ligand when all of the binding sites are occupied.

1) The K_a is equal to the concentration of ligand when 50% of the binding sites are occupied.

2) The larger the K_a, the weaker the binding affinity

3) The larger the K_a, the smaller the K_d (dissociation constant)

4) The K_d is a concentration of ligand when q < 0.5

E.  In the binding of oxygen to myoglobin, the relationship between the partial pressure of oxygen and the fraction of binding sites occupied by oxygen can best be described as

1) linear with a negative slope                                                                                  4) hyperbolic

2) linear with a positive slope                                                                                  5) More than one of the above

3) sigmoidal

Answer 1