Allosteric Effects(Biochemistry ) Questions and answers for exam Preparation

Question 1. The conformational changes from the T to the R state is initiated by

reorganization of protein-protein contacts between the individual subunits
movement of the F-helix, which contains the proximal His
binding of oxygen to the heme
movement of the proximal histidine towards the heme

Explanation:-

Answer: Option C. -> binding of oxygen to the heme

Question 2. Bisphosphoglycerate (BPG) cannot bind to the oxygenated R state of hemoglobin because

it is displaced from the heme by oxygen
its binding pocket becomes too small to accommodate BPG
it is displaced from the heme by movement of the proximal histidine
BPG binds to the R state with the same affinity as the T state

Explanation:-

Answer: Option B. -> its binding pocket becomes too small to accommodate BPG

Question 3. An allosteric activator

both (a) and (c)
decreases the binding affinity
stabilizes the R state of the protein
increases the binding affinity

Explanation:-

Answer: Option A. -> both (a) and (c)

Question 4. When protein binds two ligands in a non-cooperative manner, then the x-intercept of the Scatchard Plot is

2
1
not defined
None of these

Explanation:-

Answer: Option A. -> 2

Question 5. The Hill coefficient (nH) for myoglobin and hemoglobin are respectively

1.2 and 4.5
1.0 and 2.8
2.8 and 1.0
4.5 and 1.2

Explanation:-

Answer: Option B. -> 1.0 and 2.8

Question 6. Small molecules affect hemoglobin (Hb) by

decreasing Hb affinity for O2
increasing [H+]
increasing Hb affinity for O2
increasing [H+] and decreasing Hb affinity for O2

Explanation:-

Answer: Option D. -> increasing [H+] and decreasing Hb affinity for O2

Question 7. In hemoglobin, allosteric effects occur

for maintaining Fe in the Fe2+ state
to minimize oxygen delivery to the tissues
only in humans
to maximize oxygen delivery to the tissues

Explanation:-

Answer: Option D. -> to maximize oxygen delivery to the tissues

Question 8. A protein that shows infinite cooperative for binding of n ligands will

only be found in either the unliganded form or the fully liganded form
show a Hill coefficient (nH) of 0.0
both (b) and (c)
show a Hill coefficient (nH) of n

Explanation:-

Answer: Option C. -> both (b) and (c)

Question 9. A protein that binds two ligands in a non-cooperative manner will show

a hyperbolic binding curve
a sigmodial binding curve
both (b) and (c)
a linear Scatchard Plot

Explanation:-

Answer: Option C. -> both (b) and (c)

Question 10. O2 binding to hemoglobin results in

100-fold lower affinity for the last O2 bound than for the first
both (a) and (b)
extensive protein conformational change
100-fold higher affinity for the last O2 bound than for the first

Explanation:-

Answer: Option B. -> both (a) and (b)