BICH 409 EXAM II QUESTIONS WITH VERIFIED
ANSWERS
Which of the following statements concerning the binding of oxygen and hemoglobin is
correct?
a. Hemoglobin tetramer binds 4 molecules of BPG.
b. The oxygen affinity of hemoglobin increases as the percent saturation increases.
c. The Bohr effect results in a lower affinity for oxygen at higher pH values.
d. Carbon dioxide increases the oxygen affinity of hemoglobin by carbamylating the
amino terminal ends of the 4 polypeptide chains.
e. Oxyhemoglobin and deoxyhemoglobin have the same affinity for (H+). - Answers - b.
The oxygen affinity of hemoglobin increases as the percent saturation increases.
When a glutamic acid residue is shifted from the surface of a protein into a hydrophobic,
nonpolar pocket in the interior of the protein, the pKa of the glutamic acid ________
a. remains unchanged
b. increases
c. decreases - Answers - b. increases
Protoporphyrin consists of:
a. 4 imidazole rings linked by methylene bridges.
b. 4 pyridine rings linked by methylene bridges.
c. 4 benzene rings linked by methylene bridges.
d. 4 pyrrole rings linked by methylene bridges.
e. 4 indole rings linked by methylene bridges. - Answers - d. 4 pyrrole rings linked by
methylene bridges.
2,3-bisophosphoglycerate:
a. increases the oxygen binding affinity of myoglobin.
b. binds to hemoglobin and stabilizes the R-state.
c. binds to the distal histidine of hemoglobin.
d. is bound to hemoglobin primarily through electrostatic interactions.
e. increases the oxygen binding affinity of hemoglobin. - Answers - d. is bound to
hemoglobin primarily through electrostatic interactions.
In both hemoglobin and myoglobin, the role of the proximal histidine is to:
a. Participate in oxygen binding by forming a hydrogen bond with O2.
b. Participate in the binding 2,3 Bisphosphoglycerate.
c. Protect iron atom from being oxidized into the ferric state.
d. Bind a proton that contributes to the Bohr effect.
e. Coordinate to the heme iron. - Answers - e. Coordinate to the heme iron.
If the pH decreases from 7.4 to 7.3, the p50 of hemoglobin would:
, a. cannot be determines
b. remain unchanged
c. none of these
d. increase
e. decrease - Answers - d. increase
Which of the following statements about the oxidation state of iron is true?
a. The iron center of the heme in the Methemoglobin is in the Fe2+ state.
b. A water molecule binds to the heme bound iron when the iron is in the ferrous state.
c. The binding of oxygen in hemoglobin or myoglobin, oxidizes the heme iron from the
Fe2+ state to the Fe3+ state.
d. None of these statements are true.
e. Oxygen binds to the heme bound iron when the iron is in the ferric state . - Answers -
d. None of these statements are true.
A monomeric oxygen-binding protein has a fractional saturation of 0.8 when pO2 = 8
torr. What is the value of p50 for this protein and what is the value of the hill coefficient
n? - Answers - p50 = 2
n=1
Hemoglobin carries CO2 from the tissues back to the lungs by:
a. Converting CO2 to bicarbonate
b. Binding CO2 in the central cavity of hemoglobin
c. None of these
d. Coordinating the CO2 to the iron of the hemes
e. Carbamylation of N-terminals of the 4 polypeptide chains - Answers - e.
Carbamylation of N-terminals of the 4 polypeptide chains
In both hemoglobin and myoglobin, the role of the proximal histidine is to:
a. Coordinate to the heme iron.
b. Participate in oxygen binding by forming a hydrogen bond with O2.
c. Participate in the binding 2,3, Bisphosphoglycerate.
d. Protect iron atom from being oxidized into the ferric state.
e. Bind a proton that contributes to the Bohr effect, - Answers - a. Coordinate to the
heme iron.
As oxygen binds to the Hb subunits:
a. His F8 pulls the iron atom out of the plane out of the plane of the heme to trigger the
T --> R transformation.
b. His F8 dissociates from heme iron coordination to trigger T --> R transformation.
c. The oxygen displaces His E7 releasing the E helix to trigger T --> R transformation.
d. The iron atom moves into plane of the heme to trigger the T --> R transformation.
e. Each heme rotates 15 degrees triggering the T --> R transformation. - Answers - d.
The iron atom moves into plane of the heme to trigger the T --> R transformation.
ANSWERS
Which of the following statements concerning the binding of oxygen and hemoglobin is
correct?
a. Hemoglobin tetramer binds 4 molecules of BPG.
b. The oxygen affinity of hemoglobin increases as the percent saturation increases.
c. The Bohr effect results in a lower affinity for oxygen at higher pH values.
d. Carbon dioxide increases the oxygen affinity of hemoglobin by carbamylating the
amino terminal ends of the 4 polypeptide chains.
e. Oxyhemoglobin and deoxyhemoglobin have the same affinity for (H+). - Answers - b.
The oxygen affinity of hemoglobin increases as the percent saturation increases.
When a glutamic acid residue is shifted from the surface of a protein into a hydrophobic,
nonpolar pocket in the interior of the protein, the pKa of the glutamic acid ________
a. remains unchanged
b. increases
c. decreases - Answers - b. increases
Protoporphyrin consists of:
a. 4 imidazole rings linked by methylene bridges.
b. 4 pyridine rings linked by methylene bridges.
c. 4 benzene rings linked by methylene bridges.
d. 4 pyrrole rings linked by methylene bridges.
e. 4 indole rings linked by methylene bridges. - Answers - d. 4 pyrrole rings linked by
methylene bridges.
2,3-bisophosphoglycerate:
a. increases the oxygen binding affinity of myoglobin.
b. binds to hemoglobin and stabilizes the R-state.
c. binds to the distal histidine of hemoglobin.
d. is bound to hemoglobin primarily through electrostatic interactions.
e. increases the oxygen binding affinity of hemoglobin. - Answers - d. is bound to
hemoglobin primarily through electrostatic interactions.
In both hemoglobin and myoglobin, the role of the proximal histidine is to:
a. Participate in oxygen binding by forming a hydrogen bond with O2.
b. Participate in the binding 2,3 Bisphosphoglycerate.
c. Protect iron atom from being oxidized into the ferric state.
d. Bind a proton that contributes to the Bohr effect.
e. Coordinate to the heme iron. - Answers - e. Coordinate to the heme iron.
If the pH decreases from 7.4 to 7.3, the p50 of hemoglobin would:
, a. cannot be determines
b. remain unchanged
c. none of these
d. increase
e. decrease - Answers - d. increase
Which of the following statements about the oxidation state of iron is true?
a. The iron center of the heme in the Methemoglobin is in the Fe2+ state.
b. A water molecule binds to the heme bound iron when the iron is in the ferrous state.
c. The binding of oxygen in hemoglobin or myoglobin, oxidizes the heme iron from the
Fe2+ state to the Fe3+ state.
d. None of these statements are true.
e. Oxygen binds to the heme bound iron when the iron is in the ferric state . - Answers -
d. None of these statements are true.
A monomeric oxygen-binding protein has a fractional saturation of 0.8 when pO2 = 8
torr. What is the value of p50 for this protein and what is the value of the hill coefficient
n? - Answers - p50 = 2
n=1
Hemoglobin carries CO2 from the tissues back to the lungs by:
a. Converting CO2 to bicarbonate
b. Binding CO2 in the central cavity of hemoglobin
c. None of these
d. Coordinating the CO2 to the iron of the hemes
e. Carbamylation of N-terminals of the 4 polypeptide chains - Answers - e.
Carbamylation of N-terminals of the 4 polypeptide chains
In both hemoglobin and myoglobin, the role of the proximal histidine is to:
a. Coordinate to the heme iron.
b. Participate in oxygen binding by forming a hydrogen bond with O2.
c. Participate in the binding 2,3, Bisphosphoglycerate.
d. Protect iron atom from being oxidized into the ferric state.
e. Bind a proton that contributes to the Bohr effect, - Answers - a. Coordinate to the
heme iron.
As oxygen binds to the Hb subunits:
a. His F8 pulls the iron atom out of the plane out of the plane of the heme to trigger the
T --> R transformation.
b. His F8 dissociates from heme iron coordination to trigger T --> R transformation.
c. The oxygen displaces His E7 releasing the E helix to trigger T --> R transformation.
d. The iron atom moves into plane of the heme to trigger the T --> R transformation.
e. Each heme rotates 15 degrees triggering the T --> R transformation. - Answers - d.
The iron atom moves into plane of the heme to trigger the T --> R transformation.
