BIOCHEM EXAM 1 WILEY PLUS
QUESTIONS AND ANSWERS WITH
VERIFIED SOLUTIONS 100% CORRECT
(GRADED A+)
Hemoglobin's oxygen-binding curve is sigmoidal because - ANSWER✔✔ O2
binding shifts hemoglobin to a high-affinity conformation.
Respiring tissues release CO2, which leads to - ANSWER✔✔ a shift to the T state
of hemoglobin.
Collagen has an unusual amino acid composition because - ANSWER✔✔ only
certain residues can form a triple helix.
The motor protein myosin has - ANSWER✔✔ two heads attached to a rigid neck
lever.
In a motor protein, ATP is used to - ANSWER✔✔ alter the conformation of the
protein.
Protein X binds reversibly to ligand Y such that X + Y<--> XY, and the molar
concentrations of X, Y and XY are known. Which of the following represents the
dissociation constant (K) for this reaction? - ANSWER✔✔ K = [X][Y]/[XY]
Invariant residues are those that are essential for the structure and/or function of
the protein and cannot be replaced by other residues. Which amino acid residue in
the globin chain is most likely to be invariant? - ANSWER✔✔ His F8
, About two dozen histidine residues in hemoglobin are involved in binding the
protons produced by cellular metabolism. In this manner, hemoglobin contributes
to buffering in the blood, and the imidazole groups able to bind and release protons
contribute to the Bohr effect. One important contributor to the Bohr effect is His
146 on the β chain of hemoglobin, whose side chain is in close proximity to the
side chain of Asp 94 in the deoxy form of hemoglobin but not the oxy form. a.
What kind of interaction occurs between Asp 94 and His 146 in deoxyhemoglobin?
b. The proximity of Asp 94 alters the pK value of the imidazole ring of His. In
what way? - ANSWER✔✔ Under acidic conditions, His 146 will form an ion pair
with Asp 94, while the close proximity of Asp 94 increases the pKvalue of His
146.
Globular proteins are typically constructed from several layers of secondary
structure, with a hydrophobic core and a hydrophilic surface. Is this true for a
fibrous protein such as keratin? - ANSWER✔✔ Keratin has a mostly hydrophilic
core and exterior.
Which of the following statements about 2,3-bisphosphoglycerate (BPG) binding
is FALSE? - ANSWER✔✔ BPG aids oxygen delivery to tissues by increasing the
affinity of myoglobin for oxygen.
BPG does not affect the affinity of myoglobin for oxygen.
If a Lys residue that interacts with 2,3-bisphosphoglycerate (BPG) in the central
cavity of hemoglobin is changed to a Ser residue, how would this affect
hemoglobin behaviour? - ANSWER✔✔ The T state would be less stable.
The replacement of Lys with Ser would reduce the affinity of hemoglobin for BPG
and the T state would be less stable.
If curve 3 represents the binding of oxygen to Hb at pH 7.4, which curve represents
the binding of oxygen to Hb at pH 7.2? - ANSWER✔✔ A change from pH 7.4 to
pH 7.2 represents an increase in the concentration of H+ ions. As the concentration
QUESTIONS AND ANSWERS WITH
VERIFIED SOLUTIONS 100% CORRECT
(GRADED A+)
Hemoglobin's oxygen-binding curve is sigmoidal because - ANSWER✔✔ O2
binding shifts hemoglobin to a high-affinity conformation.
Respiring tissues release CO2, which leads to - ANSWER✔✔ a shift to the T state
of hemoglobin.
Collagen has an unusual amino acid composition because - ANSWER✔✔ only
certain residues can form a triple helix.
The motor protein myosin has - ANSWER✔✔ two heads attached to a rigid neck
lever.
In a motor protein, ATP is used to - ANSWER✔✔ alter the conformation of the
protein.
Protein X binds reversibly to ligand Y such that X + Y<--> XY, and the molar
concentrations of X, Y and XY are known. Which of the following represents the
dissociation constant (K) for this reaction? - ANSWER✔✔ K = [X][Y]/[XY]
Invariant residues are those that are essential for the structure and/or function of
the protein and cannot be replaced by other residues. Which amino acid residue in
the globin chain is most likely to be invariant? - ANSWER✔✔ His F8
, About two dozen histidine residues in hemoglobin are involved in binding the
protons produced by cellular metabolism. In this manner, hemoglobin contributes
to buffering in the blood, and the imidazole groups able to bind and release protons
contribute to the Bohr effect. One important contributor to the Bohr effect is His
146 on the β chain of hemoglobin, whose side chain is in close proximity to the
side chain of Asp 94 in the deoxy form of hemoglobin but not the oxy form. a.
What kind of interaction occurs between Asp 94 and His 146 in deoxyhemoglobin?
b. The proximity of Asp 94 alters the pK value of the imidazole ring of His. In
what way? - ANSWER✔✔ Under acidic conditions, His 146 will form an ion pair
with Asp 94, while the close proximity of Asp 94 increases the pKvalue of His
146.
Globular proteins are typically constructed from several layers of secondary
structure, with a hydrophobic core and a hydrophilic surface. Is this true for a
fibrous protein such as keratin? - ANSWER✔✔ Keratin has a mostly hydrophilic
core and exterior.
Which of the following statements about 2,3-bisphosphoglycerate (BPG) binding
is FALSE? - ANSWER✔✔ BPG aids oxygen delivery to tissues by increasing the
affinity of myoglobin for oxygen.
BPG does not affect the affinity of myoglobin for oxygen.
If a Lys residue that interacts with 2,3-bisphosphoglycerate (BPG) in the central
cavity of hemoglobin is changed to a Ser residue, how would this affect
hemoglobin behaviour? - ANSWER✔✔ The T state would be less stable.
The replacement of Lys with Ser would reduce the affinity of hemoglobin for BPG
and the T state would be less stable.
If curve 3 represents the binding of oxygen to Hb at pH 7.4, which curve represents
the binding of oxygen to Hb at pH 7.2? - ANSWER✔✔ A change from pH 7.4 to
pH 7.2 represents an increase in the concentration of H+ ions. As the concentration
