24._____
Which property is shared by both myoglobin and hemoglobin?
a)
Both are saturated with oxygen at low oxygen concentrations.
b)
Both display cooperative binding when transporting oxygen.
c)
Both contain strands of
β
-pleated sheet with a zig-zag shape.
d)
Both contain segments of
α
-helix with a spiral shape.
25._____
Which occurs when a hemoglobin molecule binds oxygen?
a)
Oxygen molecules in the lungs bind irreversibly to the protein’s heme
groups.
b)
The second oxygen molecule binds more easily than the first oxygen
molecule.
c)
The
α
subunits bind oxygen while the
β
subunits control cooperativity.
d)
Ionic bonds form between subunits which changes the quaternary structure.
26._____
Which change occurs when a hemoglobin subunit binds oxygen?
a)
A histidine residue changes position within the subunit.
b)
An iron atom is removed from a porphyrin group.
c)
The oxygen binds to amino acids within a segment of
α
-helix.
d) The oxygen causes a covalent crosslink to form within the subunit.
27._____
Which occurs when a hemoglobin molecule binds oxygen in the lungs?
a)
Each iron-porphyrin group can reversibly bind four oxygen molecules.
b)
Salt bridges between subunits break as the first oxygen binds.
c)
The first oxygen molecule binds more easily than the last oxygen molecule.
d)
Cooperative binding of oxygen causes the four subunits to dissociate.
28. _____ When myoglobin is denatured using heat
a) its amino acid composition will change.
b) its amino acid sequence will change.
c) its tertiary structure will change.
d) its C-terminal will change.
29._____
When hemoglobin is treated with urea and
β
-mercaptoethanol
a) its molecular weight will be unchanged.
b) its quaternary structure will be unchanged.
c) its primary structure will be unchanged.
d) its conformation will be unchanged.
30._____ Protein Z functions as an oxygen transport protein, and shares 60% of its primary
structure with myoglobin while the other 40% is different. Which is likely to be a
characteristic of Protein Z?
a) It probably contains one heme group that can bond two oxygen molecules.
b) It probably contains both
α
subunits and
β
subunits.
c) It probably could function even if a mutation changes one of the amino
acids in part of the primary structure that is shared with myoglobin.
d) It probably could function even if a mutation changes one of the amino
acids in part of the primary structure that is different from myoglobin.
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