Bich 409 Exam Two Test Questions
with Guaranteed Pass Solutions 2025-
2026 Updated.
small organisms' oxygen requirements are met by _________ ________ of oxygen through their
bodies - Answer passive diffusion
oxygen solubility in aqueous solution is _______ - Answer low
< 10^-4M
what is found in the blood of organisms that is able to carry oxygen concentrations of 0.01M
(same as the O2 concentration in the air of our atmosphere)? - Answer hemoglobin
an intracellular protein found in muscle tissue - Answer myoglobin
what is the function of myoglobin? - Answer to facilitate oxygen transport in rapidly respiring
muscle tissue
what limits the rate of oxygen delivery in the capillaries? - Answer the low solubility of
oxygen in aqueous solution
what increases the effective solubility of oxygen in muscle tissue? - Answer myoglobin
what is myoglobin composed of? - Answer a single polypeptide chain of 153 residues in 8
alpha-helices labeled A-H
how does myoglobin bind oxygen and what is another molecule that does this? - Answer it
binds it to a heme
hemoglobin
what does a heme consist of? - Answer a porphyrin consisting of 4 pyrrole rings linked by
methylene bridges
briefly describe the nitrogen in the heterocyclic, aromatic pyrrole ring - Answer the lone pair
of electrons of the nitrogen is required for aromaticity, it is not a basic nitrogen
what state is the central iron of protoporphyrin? - Answer FeII
,ferrous state
FeIII is considered? - Answer ferric
FeII is considered? - Answer ferrous
what happens if the iron is not oxidized into FeIII (ferric)? - Answer it forms metmyoglobin
(MetMB) or methemoglobin (MetHb)
do the met forms bind oxygen? - Answer no
the heme coordinates tightly to a water molecule as the sixth ligand
what enzyme in blood converts the FeIII iron cent back to the FeII? - Answer methemoglobin
reductase
what happens to the free heme in solution? - Answer it readily binds to oxygen, but the
oxygen quickly oxidizes it to the ferric state (FeIII)
what geometry do the iron atoms of heme bind to? - Answer they bind six ligands in an
octahedral geometry
what are the six ligands? - Answer four are the nitrogen atoms of the four pyrrole rings of
the heme
the fifth comes from histidine F8
when oxygen binds it becomes the sixth ligand
does the oxidation state of the iron change upon oxygen binding? - Answer no
how does oxygen bind in the deoxygenated state? - Answer it binds to the opposite face of
the heme from histidine so that the FeII center is octahedrally coordinate.
how does the electronic state of the heme change upon oxygenation? - Answer the
electronic state changes as indicated by the color change of blood upon binding oxygen, but the
iron remains in the ferrous state
the oxygenated heme of myoglobin - Answer oxymyoglobin
,what is the angle of the oxygen atom bound in the heme? - Answer it is not perpendicular to
the plane of the heme and has a 60 degree angle
the unoxygenated heme of myoglobin - Answer deoxymyoglobin
the sixth coordination site is vacant
how is the oxygen binding site a sterically hindered region? - Answer His-E7 is on the same
side of the heme plane that oxygen binds. it is too far away to coordinate with the iron of the
heme, but it can sterically interact with the binding of O2
what is the biological importance of the hindered oxygen binding site? - Answer - the free
heme in solution has 25,000 times more affinity for carbon monoxide than oxygen
- in Mb and Hb, CO only binds 250 times greater than O2 because His-E7 forces the CO molecule
to tilt away from the preferred perpendicular alignment with the plane of the heme
- this reduction allows trace amounts of CO to be generated during metabolism which otherwise
would occupy the Mb/Hb sites
describe the ferrous iron in deoxymyoglobin and what happens when oxygen binds - Answer
the ferrous iron has five ligands and lays 0.55 Angstroms above the plane of the heme towards
His-F8, giving the iron porphyrin a complex dome shape
in binding, the iron atom is pulled back into the plane of the heme such that it is only 0.26
Angstroms above the porphyrin
what is the name for the fraction of O2-binding sites occupied by O2? - Answer fractional
saturation (YO2)
YO2 equation for myoglobin (monomeric) - Answer YO2 = pO2 / (p50 + pO2)
partial pressure abbreviation - Answer pO2
what is the p50? - Answer the value of pO2 when YO2 = 0.50
the partial pressure when half of the myoglobin binding sites are occupied with oxygen
describe the oxygen saturation curve for myoglobin - Answer YO2 vs pO2; this occurs at a
pO2 of 1 torr or 1 mmHg
1-YO2 is the fraction of unbound sites
hyperbolic
, Hill Coefficient - Answer the slope of the hill plot at the point of log(Y/1-Y)=0, the midpoint of
binding
what is the Hill coefficient for myoglobin and what does it mean? - Answer 1
the oxygen atoms bind independently of each other
a compact globular protein that binds oxygen to a heme as a tetramer? - Answer
hemoglobin
what is the composition of hemoglobin? - Answer four polypeptide chains, each structurally
similar to the single polypeptide chain of myoglobin
each subunit contains a heme unit allowing hemoglobin to bind four oxygen atoms
adult hemoglobin is an....? - Answer alpha2beta2-type tetramer
describe the beta-subunit of hemoglobin? - Answer it is 7 amino acid residues shorter than
Mb 153 and its last helix H is shorter than Mb
describe the alpha-subunit of hemoglobin? - Answer it is 12 residues shorter and has a
shorter H helix and lacks Helix D
how is the tetrameric quaternary structure of hemoglobin important to its function? - Answer
when a molecule of O2 binds to a heme in Hb, the heme iron in drawn into the plane of the
porphyrin ring. this slight movement sets off a chain of conformational events that are
transmitted to the adjacent subunits, dramatically enhancing the affinity of the heme for oxygen
why do crystals of deoxyhemoglobin shatter when exposed to O2? - Answer the change in
structure that occurs upon oxygen binding
the Hb molecule is highly ________ and _________ - Answer symmetrical
spherical
where are the hemes in Hb located? - Answer the clefts between the E and F helices and are
exposed to the aqueous solvent
they are far apart
the closed two hemes are between alpha1 and beta2 or alpha2 and beta1 and are separated by
25 Angstroms
with Guaranteed Pass Solutions 2025-
2026 Updated.
small organisms' oxygen requirements are met by _________ ________ of oxygen through their
bodies - Answer passive diffusion
oxygen solubility in aqueous solution is _______ - Answer low
< 10^-4M
what is found in the blood of organisms that is able to carry oxygen concentrations of 0.01M
(same as the O2 concentration in the air of our atmosphere)? - Answer hemoglobin
an intracellular protein found in muscle tissue - Answer myoglobin
what is the function of myoglobin? - Answer to facilitate oxygen transport in rapidly respiring
muscle tissue
what limits the rate of oxygen delivery in the capillaries? - Answer the low solubility of
oxygen in aqueous solution
what increases the effective solubility of oxygen in muscle tissue? - Answer myoglobin
what is myoglobin composed of? - Answer a single polypeptide chain of 153 residues in 8
alpha-helices labeled A-H
how does myoglobin bind oxygen and what is another molecule that does this? - Answer it
binds it to a heme
hemoglobin
what does a heme consist of? - Answer a porphyrin consisting of 4 pyrrole rings linked by
methylene bridges
briefly describe the nitrogen in the heterocyclic, aromatic pyrrole ring - Answer the lone pair
of electrons of the nitrogen is required for aromaticity, it is not a basic nitrogen
what state is the central iron of protoporphyrin? - Answer FeII
,ferrous state
FeIII is considered? - Answer ferric
FeII is considered? - Answer ferrous
what happens if the iron is not oxidized into FeIII (ferric)? - Answer it forms metmyoglobin
(MetMB) or methemoglobin (MetHb)
do the met forms bind oxygen? - Answer no
the heme coordinates tightly to a water molecule as the sixth ligand
what enzyme in blood converts the FeIII iron cent back to the FeII? - Answer methemoglobin
reductase
what happens to the free heme in solution? - Answer it readily binds to oxygen, but the
oxygen quickly oxidizes it to the ferric state (FeIII)
what geometry do the iron atoms of heme bind to? - Answer they bind six ligands in an
octahedral geometry
what are the six ligands? - Answer four are the nitrogen atoms of the four pyrrole rings of
the heme
the fifth comes from histidine F8
when oxygen binds it becomes the sixth ligand
does the oxidation state of the iron change upon oxygen binding? - Answer no
how does oxygen bind in the deoxygenated state? - Answer it binds to the opposite face of
the heme from histidine so that the FeII center is octahedrally coordinate.
how does the electronic state of the heme change upon oxygenation? - Answer the
electronic state changes as indicated by the color change of blood upon binding oxygen, but the
iron remains in the ferrous state
the oxygenated heme of myoglobin - Answer oxymyoglobin
,what is the angle of the oxygen atom bound in the heme? - Answer it is not perpendicular to
the plane of the heme and has a 60 degree angle
the unoxygenated heme of myoglobin - Answer deoxymyoglobin
the sixth coordination site is vacant
how is the oxygen binding site a sterically hindered region? - Answer His-E7 is on the same
side of the heme plane that oxygen binds. it is too far away to coordinate with the iron of the
heme, but it can sterically interact with the binding of O2
what is the biological importance of the hindered oxygen binding site? - Answer - the free
heme in solution has 25,000 times more affinity for carbon monoxide than oxygen
- in Mb and Hb, CO only binds 250 times greater than O2 because His-E7 forces the CO molecule
to tilt away from the preferred perpendicular alignment with the plane of the heme
- this reduction allows trace amounts of CO to be generated during metabolism which otherwise
would occupy the Mb/Hb sites
describe the ferrous iron in deoxymyoglobin and what happens when oxygen binds - Answer
the ferrous iron has five ligands and lays 0.55 Angstroms above the plane of the heme towards
His-F8, giving the iron porphyrin a complex dome shape
in binding, the iron atom is pulled back into the plane of the heme such that it is only 0.26
Angstroms above the porphyrin
what is the name for the fraction of O2-binding sites occupied by O2? - Answer fractional
saturation (YO2)
YO2 equation for myoglobin (monomeric) - Answer YO2 = pO2 / (p50 + pO2)
partial pressure abbreviation - Answer pO2
what is the p50? - Answer the value of pO2 when YO2 = 0.50
the partial pressure when half of the myoglobin binding sites are occupied with oxygen
describe the oxygen saturation curve for myoglobin - Answer YO2 vs pO2; this occurs at a
pO2 of 1 torr or 1 mmHg
1-YO2 is the fraction of unbound sites
hyperbolic
, Hill Coefficient - Answer the slope of the hill plot at the point of log(Y/1-Y)=0, the midpoint of
binding
what is the Hill coefficient for myoglobin and what does it mean? - Answer 1
the oxygen atoms bind independently of each other
a compact globular protein that binds oxygen to a heme as a tetramer? - Answer
hemoglobin
what is the composition of hemoglobin? - Answer four polypeptide chains, each structurally
similar to the single polypeptide chain of myoglobin
each subunit contains a heme unit allowing hemoglobin to bind four oxygen atoms
adult hemoglobin is an....? - Answer alpha2beta2-type tetramer
describe the beta-subunit of hemoglobin? - Answer it is 7 amino acid residues shorter than
Mb 153 and its last helix H is shorter than Mb
describe the alpha-subunit of hemoglobin? - Answer it is 12 residues shorter and has a
shorter H helix and lacks Helix D
how is the tetrameric quaternary structure of hemoglobin important to its function? - Answer
when a molecule of O2 binds to a heme in Hb, the heme iron in drawn into the plane of the
porphyrin ring. this slight movement sets off a chain of conformational events that are
transmitted to the adjacent subunits, dramatically enhancing the affinity of the heme for oxygen
why do crystals of deoxyhemoglobin shatter when exposed to O2? - Answer the change in
structure that occurs upon oxygen binding
the Hb molecule is highly ________ and _________ - Answer symmetrical
spherical
where are the hemes in Hb located? - Answer the clefts between the E and F helices and are
exposed to the aqueous solvent
they are far apart
the closed two hemes are between alpha1 and beta2 or alpha2 and beta1 and are separated by
25 Angstroms
