Hemoglobin is a
red blood cell protein that transports oxygen via its four heme-bound subunits from the lungs to the tissues
Gives blood its red color
if abnormal in primary structure can lead to diseases or mutations such as sickle cell
bind of oxygen is not cooperative
binds oxygen in muscle cells
displays cooperatively in oxygen binding and release
is a quaternary structure
can lead to sickle cell disease if abnormalities exist in primary structure
The ability of myoglobin and hemoglobin to bind oxygen depends on the presence of a heme group
The heme group consist of
inorganic component called protoporphyrin and a central iron ion in the ferrous form, the only form that can bind oxygen
organic component called protoporphyrin and a central iron ion in the ferrous form, the only form that can bind oxygen
inorganic component called protoporphyrin and a central iron ion in the ferrous form, one out of many forms that can bind oxygen
organic component called protoporphyrin and a central iron ion in the ferrous form, one out of many forms that can bind oxygen
The iron lies in the middle of the protoporphyrin bound to three nitrogens
Iron can from two additional bonds, at the fifth
fourth( fifth, second, fourth ) and sixth
fifth( sixth, third, fifth ) coordination sites
The imidazole ring of a histidine called the proximal histidine is occupied by the
The coordination site binds
The structure of myoglobin prevents the release of reactive oxygen species
Superoxide is very reactive, and should it leave the heme, ferric iron (Fe3+) would result.
Heme with Fe3+
does not bind oxygen
does bind oxygen
Myoglobin with iron in the Fe3+ state is called
The distal histidine of myoglobin prevents the release of
A hydrogen bond donated by the distal histidine residue to the bound oxygen molecule helps stabilize oxymyoglobin
Myoglobin consist of
a single polypeptide chain, formed of α- helices connected by turns, with one oxygen binding site
a multiple polypeptide chains, formed of α- helices connected by turns, with one oxygen binding site
a multiple polypeptide chains, formed of β- helices connected by turns, with one oxygen binding site
a single polypeptide chain, formed of β- helices connected by turns, with one oxygen binding site
Hemoglobin consist of
2 identical α chains
4 identical α chains
2 identical β chains.
4 identical β chains.
Many of the helices in each subunit are arranged in a pattern also found in myoglobin, a structure called the fold
Hemoglobin binds oxygen cooperatively
Hemoglobin( Myoglobin, Hemoglobin ) displays a hyperbolic
sigmoid( hyperbolic, sigmoid ) oxygen binding curve, while hemoglobin
myoglobin( hemoglobin, myoglobin ) exhibits a sigmoid
hyperbolic( sigmoid, hyperbolic ) curve, indication that O2 binding and release is cooperative
non-cooperative( cooperative, non-cooperative )
Hemoglobin is not effective in providing oxygen to exercising tissue
Because of cooperatively between O2 binding sites,
hemoglobin delivers more O2 to actively metabolizing tissues than would myoglobin or any noncooperative protein, even one with optimal O2 affinity
hemoglobin delivers more O2 to actively metabolizing tissues than would myoglobin or any cooperative protein, even one with optimal O2 affinity
myoglobin delivers more O2 to actively metabolizing tissues than would hemoglobin or any noncooperative protein, even one with optimal O2 affinity
The quaternary structure of deoxyhemoglobin is referred to as the T state
R state( T state, R state ), while that of oxyhemoglobin is the R state
T state( R state, T state ).
binding of oxygen
facilitates the release of oxygen
R state has a greater affinity for oxygen than does the T state
It is sequential in that in hemoglobin with one O2 bound,
the remaining subunits are in the T state.
the remaining subunits are in the R state.
It is concerted in that in hemoglobin with three O2 bound,
the remaining subunit is in the R state
the remaining subunit is in the T state
The transition from deoxyhemoglobin (T state) to oxyhemoglobin (R state) occurs upon oxygen binding.
2,3 Bisphosphoglycerate in red cells is crucial in determining the oxygen affinity of myoglobin
2, 3-Bisphosphoglycerate (2,3-BPG) stabilizes the T state
R state( T state, R state ) of hemoglobin and thus facilitates the release
binding( release, binding ) of oxygen.
2. 2, 3-BPG binds to a pocket in the hemoglobin tetramer that exists only when hemoglobin is in the R state.
In fetal hemoglobin,
the β chain is replaced with a γ chain
The fetal α2γ2 hemoglobin does not bind 2, 3-BPG as well as adult hemoglobin does.
The reduced affinity for 2, 3-BPG results in fetal hemoglobin having a higher affinity for oxygen, binding oxygen when the mother’s hemoglobin is releasing oxygen
Carbon monoxide binds so tightly to iron of hemoglobin that it stabilizes the R state (binding of oxygen) to such a degree that the R to T transition does not occur.
The stimulation of oxygen release (R state) by carbon dioxide and Hydrogen ions
The stimulation of oxygen release (T state) by carbon dioxide and Hydrogen ions
Most carbon dioxide is carried to the lungs in the blood as bicarbonate ion.
Carbonic acid dissociates to form HCO3- and H+ resulting in a rise in pH inside the cell
Sickle cell anemia results from the aggregation of mutated deoxyhemoglobin molecules
is a genetic disease caused by a mutation resulting in the substitution of valine for glutamate at position 6 of the β chains.
can be fatal when both alleles of the β chain are mutated.
trait offers some protection from malaria
one allele is mutated and one is normal such individuals are asymptomatic.
caused by an imbalanced production of hemoglobin chains
another common genetic disorder of hemoglobin
another common genetic disorder of myoglobin
caused by the absence or underproduction of one of the hemoglobin chains
caused by the presence or overproduction of one of the hemoglobin chains