Structure and Function of Hb Flashcards
What shape does a hemoglobin molecule have
Tetrametric shape
What are the 4 types of hemoglobin
Adult Hb (HbA)
Fetal Hb (HbF)
HbA2
HbA1C
Which hemoglobin has 2 α and 2 β-chains
Adult Hb and HbA1C
Which hemoglobin has 2α and 2γ chains
Fetal Hb
Which hemoglobin has 2α and 2δ chains
Adult HbA2
What is another name for HbA1C
Glycated Hb
genes for beta chains are found on which chromosome
chromosome 11
genes for alpha chains are found on which chromosome
chromosome 16
which fetal site of globin synthesis is 12 weeks till birth
spleen
beta globins are missing from hemoglobin due to low transcription. which part of the gene is probably defected
locus control region
what type of porphyrin ring does Hb contain
protoporphyrin IX
Which form of iron contained in heme allows it to bind to oxygen
ferrous oxide (Fe2+)
A large amount of ferric oxide in Hb can indicate which pathological condition
Methemoglobinemia
What is the clinical presentation for a deficiency of NADH-metHb and what is the condition called
Cyanosis
Methemoglobinemia
drugs containing which suppose can lead to acquired methemoglobinemia
Nitrates
ferrous oxide is held in the center of the porphyrin rings of heme by which molecules
nirtogen
which globin chain has more alpha helical segments (alpha or beta)
beta
the proximal histidine around heme binds to _____ while the distal histidine stabilizes ____
Fe2+
O2
Which form of Hb is more abundant in the tissues? Why is this?
T-form because it has less affinity for O2 so O2 can be off loaded easier to tissues that need it
Which form of Hb is more abundant in the lungs? Why is this?
R-form because it has a higher affinity for O2 and in the lungs the RBCs there need to hold on to the O2 they just received from the alveolar air
myoglobin is mainly found in which tissues
Heart and skeletal muscles
Pertaining to the structure of myoglobin why does it make sense that it’s dissociation curve is hyperbolic
it is monomeric, with only one heme group so it just accepts O2 until it;s saturated
Pertaining to the structure of myoglobin why does it make sense that it’s dissociation curve is sigmoidal
it is tetrameric, so the one O2 binds which increases the affinity for more O2 so the slope of the curve increases as the consecutive sites get filled until they are all filled
in which type of hemoglobin does the alpha globin chain have 8 alpha helical segments
myoglobin
Which four factors can influence loading and unloading of O2 in Hb
pH
partial pressure CO2
partial pressure of O2
2,3-bisphosphoglycerate
a defect in the second half of glycolysis could potentially affect oxygen dissociation in Hb why?
in glycolysis, 1,3-bisphosphoglycerate is made which is used to make 2,3-bisphosphoglycerate which aids in oxygen dissociation
What factors affecting O2 dissociation would cause the a right shift in the O2 dissociation curve
What does a right shift indicate
decreased CO2
high pH
high 2,3-bisphosphoglycerate
A right shift indicates more release of O2
What factors affecting O2 dissociation would cause the a left shift in the O2 dissociation curve
What does a left shift indicate
increased CO2
low pH
low 2,3-bisphosphoglycerate
A left shift indicates less release of O2
A right shifted O2 dissociation curve more resembles which form of Hb
Why is this?
T-form
Because in the T-form, Hb has less affinity for O2 so there is more release of O2
A left shifted O2 dissociation curve more resembles which form of Hb
Why is this?
R-form
Because in the R-form, Hb has more affinity for O2 so there is less release of O2
Elevated 2,3-bisphosphoglycerate is seen in which conditions
Hypoxia (high altitude) and chronic anemia
Does 2,3-bisphosphoglycerate bind to alpha or beta chains
beta chain
Absence of what in HbF make them bind poorly to 2,3-bisphosphoglycerate
beta globin chain
Why does HbF need to have high affinity for O2
to trap maternal O2 for the fetus
What are the 4 main hemoglobinopathies
sickle cell anemia (HbS)
hemoglobin C
hemoglobin SC
thalassemia
What is the defect in sickle cell anemia (HbS)
change of glutamic acid to valine in the 6th postion of the beta chain
What is the defect in HbC
change of glutamic acid to lysine in the 6th postion of the beta chain
Thalassemia is due to what
decreased Hb
Methylene blue can be used to treat a condition with a deficiency in which enzyme?
What is the condition?
Deficiency in NADH-metHb reductase
Methemoglobinemia
Carboxy hemoglobin causes Hb to be predominantly in which form? this leads to?
R-type
Less O2 dissociation (hypoxia)
