hemoglobin structure and function Flashcards
A heme prosthetic group consists of iron bound to a ________ ring.
protoporphyrin.
Each red blood cell in the body contains approximately _______ molecules of hgb.
280 million
When 0 zero O2 molecules are bound to hemoglobin, it is said to be in what configuration
T or taut
The T configuration is caused by lack of O2 binding which alters ______ within hemoglobin
inter- and intra- salt bonds within the molecule.
Define P50
the partial pressure of oxygen at which the O2 carrying protein in 50% saturated.
Hemoglobin in a tetramer whereas myglobin is a ______
monomer.
the basic shape of the hemoglobin O2 dissociation curve follows what values for % saturation at the following partial pressures?:
10-
30-
40-
60-
10-10
30-60
60-90
40-75
What can shift the O2 dissociation curve to the left?
decreased BPG/DPG
decreased acidity (increased pH)
decreased temp.
What can shift the O2 dissociation curve to the right?
increased BPG/DPG
increased acidity (decreased pH)
increased temp.
How will a rightward shift affect O2 affinity?
decrease affinity
How will a leftward shift affect O2 affinity?
increase affinity
Describe the Bohr effect
CO2 produced by tissues in metabolism is converted to bicarb and H+ by carbonic anhydrase. This leads to a drop in pH (increase in acidity) which shifts the O2 curve to the right, decreasing O2 affinity and allowing the tissues to more readily receive O2. technically any shift due to pH is known as the Bohr effect.
How can we rationalize the O2 curve shift as a result of change in temperature?
With exercise or fever (increase in temp) metabolism is higher and the need for O2 greater. Thus, an increase in temp. will shift the curve to the right and decrease O2 affinity for hgb, allowing O2 to be unloaded into the tissues more readily.
How is BPG created in the body?
It is a byproduct of anaerobic metabolism. Thus, increasing amounts of BPG suggest the need for more O2. BPG decreases O2 affinity for hgb and allows O2 to be more readily picked up by the tissues.
Alpha-like genes (for hgb) are on what chromosome? what about Beta-like genes?
alpha- chromosome 11
Beta- chromosome 16
What are the 3 distinct hemoglobins present in embryos (week 4-14 only)?
Hemoglobin Gower I- (zeta2 epsilon2)
Hemoglobin Gower II- (alpha2 epsilon2)
Hemoglobin Portland- (zeta2 gamma2)
Just remember:
zeta alpha zeta
Compared to adult hgb, Fetal hgb has a _____ oxygen affinity.
higher. This make sense because oxygen needs to be able to transfer from maternal circulation to fetal circulation through the placenta.
What cause Fetal hgb to have a higher affinity for O2 than adult hgb?
Fetal hgb binds BPG poorly. This stabilizes hemoglobin in the R state and causes the curve to shift to the left. The Bohr effect is also increase by 20% in fetal hgb. This causes H+ ions to go into maternal circulation as they pass through the placenta. Thus, pH rises in Baby circulation and affinity increases.
In normal adults Hgb F makes up what % of blood?
What is a Heinz body?
precipitated, denatured hemoglobin
High affinity hemoglobins can lead to:
erythrocytosis (too many RBCs).
Low affinity Hemoglobins can lead to:
cyanosis
erythropoietin is released from the_____
kidney
Hemoglobin Zurich is a mutation which causes what to happen?
increased binding to Carbon Monoxide
Hemoglobin Koln is a mutation which causes what to happen?
unstable Hemoglobin
Heme needs what kind of iron to form itself?
ferrous (2+)
The ferric (3+) form of iron leads to what kind of hemoglobin?
methemoglobin. If cannot reduce ferric to ferrous form, leades to methemoglobinemia
How is iron maintained in the ferrous form within an RBC?
NADPH methemoglobin reductase pathway
What is the most common hereditary cause of methemoglobin?
deficiency of cytochrome b5 reductase
with high amounts of methemoglobin, hemoglobin has a _____ ability to carry O2. Also the curve shifts____.
decreased.
left. This further decreases O2 ability to reach the tissues
With 8-12% methemoglobin a person becomes
cyanotic but asymptomatic otherwise.
Carbon Monoxide poisoning is detected by____?
co-oximetry (not pulse oximetry which cannot differentiate between carboxyhemoglobin and oxyhemoglobin).
What is the difference between co-oximetry and pulse oximetry?
Co- measures at 4 wavelengths and can discern between carboxyhemoglobin, oxyhemoglobin and methemoglobin while pulse oximetry absorbs at only 2 wavelengths and cannot differentiate between these two. The both work using light emitting diodes and receptors that measure whats in your blood essentially.
