Hemoglobin and Myoglobin
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Myogoblin and hemogoblin contain ____ in the center
Where is Mb located?
What is the function of Mb
carry oxygen from the blood to mitochondria
Adult Hb contains 2 __ chains and 2 ___ chains
List 4 functions of Hb
transport oxygen, carbon dioxide, hydrogen and nitric oxide
How many oxygen can Hb transport at once?
What is p50?
The pO2 at which 1/2 the available binding sites are occupied
How does a decrease in the pH effect the oxygen binding curve?
There is a right shift. oxygen is more readily released
How does an increase in carbon dioxide concentration effect the oxygen binding curve?
it acidifies the blood and there is a right shift
List two other things that cause a right shift in the curve?
increase in 2,3 BPG and increase in temperature
What does a right shift accomplish?
moves the p50 to the right. this allows oxygen to be dropped off earlier in the circulation
How does fetal Hb differ from an adult
There are gamma side chains instead of beta. this is significant because 2,3-bpg works through the beta sub unit, thus fetal Hb is unnaffected by 2,3-bpg
Why was sickle cell mutation hard to diagnose prenatally?
the Beta side chains of Hb were not present pre birth to diagnose sickle sell mutation
What enzyme facilitates ferric Hb(Fe+3) to ferrous Hb (Fe +2)
What are the vasoregulatory properties of NO?
vasodilation, inhibition of smooth muscle cell, proliferation and migration and anti platelet effects
How does 2,3-BPG effect O2 concentrations?
- hb-2-3-bpg increase O2 content.
- 2,3-BPG binds to a deoxyhemogoblin taking up O2's spot
In which human organ is Mb most important?
Mb is most important in the heart.
Explain the cause and importance of a right shift in the Hb/O2 binding curve
- A right shift in the Hb/O2 binding curve is caused by either: 1) a lowering of pH,
- 2) an increase in [CO2],
- 3) an increase in temperature or
- 4) an increase in [2,3-BPG]. The right shift lowers Hb/Mb affinity for oxygen. Therefore, at lower pressures Hb is more likely to release its O2, such as in the muscles.
In Hb, how does the binding of the first oxygen molecule affect the binding of the next ones?
Hb exhibits the cooperative effect. After binding its 1st O2 molecule, additional O2 molecules bind with increased affinity.
What is the Bohr effect?
The Bohr Effect is the increase of acidity of Hb as it binds O2.
What is the physiological importance of cooperativity in Hb function?
Once one O2 molecule binds to Hb, it has a higher affinity for other O2 molecules. Hb has less affinity for O2 at lower pressures than Mb. This allows O2 to be released to tissues, where Mb can then pick it up. Also, once one O2 is dropped off, it is "easier" for other O2 molecules to be dropped off.
Compare the behavior of Mb and Hb with respect to O2, CO2 and H+.
A right shift in the Hb/O2 binding curve is caused by a lowering of pH, increase in [CO2], increase in temperature or increase in [2,3-BPG]. The right shift is significant because it lowers Hb/Mb affinity for oxygen. The result is that at lower pressures, Hb is more likely to release its O2, such as at the cellular level.
How does the protein (globin) portion of Mb or Hb affect the reactivity of heme?
The proteins have a "blocking effect" that weakens the attraction of Heme-O2 interaction and prevents intense interaction of Oxy-Heme groups with each other. (Heme-oxy alone will bind too well, rending heme unable to pick up other O2)
How and where does 2,3-BPG interact with Hb? Where does 2,3-BPG come from?
2-3 BPG comes from they glycolytic pathway. It binds to the deoxy form of Hb, between the β-chains, making it more resistant to oxygenation (The same effect as a "right shift.")
How does fetal Hb (HbF) differ from HbA?
Fetal Hb has γ-chains instead of β-chains. Therefore it is not affected by 2,3-BPG. The net effect is a "left shift" of the Hb-O2 curve.
What does the Hill equation describe?
Express oxygen binding with respect to oxygen pressure and P50. and to ask what difference does copoerativity have on the oxygen binding curve.
The Hill equation describes the relationship of log (% sat) to log (P). This can be used to calculate a value n, which is a measure of a molecules cooperativity.
n is normally the measure of cooperativity, and 1 ≤ n ≤ # of sidechains (although 0 ≤ n ≤ 1 could indicate negative cooperativity)
How does NO (nitric oxide) interact with Hb, and what is the physiological significance of that interaction?
NO can reversibly bind to heme and to cysteine residues in the globin. Hb can also catalyze NO2- to NO (under hypoxic conditions). This makes Hb a potentially important mediator of vascular tone and helps protect the mitochondria against free radical damage from ETC cycle.
What is the p50 of myogoblin and hemogoblin?
- myogoblin p50 is 3-5 torr
- hemogoblin p50 is 26 torr
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