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21 Cards in this Set
- Front
- Back
how many O2 molecules does myoglobin carry
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1
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how many O2 does hemoglobin transport
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4
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can Hb carry O2 when the iron is in the Fe3+ form?
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no
then Hb is called 'methemoglobin' |
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whats the basis for cooperative binding of O2 in Hb
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O2 binds, drags the proximal histidine, causing conformational change
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what do you call Hb bound to CO
what color is it |
Carboxyhemoglobin
cherry red |
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why is carboxyhemoglobin toxic?
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it prevents already-bound O2 from dissociating
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why does CO bind to Hb much less strongly than to free Hb
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it only binds to the iron in a strained configuration d/t a distal histidine group, O2 binds at an angle so its not affected
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does the Tense or Relaxed form have HIGHER affinity for O2 binding
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Relaaaaxed
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what does BPG stand for
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2,3 - Biphosphoglycerate
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whats BPG do?
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Negative allosteric effector of O2 binding to Hb
decreases affinity of Hb for O2 |
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BPG is synthesized from a precursor in the glycolytic pathway. What are 2 implications of this
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1. deficiency in hexokinase decreases BPG in a cell, so Hb will bind O2 more tightly
2. deficiency in pyruvate kinase (the last enzyme in the path) means an accumulation of all intermediates, including 1-3 BPG, the precursor of BPG, curve shifts to right, weaker binding of O2 |
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does Mb or Hb bind O2 more tightly
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Mb (curve is to the left)
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Does BPG promote O2 dumping at peripheral tissues?
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yes
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whats HbF
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fetal hemoglobin
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does HbF bind O2 more or less tightly than HbA (the hemoglobin found in RBCs)
and why? |
more tightly
This promotes the transfer of O2 from maternal HbA to fetal HbF across the placenta |
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what happens to blood that is stored for transfusion?
what does this mean clinically? what is the clinical solution? |
it loses the BPG from RBCs
for 24-48 hours Hb holds O2 much too tightly BPG is charged and cannot cross the RBC membrane. The nucleoside Inosine is added to the blood which is uncharged, gets into RBCs and enters the PPP and is eventually converted to BPG |
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why do H+ ions decrease Hb affinity for O2
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they protonate the histidine residues, salt linkages are formed that stabilize the deoxy form of Hb
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whats that Hemoglobin that binds glucose and is important for assessing diabetic patients?
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Hb A(1c) the Ic should be subscript
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how many peptide chains in Mb
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1
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חיה
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be alive, live
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whats the mechanism of sickle cell anemia
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A point mutation causes coding of valine instead of glutamate in position 6 of the Hb beta chain. The resulting abnormal Hb exhibits changes in solubility and molecular stability. These properties are responsible for the profound clinical expressions of the sickling syndromes.
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