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9 Cards in this Set

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  • Back
Hemoglobin structure
-4 ploypeptides ea. has its own heme:
adult hemeoglobin=alpha 2,beta 2
(HbA)
minor adult hemo=alpha 2 sigma 2 (HbA2)
fetal=alpha 2, gamma2 (HbF)
-subunits interact by salt bonds and h bonds
-histadine that also binds w/ Fe
-Fe on heme can only bind O2 in the ferrous state Fe2
-apoprotein protects heme from oxidation
-distal histidine dec Hgb affinity for CO
Methemoglobin
-nonfunxnal oxidized form of Hgb
-useless as an O2 xporter
-can't bind O2 b/c is in the ferric state Fe3
How methemoglobin happens
-poisoning w/ oxidizing agents i.e. chlorox
-overprod of oxidants by enzymes
-failure of a cell to make intracellular reductants
-congenital replacement of the proximal histidine of Hb by tyrosine
-failure of the enzyme methemoglobin reductase
can be tx w/ reducing agent like methylene blue
Carbon monoxide
-competitive agonist
-binds to heme instead of O2
-binds irreversibly to Hgb (cyanosis)cherry red
-tx w/ hyperbaric O2
Allosteric properties
alternative conformations:
R(relaxed)=oxyheme
T (tense)=deoxyhem
O2 binding breaks salt bonds b/t subunits and rearranges h bonds changing the structure from T to R
Positive cooperativty
R has a inc affinity for O2 so there's a + cooperativity b/t 2 O2 binding sites:binding of O2 to 1 heme inc the affinity of the 3 other hemes
-shows a sigmoidal curve @ p50 oxygen carrier is 1/2 sat w/ o2 @ torr of 26
-o2 is a ligand for heme
-myoglobin has a hyperbolic curve and it's torr at 1/2 sat is 1
Negative cooperativity
2,3 bisphosphoglycerate:
binds to beta chains in T form which lowers the o2 affinity
Bohr effect
-dec PH dec o2 binding affinity of hgb this shifts curve to right, stimulates o2 delivery
-co2 causes o2 to be released in active tissues i.e. muscles
Fetal hgb
has an inc o2 affinity for o2 than HbA b/c BPG is less tightly bound than in adults allows o2 to go from mom to baby