Factors Triggering Sickling in HbS - USMLE Forums
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Old 11-14-2013
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RBC Factors Triggering Sickling in HbS

PT with SCD, which of the following will aggregate sickeling

A) B chain folding
B) interaction with HbF
C) Proton Release

D) Oxygen unloading >>> this the right answer, but I don't got it unloading o2 that mean the Hb has the o2 how come this will aggregate HbS

E) 2,3 bisphosphoglycerate depletion when there low 2,3DPG with increase affinity to o2 and will prevent sickling . but also o2 unloading will prevent siclking bcz mean high affinity

So i dont know why the correct A is o2 unloading . ????
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Old 11-14-2013
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Flip to the FA topic about sickle cell anemia....it says right there, how sickling occurs; deoxygenated HbS polymerizes. So deoxygenation or dehydration (loss of that O2 part of water) will cause sickling. U world has a big technical explanation about it as well.

Hb is attracted to 2,3 BPG...hence, if you have 2,3 BPG you get more affinity to O2, and hence less sickling.
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It's oxygen unloading.
When 2,3 bpg increases it decreases the affinity for oxygen hence right shifts the curve and more oxygen unloading and more sickling
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....Thank you
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Old 11-14-2013
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Quote:
Originally Posted by usmletaker2013 View Post
It's oxygen unloading.
When 2,3 bpg increases it decreases the affinity for oxygen hence right shifts the curve and more oxygen unloading and more sickling
thats right . I know they have also asked this question somewhere in the NBMEs...
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