Step I Nbme 6

[DrTacoElf]

Did you guys notice a question about CO2 transport in the blood is miskeyed I think. I put most C02 is carried as HCO3- in the RBC (carbonic anhydrase reaction) and it marked me as having it wrong?

http://en.wikipedia.org/wiki/Carbon_dioxide

 

[MilkmanAl]

HCO3 isn't carried in the RBC. It's in solution. 😉 It gets exchanged for Cl- after carbonic anhydrase does its thing.

That said, I think I recall hearing that a few of the NBME questions are, in fact, miskeyed. I can't remember where, so take it with some salt.

 

[DrTacoElf]

Yeah i think you are right just didn't think detailed enough 😛

 

[Bassix]

Milkman is correct.

With that, I'm assuming one of the answers was carbaminohgb, which I believe is the correct answer.

 

[DrTacoElf]

CO2 is carried in blood in three different ways. (The exact percentages vary depending whether it is arterial or venous blood).
Most of it (about 70% – 80%) is converted to bicarbonate ions HCO3
by the enzyme carbonic anhydrase in the red blood cells,[52] by the reaction CO2 + H2O → H2CO3 → H+ + HCO3

5% – 10% is dissolved in the plasma[52]
5% – 10% is bound to hemoglobin as carbamino compounds[52]

It should just be HCO3 in serum mostly not carbamino.

 

[Bassix]

ahh I see. Miscomm. I read it as IN the RBC.
"C02 is carried as HCO3- in the RBC"