chloride shift phenomenon

[SamarEsawy]

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surfing google books I found this

I marked my questions with red
1-first what makes the RBC membrane relatively impermeable to cations?
2-what makes the total number of ions inside the RBCs increase despite the fact that we exchange HCO3 for Cl ion

Thanks in advance

 

[Anastomoses]

First of all, your picture is so cute.

1. It's a semi-permeable membrane; I don't think the impermeability to cations is only particular to RBCs, I think most non-conducting cells are like that. It would probably have to do with the fact that their surface proteins don't have channels for the cations. That's my guess.
2. What I remember of the chloride shift is that it causes venous plasma chloride to be in less concentration than chloride in arterial plasma. Maybe someone else can help with the rest. 🙂

 

[SamarEsawy]

thank you Miss,Anastomosis
I wish I can understand my second question its really going over my head

 

[greatnt249]

thank you Miss,Anastomosis
I wish I can understand my second question its really going over my head

Yeah, seems to be a common theme. 🙄

 

[SamarEsawy]

2.) This would, I assume, be due to the fact that 1 mol of Cl- represents more ions than 1 mol of HCO3-, because Cl- has a lower weight than HCO3-. Not only this, but the antiporter moving Cl in and bicarbonate out may not move exactly 1:1 ratio, if that makes sense.

to achieve neutralization,the same number of ions must be exchanged right?
it's written in my text book also that during chloride shift phenomenon , the concentration of both cl- and HCo3 inside the RBCs are increasing I don't understand how the concentration of HCo3 is still increasing also it's being exchanged for CL-
thank you

 

[pathologyDO]

to achieve neutralization,the same number of ions must be exchanged right?
it's written in my text book also that during chloride shift phenomenon , the concentration of both cl- and HCo3 inside the RBCs are increasing I don't understand how the concentration of HCo3 is still increasing also it's being exchanged for CL-
thank you

I retracted that thought. It made sense to me until I looked up the antiporter (Band 3) and it indeed exchanges 1 chloride ion for every bicarbonate ion. So I cannot explain why there are more ions inside the cell. It also doesn't make sense that bicarb is increasing in the cell, when it is exiting the cell lol. confusing

 

[SamarEsawy]

I retracted that thought. It made sense to me until I looked up the antiporter (Band 3) and it indeed exchanges 1 chloride ion for every bicarbonate ion. So I cannot explain why there are more ions inside the cell. Maybe the wording is tricky, and they mean to say "there are more chloride ions inside the RBC than outside"

since we have more HCO3 inside the RBCs,HCO3 diffuses down its concentration gradient out of the RBC, and one Cl- ion replaces it,,so we still have the same number of osmotically active particles inside the RBCs so more water enters the RBCs I think of this explanation is this sounds logic to you?
but still can't explain how concentration of HCo3 is still increasing inside the RBCs

 

[Anastomoses]

to achieve neutralization,the same number of ions must be exchanged right?
it's written in my text book also that during chloride shift phenomenon , the concentration of both cl- and HCo3 inside the RBCs are increasing I don't understand how the concentration of HCo3 is still increasing also it's being exchanged for CL-
thank you

You'll have to quote the textbook word for word, but the reason your bicarbonate is increasing is that CO2 is still diffusing passively into the cells and being hydrated to become carbonic acid, which then loses the proton to become bicarbonate. I think you already understand that your Cl is increasing due to the exchange with bicarbonate.

 

[Anastomoses]

Also, Samar...you might find more people interested in these questions if you post them in the USMLE section. I think this area is more for chatty topics around medical school, curriculums, issues rather than actual book information.

 

[SamarEsawy]

Also, Samar...you might find more people interested in these questions if you post them in the USMLE section. I think this area is more for chatty topics around medical school, curriculums, issues rather than actual book information.

okay I'll try my luck there
thank you friend

 

[pathologyDO]

Good luck! Sorry I couldn't be of more help