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Old 09-05-2011
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Help Confused about buffering for CO2 transport

In BRS Physiology it states :


H+ is buffered inside the RBCs by deoxyhemoglobin. Because deoxyhemoglobin is a better buffer for H+ than is oxyhemoglobin, it is advantageous that hemo globin has been deoxygenated by the time blood reaches the venous end of the capillaries (Le., the site where CO2 is being added).

now we know the equation is :

CO2 + H20 --> H2CO3 ---> H+ + HCO3-

( H+ goes to Hb, and HCO3- goes out, CL- comes in)

So how is buffering H+ ions helping more CO2 to enter the cell, because technically if I buffer the H+ I go back the equation above :/... Or is it buffering with Hb???

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Old 09-06-2011
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Quote:
Originally Posted by USMLE2011m View Post
In BRS Physiology it states :


H+ is buffered inside the RBCs by deoxyhemoglobin. Because deoxyhemoglobin is a better buffer for H+ than is oxyhemoglobin, it is advantageous that hemo globin has been deoxygenated by the time blood reaches the venous end of the capillaries (Le., the site where CO2 is being added).

now we know the equation is :

CO2 + H20 --> H2CO3 ---> H+ + HCO3-

( H+ goes to Hb, and HCO3- goes out, CL- comes in)

So how is buffering H+ ions helping more CO2 to enter the cell, because technically if I buffer the H+ I go back the equation above :/... Or is it buffering with Hb???

so what i know is, CO2 is leaving the cell in the form of HCO3, so leaving H+ inside, so whenever there is gradient new CO2 will automatically come in because the old one has already left the cell in the form on HCO3. and also this CO2 is coming from the tissues! so tissues make more and more C02 and it enters due to gradient. High to low!
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Old 09-07-2011
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There is the enzyme carbonic anhydrase involved.
Though I am not sure how it works and where it comes from.
Kaplan notes talk about carbonic anhydrase and its action on CO2 and H20,
but I am not sure though.
I am confused about it.

I would like to know does carbonic anhydrase cause chloride shift from erythrocytes and lets the CO2 be capturet within the cell?
Is it the same carbonic anhydrase that works in the renal tubules and in the pancres?
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Old 09-25-2013
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Default Chloride shift

think about Hb like someone poor that got greedy with money(Oxygen): when it was poor (in the tissue) was giving Oxigen away, now (in the lungs) it's overloaded with Oxigen and wants to keep it in.

Remember these 2 rules:
1) Chloride follows Oxigen
2) H+ follows CO2

If you apply the rules to lungs and tissues therefore:
  • in the LUNGS Hb gets O2 and gives CO2. Chloride follows the O2 and goes IN the cells (RBCs). H+ follows the CO2 (or HCO3-) and goes out.
  • in the TISSUES(venous blood) Hb gets CO2 and gives O2. H+ follows the CO2 in the RBCs, Chloride follows O2 in the tissues/venous blood.
I know it seems silly, but it helped me.
Please, correct me if you find anything wrong
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