The normal pH of blood is 7.40+ 0.05 and is controlled in part by the H2COs/HCO

Question

The normal pH of blood is 7.40+ 0.05 and is controlled in part by the H2COs/HCO system. The pKa for carbonic acid is 6.1 under physiological conditions. buffer a. Assuming that the K, value for carbonic acid at 25°C applies to blood, what is the [H2CO3]/ [HCO3] ratio in normal blood?(3 pts) In acidosis, a condition that can have many causes, the blood is too acidic. What is the [H2COs]/ [HCOs ] ration in a patient whose blood pH is 7.20(severe acidosis)? Compare this to the ratio in part a. Does this make sense? Explain (3 pts) b.

Explanation / Answer

pH = 7.40+0.05= 7.45 pH=7.40-0.05=7.35 pka= 6.1

1. when pka= 6.1

we know from Henderson equation,

pH = pka + log10 {IA-I/IHAI)

Here A- = HCO3- and HA= H2CO3

Putting the value pH= 7.45

7.45= 6.1+ log 10 (I HCO3- I/ I H2CO3 I )

1.35= log 10 ( I HCO3- I/ IH2CO3I)

IH2CO3I/IHCO3-I= 0.044

Now putting the pH= 7.35

similarly using the above formula we will get,

I H2CO3 I/ I HCO3- I = 0.056

2. Now for acedolysis pH =7.20

pka = 6.1

using Henderson equation,

pH= pka + log10 ( I HCO3- I/ I H2CO3 I)

7.20=6.1 + log 10 ( I HCO3- I/I H2CO3 I)

I H2CO3 I/I HCO3- I = 0.079

the ratio of the conc of H2CO3 and HCO3- is increased in the second case. here H2CO3 and HCO3- acts as buffer.. when acedolysis takes place then conc of H + increases in the solution and in order to resist the increased H+ more of H2CO3 will produce according to le chatelier principle. ( act of buffer solution ) . Hence the ratio is increased.

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