Question

Physiological buffer is the system that controls output of acids , bases or CO2 ( carbon dioxide). true or false?

Answer 1

TRUE

Explaination - Physiological buffers are chemicals used by the body to prevent large changes in the pH of a bodily fluid. The four physiological buffers are the bicarbonate, phosphate, hemoglobin, and protein systems.

The pH of a buffer is determined by the Henderson-Hasselbalch equation:

pH=pKa+log(A−HA)

The buffer is best able to resist changes in pH when the pH of the buffer is close to the pH of blood (7.37 to 7.42), so the pKa of the acid should be close to 7.4.

Carbonate Buffer

The equilibrium is

H2CO3(aq)+H2O(l)⇌HCO−3(aq)+H3O+(aq); pKa=6.1

This buffer functions in exactly the same way as the phosphate buffer, but it is not ideal because its pKa is too far from pH 7.4.

Perhaps more importantly, the enzyme carbonic anhydrase converts H2CO3 into CO2 that is dissolved in the blood and is then exhaled as CO2gas.

Phosphate Buffer

The phosphate buffer system consists of H2PO−4 and HPO2−4 ions.

The equilibrium is

H2PO−4(aq)+H2O⇌H3O+(aq)+HPO2−4(aq); pKa=7.21

The phosphate buffer can easily maintain a pH of 7.4.

Hemoglobin

The general equation is:

HHb++O2+H2O⇌HbO2+H3O+; pKa=6.8

It shows that oxygenation of Hb promotes the formation of H3O+.

This shifts the bicarbonate buffer equilibrium towards CO2 formation, and CO2 is released from the red blood cells.

Proteins

A protein is a long chain of amino acid residues, but this long chain still has free carboxylate groups COO− and free amino groups NH2.

We could write the equation for a protein buffer system as

H3+N—R—COO−+H2O⇌H2N—R—COO−+H3O+

The protein can then act as a buffer.