Question

$C{O}_2$ dissociates from carbaminohemoglobin when

• A. $pC{O}_2$ and $p{O}_2$ are equal
• B. $p{O}_2$ is high and $pC{O}_2$ is low
• C. None of the above
• D. $pC{O}_2$ is high and $p{O}_2$ is low

Answer 1

The correct option is B $p{O}_2$ is high and $pC{O}_2$ is low

$pC{O}_2$ is high and $p{O}_2$ is low :

High $pC{O}_2$ and low $p{O}_2$ in tissues favour the formation of carbaminohemoglobin. Hence, the dissociation of $C{O}_2$ from carbaminohemoglobin will not occur.

$p{O}_2$ is high and $pC{O}_2$ is low :

$O_2$ is the dominant gas in alveoli [partial pressure of $O_2$ is high in alveoli] compared to $C{O}_2$. Also, the concentration of hydrogen ions is low there which favors the oxygenated state of hemoglobin ($R$-state). As a result, $C{O}_2$ is dissociated from $Hb$ and oxyhaemoglobin is formed. In this way, $C{O}_2$ is exhaled out of the alveoli when the carbaminohemoglobin carried by the $RBC$ reaches the lungs.

$pC{O}_2$ and $p{O}_2$ are equal :

When the partial pressure of both the gases, $pC{O}_2$ and $p{O}_2$ are equal, they will remain in equilibrium. Hence, no dissociation of carbon dioxide from carbaminohemoglobin will take place.

Final answer : b. $p{O}_2$ is high and $pC{O}_2$ is low