Question

How will an increase of blood $C{O_2}$ affect hemoglobin’s affinity for ${O_2}\,?$

Answer 1

An adult human contains about $5\,L$of blood each $mL$ of which contains $5000\,million$ blood cells, each cell having $2.5 \times {10^5}$ hemoglobin molecules. Red blood cells have a relatively short life span of $100 - 120\,days$ and hence about one percent of hemoglobin molecules are replaced daily. Hemoglobin is important for dioxygen transport.

Complete step-by-step answer: Hemoglobin is actually a tetramer of myoglobin consisting of four myoglobin like units linked together by salt bridge interactions.
Hemoglobin present in red blood cells of arteries binds to four ${O_2}$ by allosteric effect to form$Hb{\left( {{O_2}} \right)_4}$. The hemoglobin molecules transport ${O_2}$ through the arteries which finally reaches the capillaries. In active muscles ${O_2}$ is converted to $C{O_2}$ hence capillaries have excess amounts of $C{O_2}$ present in them. The pH of capillary blood is low as $C{O_2}$ reacts with water to form carbonic acid which ultimately releases a proton under the action of carbonic anhydrase.
$C{O_2} + {H_2}O \to {H_2}C{O_3}\xrightarrow{{carbonic\,\,anhydrase}}{H^ + } + HC{O_3}^ -$.
At low pH removal of ${O_2}$ from hemoglobin is favoured and it is converted to myoglobin.
Conversely, if there is a decrease in $C{O_2}$, it provokes an increase in pH, which results in a hemoglobin molecule in picking up more ${O_2}$. This is known as the Bohr Effect.

Additional Information: To serve as an ideal carrier of ${O_2}$, oxyhemoglobin must be able to release the dioxygen to the cell to which ${O_2}$ is to be delivered. This is achieved by the globin proteins surrounding the heme unit.

Note: Hemoglobin is an important bio-inorganic molecule without which our $C{O_2} - {O_2}$ balance cannot be maintained properly. In order to achieve this, scientists have now discovered a complex known as Vaskas’s complex which does the same work as ${O_2}$ and is called a synthetic oxygen carrier.