Hemoglobin (Hb) in the blood absorbs oxygen to form oxyhemoglobin [Hb(O2)2], which transports oxygen to the cells. The equilibrium can be generally represented by the following

(though it is actually composed of a series of equilibria in which Hb binds from between 1 and 4 O2 molecules per unit depending on the partial pressure of O2.) The cells consume oxygen, producing water and CO2 as a result of cellular respiration. While de-oxyhemoglobin has alower affinity for CO2 than for O2 it transports CO2 from the tissues back to the lungs. In addition, Hb has a much higher affinity for CO than for O2.

Hb + 2O2(gas) <==> Hb(O2)2

Normal blood pH is about 7.4. Under metabolic stress a situation known as acidosis can result in which the pH of the blood drops. This results in a shift of the above equilibrium to the left. Give an explanation for each of the following observations based upon the principles of equilibrium.

(a) Free hemoglobin readily picks up O2 in the lungs

(B) Oxyhemoglobin releases O2 to the tissues

(C.) A person is hyperventilating, his/her dissolved CO2 levels rise in the blood, what effect will this have on O2 transport to the tissues? Why?

(a) Free hemoglobin readily picks up O2 in the lungs:

This observation can be explained based on the principles of equilibrium and the fact that hemoglobin has a higher affinity for O2 compared to CO2 or CO. In the lungs, where the oxygen concentration is higher, the equilibrium of the reaction shifts to the right:

Hb + 2O2(gas) <==> Hb(O2)2

This means that hemoglobin readily binds with O2, forming oxyhemoglobin. The higher concentration of oxygen in the lungs favors the formation of Hb(O2)2, allowing hemoglobin to efficiently pick up oxygen molecules from the inhaled air.

(b) Oxyhemoglobin releases O2 to the tissues:

In the tissues, where the concentration of O2 is lower due to its utilization during cellular respiration, the equilibrium of the reaction shifts to the left:

Hb + 2O2(gas) <==> Hb(O2)2

This means that oxyhemoglobin, which has bound oxygen molecules, will release some of them to the surrounding tissues. The lower concentration of oxygen in the tissues favors the dissociation of Hb(O2)2, allowing oxygen to be released for cellular use.

(c) A person is hyperventilating, his/her dissolved CO2 levels rise in the blood, what effect will this have on O2 transport to the tissues? Why?

Hyperventilation leads to a decrease in blood CO2 levels, not an increase. However, let's consider the effect of increased dissolved CO2 levels in the blood:

When the dissolved CO2 levels rise, it leads to a decrease in blood pH, causing acidosis. This decrease in pH causes a shift in the equilibrium equation for oxygen binding to hemoglobin:

Hb + 2O2(gas) <==> Hb(O2)2

The shift in equilibrium favors the dissociation of Hb(O2)2, resulting in the release of oxygen from hemoglobin. This means that when CO2 levels rise and acidosis occurs, more oxygen is released from oxyhemoglobin, enhancing oxygen transport to the tissues. The decrease in pH weakens the binding affinity between hemoglobin and oxygen, promoting oxygen release for cellular use.