Write 4 to 6 sentences to describe what happens in the lungs, where the partial pressure of oxygen gas is high. Then, describe what happens when the blood travels to the tissue, where oxygen levels are low. Be sure to include the equilibrium constant expressions in your analysis.
In the lungs, where the partial pressure of oxygen gas is high, oxygen diffuses from the alveoli into the bloodstream. This occurs due to a concentration gradient, in which the high partial pressure of oxygen in the alveoli drives the movement of oxygen into the blood. This process is facilitated by the binding of oxygen to hemoglobin molecules in red blood cells, forming oxyhemoglobin. The equilibrium constant expression for the binding of oxygen to hemoglobin is K = [HbO2] / ([Hb][O2]), where [HbO2] represents the concentration of oxyhemoglobin, [Hb] represents the concentration of deoxyhemoglobin, and [O2] represents the concentration of dissolved oxygen.
When the blood travels to the tissues, where oxygen levels are low, the opposite process takes place. Due to the lower partial pressure of oxygen in the tissues, the equilibrium shifts towards the dissociation of oxyhemoglobin, releasing oxygen into the surrounding tissues. This is guided by the equilibrium constant expression for the dissociation of oxyhemoglobin, which is expressed as K = ([Hb][O2]) / [HbO2]. Under these conditions, the deoxygenated blood returns to the lungs to pick up more oxygen, perpetuating the cycle of oxygen transport and exchange in the body.