All of the cells in the body need oxygen. Hemoglobin molecules in red blood cells transport oxygen through the bloodstream. Oxygen is loaded onto hemoglobin molecules in the lungs and unloaded from the hemoglobin molecules in the tissues.
What drives the unloading of oxygen from hemoglobin molecules in the tissues?

A. the low partial pressure of oxygen in the tissues
B. the high partial pressure of carbon dioxide in the tissues
C. the low partial pressure of carbon dioxide in the tissues
D. the high partial pressure of oxygen in the tissues

Option B) the high partial pressure of carbon dioxide in the tissues.

Explanation:

The high concentration of oxygen in the alveoli of the lungs unloads H+ and carbon dioxide (CO2) from the hemoglobin, just as the high concentration of H+ and CO2 in active tissues unloads Oxygen from hemoglobin molecules.

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.