Pc02 is in alveolar air and in tissues
a) 158 mmhg, 100 mmhg
b) 100 mmhg, 40 mmhg
c) 760 mmhg, 158 mmhg
d) 40 mmhg, 45 mmhg
e) 40 mmhg, 100 mmhg

The answer to fill in the blanks in the question: PCO2 is: in alveolar air and in tissues, would be, D: 40mmHg for alveolar air and 45mmHg, for the blood that is returning from the tissues.

Explanation:

The reason for this comes from the purpose and the places that respiration takes place. Respiration has two purposes: take in oxygen from the air, and release CO2, a waste of cellular respiration processes, produced by the cells in tissues. The reason for the differences in molecules of CO2 being higher in the blood that comes from tissues, and not in the air from the alveoli is that in the alveoli, oxygen dissolves into the tissue of the alveoli and passes to the blood that is prepared to capture as many of the molecules as possible, to carry them to the cells. But in tissue blood, since oxygen has already been used in respiration, there is a high production of CO2. These molecules will dissolve in the blood and will be carried to the lungs, but this time to be released out of the body.