Partial pressure of oxygen in alveoli:

Ans. (b) 103 mmHgRef: Harrison 18th edition, Chapter 252Partial Pressures of blood gases* Atmosphere: pO2=160mmHg, pCO2=0.3mmHg* Alveolar air: pO2=l05mmHg, pCO2=40mmHg* Oxygenated blood: pO2=100mmHg, pCO2=40mmHg* Tissues: pO2=40mmHg, pCO2=45mmHg* Deoxygenated blood: pO2=40mmHg, pCO2=45mmHgMust KnowO2 and CO2 in blood* 1.5% O2 dissolved in blood* 98.5% O2 carried by hemoglobin (Hb-O2)# Hb can carry up to four molecules of O, (four = saturation)# PO2 determines Hb saturation# Also pH, temperature and Pco2 affects Hb-O2 binding