where does carbon dioxide enter the blood
Oxygen diffuses from the blood/tissue fluid into cells where it is used in respiration to release energy. Carbon dioxide diffuses back into the blood from cells as it is a waste product made during respiration.Source(s): AS biology student. Elfsong Â· 7 years ago.or O2 it is denoted as pO2 and pCO2 for carbon dioxide. CO2 diffuses out through the venous blood into the lungs (via alveoli) due to concentration gradient. Similarly pO2 which is high in concentration in the alveoli coming from outside the blood capillaries diffuses into lungs.