Carbon dioxide in venous blood
Carbon dioxide molecules are transpoed in the blood from body tissues to the lungs by one of three methods: dissolution directly into the blood, binding to hemoglobin, or carried as a bicarbonate ion. ... Second, carbon dioxide can bind to plasma proteins or can enter red blood cells and bind to hemoglobin Ref: guyton and hall textbook of medical physiology 12 edition page number: 359,360,361