Tutorial Answer 1

Hemoglobin is an oxygen transport molecule that is able to pick up oxygen in the lungs, where the oxygen concentration is high, and carry it through the circulatory system and release it to the tissues, where the oxygen concentration (tension) is low. Its special feature is the reversibility by which it binds oxygen under one set of conditions, and releases it under another. Without this reversibility hemoglobin would be of no use as a carrier molecule. In vertebrate systems hemoglobin also functions to pick up about 25% of the carbon dioxide produced in the tissues, and transport it (in a loose binding known as carbondioxide hemoglobin) to the lungs where it is exhaled to the outside. The rest of the carbon dioxide is transported to the lungs dissolved in the water portion of the blood.