When we breathe in air, our body needs a way to transport oxygen efficiently to the tissues. Oxygen dissolved directly into the blood is inadequate to supply our body with enough oxygen. Our red blood cells contain a protein, hemoglobin, which increases the capacity of blood to carry O₂ by about 70-fold.

Red blood cells contain enormous numbers of hemoglobin molecules. Hemoglobin consists of four polypeptide subunits, each of which surrounds a heme group—an iron-containing ring structure that can reversibly bind a molecule of O₂. Thus, each hemoglobin molecule can bind and release up to four O₂ molecules, enabling the blood to carry a large amount of O₂ to the body’s tissues.

In this tutorial, investigate several factors that influence hemoglobin's ability to pick up and release oxygen. Some of these factors facilitate efficient oxygen exchange, while others result in death of the organism.

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