Hemoglobin transports the majority of oxygen in the arterial blood to the tissue. In an adult, the A1hemoglobin molecule can reversibly bind with four oxygen molecules. Oxygen must be released from hemoglobin in the tissues. Dissociation of oxygen from hemoglobin occurs in a characteristic fashion: the sigmoid, or S-shaped, curve. A normal curve is shown in the image on the right in blue when the blood pH is in the normal range (7.35-7.45).
The curve will shift to the left (shown in green in the image) when hemoglobin has an increased affinity for oxygen, resulting in less oxygen released to the tissue.
The curve will shift to the right (shown in red in the image) when hemoglobin has a decreased affinity for oxygen, resulting in more oxygen released to the tissue.
Certain conditions in the body will cause a right or left shift in the oxygen dissociation curve. Shifts are the body's response to a problem.
