Oxygen–hemoglobin dissociation curve

Oxygen–hemoglobin dissociation curve

The oxygen–hemoglobin dissociation curve.

The oxygen–hemoglobin dissociation curve is a graphical representation of the relationship between the partial pressure of oxygen (pO2) and the oxygen saturation (SO2) of hemoglobin in the blood. This curve is crucial for understanding how oxygen is transported in the blood and how it is released to tissues.

Shape of the Curve

The curve is typically sigmoidal (S-shaped) due to the cooperative binding of oxygen to hemoglobin. As one molecule of oxygen binds to hemoglobin, it increases the affinity of the remaining sites for oxygen, facilitating further binding. This is known as cooperativity.

Factors Affecting the Curve

Several factors can shift the oxygen–hemoglobin dissociation curve:

• pH and Bohr effect: A decrease in pH (acidosis) shifts the curve to the right, while an increase in pH (alkalosis) shifts it to the left.
• Carbon dioxide levels: Increased levels of carbon dioxide shift the curve to the right.
• Temperature: Higher temperatures shift the curve to the right.
• 2,3-Bisphosphoglycerate (2,3-BPG): Increased levels of 2,3-BPG shift the curve to the right.

Physiological Significance

The position of the curve is vital for understanding how oxygen is loaded in the lungs and unloaded in the tissues. A rightward shift facilitates oxygen unloading in tissues, while a leftward shift enhances oxygen loading in the lungs.

Fetal Hemoglobin

Comparison of fetal and adult hemoglobin.

Fetal hemoglobin (HbF) has a higher affinity for oxygen than adult hemoglobin (HbA), resulting in a leftward shift of the dissociation curve. This allows the fetus to effectively extract oxygen from the maternal blood supply.

Related Pages

• Hemoglobin
• Bohr effect
• 2,3-Bisphosphoglycerate
• Fetal hemoglobin
• Partial pressure