Britannica Sources used in this answer

What is the Bohr effect in oxygen transport by blood?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Blood plasma — blood Blood sediment in test tubes, showing plasma (clear fluid), red blood cells (red), and the release of hemoglobin into the surrounding plasma (pink).

The Bohr effect describes the physiological phenomenon where the oxygen affinity of hemoglobin decreases in response to a lower pH (increased acidity) in the blood.12

This effect is primarily driven by the concentration of carbon dioxide in the tissues. As metabolic activity produces carbon dioxide, it diffuses into the blood and reacts with water to form carbonic acid, which dissociates into bicarbonate and hydrogen ions. The resulting increase in hydrogen ion concentration lowers the blood pH.123

The Bohr effect functions as a critical regulatory mechanism for oxygen delivery:

In the tissues: The lower pH and higher carbon dioxide levels cause hemoglobin to change its molecular shape, reducing its affinity for oxygen and facilitating the release of oxygen to cells that need it for energy.24
In the lungs: The environment is more alkaline (higher pH), which causes hemoglobin to bind more tightly to oxygen, promoting efficient uptake.2

This process ensures that oxygen is effectively transported from the lungs to metabolically active tissues throughout the body.24