QS Study

Bohr Effect

The shifting of Oxygen – Hemoglobin dissociation curve by the change of Carbon dioxide and H+ in the blood is called Bohr Effect. It refers to the observation that increases in the carbon dioxide partial pressure of blood or decreases in blood pH result in a lower affinity of hemoglobin for oxygen. It was first described in 1904 by the Danish physiologist Christian Bohr (father of famous physicist Niels Bohr).


Combination of Oxygen, with Hb in the lungs, causes the Hb to become stronger acid. Then, in turn, displaces Carbon dioxide (CO2) from blood in 2 ways.

(A) Highly acidic Hb less tendency to binds is the Carbon dioxide form carbamino Hb. So more Carbon dioxide is displacing from Hb and enters the lung alveoli.

(B) The more acidic Hb cause to release excess which binds with H+ which binds with HCO3 to form H2CO3. This acid breaks into CO2 and H2O and CO2 released from the blood into lung alveoli.

H+ + HCO3 → H2CO3 → H2O + CO2.

Occurs – In the pulmonary capillaries.

Physiological significance

  • Haldane effects approximately double the amount of CO2 released from the blood in the lung. When PO2 is high.
  • It also approximately doubles the amount of CO2 picked up by the blood in the tissue, when PO2 is low.
  • The Bohr Effect allows for improved acceptance of oxygen in metabolically active peripheral tissues such as exercising skeletal muscle. Increased skeletal muscle movement results in localized increases in the incomplete pressure of carbon dioxide which in turn reduces the local blood pH.