Increased oxygen transport to tissues: CO2 and H+ alter oxygen-haemoglobin dissociation (bohr effect)

2021-05-16 11:25 PM

When blood passes through tissues, CO2 diffuses from tissue cells into the blood, this diffusion increases blood PCO2, thereby increasing blood H2CO3 (carbonic acid) and H+ ion concentration. This effect will shift the oxygen-haemoglobin dissociation graph to the right and down.

 

Shifting to the right of the Oxy-haemoglobin dissociation graph in response to an increase in blood CO2 and H+ ions has a significant effect on enhancing O2 release from the blood into tissues and enhancing oxygen binding to haemoglobin. in the lungs. This is called the Bohr effect, which can be explained as follows: When blood passes through tissues, CO2 diffuses from the tissue cells into the blood, this diffusion increases blood PCO2, thereby increasing blood H2CO3 (acidity) carbon dioxide) and the concentration of H+ ions. This effect will shift the oxygen-haemoglobin dissociation graph to the right and down, as shown in the figure, forcing O2 out of the haemoglobin and thereby increasing the amount of O2 transported to the tissues.

Figure 41-10. The shift of the oxy-haemoglobin dissociation curve to the right is due to an increase in hydrogen ion concentration (decrease in pH). BPG, 2,3-biphosphoglycerate.

The exact opposite effects occur in the lungs, where CO2 diffuses from the blood into the alveoli. This diffusion reduces the PCO2 in the blood and reduces the concentration of H+ ions, which will shift the graph of oxygen-haemoglobin dissociation to the left and up. As a result, the amount of O2 bound to haemoglobin at any given oxygen pressure in the alveoli is significantly increased, thus allowing large amounts of O2 to be transported to the tissues.