Question

Explain why the Bohr effect is good news for active muscles during exercise. How does this mechanism allow for effective gas exchange?

Answer 1

The Bohr effect describes hemoglobin’s lower affinity for oxygen secondary to increases in the partial pressure of carbon dioxide and decreases in blood pH. This lower affinity, in turn, enhances the unloading of oxygen into tissues to meet the oxygen demand of the tissue.

With exercise the heomoglobin curve shifts to right. When the curve shifts to the right in the Bohr's effect the blood is releasing more oxygen for Aerobic exercise. The Bohr effect refers to the loss of affinity for O2 with decreasing pH (increased acidity), as occurs in the microcirculation as oxygen is consumed and CO2 (carbonic acid) is released by tissues. The Bohr effect means that more ventilation leads to more oxygen in the lungs and in the bloodstream. In other words, the more oxygen we have in the lungs and in the blood, the less oxygen the cell receives.

In the Bohr effect, more oxygen is released to those tissues with higher carbon dioxide concentrations. The sensitivity to these effects can be suppressed in chronic diseases, leading to decreased oxygenation of peripheral tissues. Chronic conditions such as asthma, cystic fibrosis, or even diabetes mellitus, can lead to a chronic state of hyperventilation in order to maintain adequate tissue oxygenation. These states can have ventilation of up to 15 L per minute compared to the average normal minute ventilation of 6 L per minute.

This hyperventilation minimizes the potential of the Bohr effect through excess exhalation of carbon dioxide resulting in hypocapnia, causing a left shift the oxygen dissociation and unnecessarily increased oxygen-hemoglobin binding affinity with impaired oxygen release to peripheral tissues, including our most vital organs (brain, heart, liver, kidney). Thus, the Bohr effect is essential in maximizing oxygen transport capabilities of hemoglobin and functionally dynamic oxygen-binding/release secondary to carbon dioxide equilibrium.