What is the Bohr effect?
The Bohr effect is a way to explain the cell’s oxygen release. Red blood cells don’t load oxygen into tissues. Carbon dioxide (CO2) plays a key role in O2 transport due vasodilation. Christian Bohr, a Danish physiologist and father of Niels Bohr, first described the Bohr law in 1904.
Bohr effect in healthy people
Bohr’s effect is normal in healthy people, since healthy people have normal breathing patterns at rest and normal arterial CO2 levels. How does the Bohr law operate? We know that hemoglobin, which is found in red blood cells and called “erythrocytes”, transports oxygen in the blood. How does hemoglobin in red blood cells (called “erythrocytes”) know which areas to release more oxygen and which ones to keep it down? Or, why do they release more oxygen? Why is O2 being released into tissues? Red blood cells detect higher levels of CO2 in tissues, and release oxygen at these locations.
Bohr effect summary. Tissues with higher relative and absolute CO2 values release more oxygen. This is true even for people with normal breathing patterns.
Chronic diseases: The suppressed Bohr effect
Are people with chronic illnesses able to enjoy the normal Bohr effect? Can they still receive oxygen to their brains, hearts, and other vital organs? These medical studies are worth looking at.
Note that advanced stages of some conditions (e.g., asthma and CF) can lead to lung destruction, ventilation-perfusion mismatch and arterial hypercapnia, causing a further reduction in body oxygen levels.
Overbreathing or hyperventilation in the sick causes hypocapnia or reduced CO2 tension in the lungs and arterial blood (since ventilation-perfusion mismatch is not a common finding in the sick). This causes a reduction in oxygen release and cell oxygen tension (Aarnoudse, Monday & Treault, 1980; Gottstein, 1976).
The suppressed Bohr Effect is therefore caused by a low absolute CO2 concentration (see the image to the right), and O2 molecules remain attached to red blood cells. This effect is called “increased oxygen affinity for hemoglobin” by scientists. Hypoxia (CO2 deficiency) can lead to hypoxia (the suppressed Bohr Effect). The oxygen available in vital organs like the brain, heart and kidneys decreases the more we breathe at rest.
Many believe that more oxygen in the air will increase cell’s oxygen content. This is false. In fact, even though breathing is more efficient than usual, it can actually reduce the oxygen content of the arterial blood. Red blood cells are 98% saturated with oxygen in hemoglobin, which is healthy for normal breathing. This number drops to 98% when we hyperventilate (it actually gets lower in real life as most people transition to automatic chest or costal breathing, which reduces arterial blood oxygen levels). However, without CO2 or the Bohr effect, the oxygen is tightly bound to red blood cells and is unable get into the tissues in the required quantities. We now know the reason heavy breathing causes a drop in the cell-oxygen levels of all vital organs.
Our survival depends on the Bohr effect. Why? Some organs and tissues produce more CO2 than others. Red blood cells sense these additional CO2 concentrations and release more O2 to the areas that require it most. This smart self-regulating mechanism allows cells to efficiently transport oxygen.
Bohr effect (medical and scientific explanation).
Christian Bohr said that hemoglobin would be less able to bind oxygen at lower pH levels (e.g. in tissues). According to the Bohr Effect, carbon dioxide is directly in equilibrium with blood protons. This causes hemoglobin to be less able to bind to oxygen in lower pH environments (e.g., tissues or capillaries).
Nearly all textbooks on physiological science contain a description of the Bohr Effect, which is a physiological law. Modern research on the Bohr Effect focuses on more complex topics. See the titles of modern studies below. The Bohr effect’s central idea is that oxygen affinity to hemoglobin is dependent on oxygen concentrations. Lower CO2 values reduce oxygen delivery to the body cells.
Bohr effect, physical exercise
Without the Bohr effect , it would be impossible to walk or run even for 3-5 minutes. Why? Bohr effect: In normal conditions, the Bohr effect causes more oxygen to be released into muscles which produce more CO2. These muscles can still work at a high rate.
Sick people, however, have lower CO2 blood levels. They are more likely to feel chronic fatigue and have poor results in physical fitness tests. This is due to tissue hypoxia, or low cell-oxygen levels.
Professor Henderson on the Bohr effect
This is Professor Henderson, Yale University’s article on the Bohr effect.
“But even in 1885, Miescher (Swiss physician) was inspired by the insight of genius and wrote: “Over O2 supply of body, CO2 spreads it protecting wings.”Yandell Henderson (1873-1944), Henderson Y, carbon dioxide, in Cyclopedia of Medicine ed. H.H. Young, Philadelphia, FA Davis, 1940.
This YouTube video explains why excessive breathing can cause a decrease in cell-oxygen levels.
However, it is known that many of the Bohr Effect studies were conducted in vitro. It is not yet clear whether hyperventilation or arterial hypocapnia (low carbon dioxide) actually cause decreased oxygen transport. I will explain this in the bonus content below.
Vasodilation is more likely to be the main factor in oxygen transport in living organisms than the Bohr Effect. Bohr’s effect has a problem. People hyperventilate which reduces CO2 but also slows down blood circulation (circulation). Overbreathing causes tissues to accumulate more CO2, while the blood flow is slower. The Bohr effect’s true value isn’t as great as people think, but vasodilation reduces O2 and blood supply for all cells.
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