What Is Bohr Effect?
Bohr Effect, one of the prominent discoveries in the field of medical sciences, was first described by a physiologist namely, Christian Bohr in 1904. Bohr Effect is a phenomenon that gives us an explanation of changes in hydrogen ion and carbon dioxide concentration shift oxygen-hemoglobin dissociation curve.
It explains why RBCs in our body pick up and releases oxygen. Bohr Effect is a very essential process of physiology as it explains how does oxygen is picked up by the hemoglobin-containing RBCs and how does red blood cells, also called as erythrocytes release oxygen into the bloodstream. Also, with the help of vasodilation process (a process by the virtue of which the blood vessels become relaxed and this leads to the decrease of the blood pressure), Carbon dioxide plays a very important role in the transportation of the oxygen to the other tissues in the body.
Oxygen-Hemoglobin Dissociation Curve – Explanation
Bohr Effect explains how does the affinity of the oxygen to get bind to hemoglobin is related to the acidity levels in the cells and the levels of carbon dioxide in the tissue. Well, there is an inverse relationship between the oxygen binding affinity with hemoglobin and the acidity as well as the carbon dioxide concentration in the tissues.
The explanation of this process goes as follows:
- The oxyhemoglobin is formed when there is the low concentration of carbon dioxide and hydrogen ions (H+ ions) and therefore low acidity in the surrounding medium and the cell.
- When there is a higher concentration of carbon dioxide and Hydrogen ions in the cell it leads to the breaking down of oxyhemoglobin thereby triggering the release of oxygen.
- Hence, at the partial pressure of oxygen, due to the concentration of carbon dioxide, there is a shift in the curve of oxyhemoglobin and this is known as Bohr Effect.
Percentage Saturation – it is determined by the amount of oxygen taken up by hemoglobin at particular time for the formation of oxyhemoglobin.
Oxygen-Hemoglobin Dissociation Curve refers to the graph plotted which shows the pattern of saturation in the affinity of oxygen binding to hemoglobin as the partial pressure of oxygen elevates. The shape of this curve is Sigmoid i.e. S-shaped. By this curve, we can conclude that the oxygen readily binds with hemoglobin due to its higher affinity to get bind with oxygen.
The partial pressure of oxygen in the blood cells of the human artery is about 95-100 mmHg. At this particular pressure, there is 97% saturation of oxygen binding to that of hemoglobin. This indicates that it is naturally favorable for the oxyhemoglobin to get formed. Similarly, the partial pressure of oxygen in veins is 40 mmHg. Hence, the binding affinity of hemoglobin with oxygen decreases and hence the saturation level drops down to 70%.
The Physiological Importance Of Bohr Effect
The Bohr Effect is responsible for the increase in the efficiency of transportation of oxygen through the bloodstream. Hence, with the help of this phenomenon, we can explain why the oxygen is released through the bloodstream so as to reach the tissues which require oxygen from the lungs (where oxygen binds the hemoglobin due to higher concentrations of oxygen in the cells).
When the metabolism of a particular tissue is increased, there is an elevation in the carbon dioxide production in the cells. And when the CO2 is released into the blood, then carbon dioxide combines with water to form bicarbonate ions and protons are released.
The reaction takes place as follows
co2+H20↔H2CO3 ↔H+ + HCO3-
This reaction has a very slow speed of occurrence but it is facilitated multiple times by the presence of the carbonic Anhydrase enzyme which causes a decrease in the pH of the blood and therefore, facilitates the dissociation of oxygen and hemoglobin. This enables the surrounding tissues to meet their demands by consuming the dissociated oxygen and the reverse process takes place in the lungs where the oxygen concentration is higher.
Therefore, we can conclude that Bohr Effect allows the adaptation process to occur as a result of changing condition (unfavorable) so as to fulfill the requirement of the oxygen by the tissues for meeting its demands. For instance, when we are exercising and our muscles are continuously working, then the muscle cells require more oxygen for respiration process. Then, the Carbon dioxide is released as the waste and hence bicarbonate ions and protons are released. This leads to the decrease in the pH levels of the blood, and hence the occurrence of Bohr effect.
What is Haldane Effect?
The Haldane Effect is a phenomenon that explains one of the several properties of Hemoglobin which was first discovered by John Scott Haldane. It explains how oxygen concentration affects hemoglobin affinity towards carbon dioxide.
It explains how does carbon dioxide binds with hemoglobin when oxygen gets released and carbon dioxide gets released when the oxygen gets bind to the hemoglobin. Haldane Effect is very much similar to the Bohr Effect which makes it very much clear that the gases, carbon dioxide and oxygen both are the strong competitors for the binding to hemoglobin. This effect promotes the facilitation of exchange of both the gases i.e. carbon dioxide and oxygen in the circulation of blood, both through pulmonary pathways as well as peripheral routes of blood circulation.
Why Does Haldane Effect Occur?
The Haldane Effect occurs as a result of two effects which occur when the hemoglobin binds with oxygen.
When the oxygen binds to hemoglobin in lungs, it leads to the decrease in the affinity of the hemoglobin to bind to carbon dioxide and hence carbon dioxide gets released. In return, as a consequence of this process, the carbon dioxide will remain free because of the poor affinity of carbon dioxide to get bind with hemoglobin and hence the carbon dioxide will go to lungs from where it gets eliminated by the process of exhalation.
Carbaminohaemoglobin is a major contributor to Haldane effect because carbon dioxide binds with amino groups of hemoglobin to form carbaminohaemoglobin. When the oxygen binds with hemoglobin, then the acidity level rises due to release of protons in the bloodstream. This high concentration of protons in the cell will eventually promote the reverse equilibrium and hence, the bicarbonate ions will get converted into the carbon dioxide during the circulation in the Pulmonary artery and therefore, again it leads to the elimination of carbon dioxide from the lungs.
The Haldane effect gives us an explanation of how the oxygen exerts an effect on the transport of carbon dioxide. This explains that the hemoglobin in deoxygenated form has a higher affinity for carbon dioxide. It can be explained by the fact that carboxyhemoglobin is a better acceptor for the protons that are released when the carbon dioxide combines with water as compared to oxyhemoglobin. On the other hand, the oxygenated hemoglobin has a higher affinity for oxygen. This deoxygenation of hemoglobin leads to the right shift in the oxygen dissociation curve and more breakdown of Co2 which leads to the greater release of protons. This increase in protons will lead to increase in the amount of CO2 that can be carried by the hemoglobin-containing RBCs in the blood to the lungs where the CO2 is released out of the body through the process of exhalation.
Therefore, we can say that Haldane Effect, in addition to Bohr Effect enhances the release of oxygen at the site of tissues and therefore, enhances the level of uptake of oxygen at the lungs.
Therefore, both Bohr Effect and Haldane effect are vital processes for the healthy functioning of the cells in an individual and are important research milestones in the field of physiology.