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Science Of CO2Lift

Science of CO2Lift

Learn the Science Behind the Carboxy Treatment

Bohr Effect

The Bohr effect is a physiological phenomenon first described in 1904 by the Danish physiologist Christian Bohr (father of physicist Niels Bohr and so grandfather of physicist Aage Bohr), stating that hemoglobin’s oxygen binding affinity is inversely related both to acidity and to the concentration of carbon dioxide.[1] That is to say, a decrease in blood pH or an increase in blood CO2 concentration will result in hemoglobin proteins releasing their loads of oxygen and a decrease in carbon dioxide or increase in pH will result in hemoglobin picking up more oxygen. Since carbon dioxide reacts with water to form carbonic acid, an increase in CO2 results in a decrease in blood pH.

The Bohr effect explains cells oxygen release or why red blood cells unload oxygen in tissues, while carbon dioxide (CO2) is the key player in O2 transport due to vasodilation and the Bohr effect (or Bohr law).

The Bohr effect is a normal process in healthy people since healthy people have normal breathing at rest and normal arterial CO2 levels. How does the Bohr effect work? As we know, oxygen is transported in blood by hemoglobin cells. How do these red blood cells know where to release more oxygen and where less? Or why do they unload more oxygen at all? Why is O2 released in tissues? The hemoglobin cells sense higher concentrations of CO2 in tissues and release oxygen in such places.

Mechanism

In deoxyhemoglobin, the N-terminal amino groups of the α-subunits and the C-terminal histidine of the β-subunits participate in ion pairs. The formation of ion pairs causes them to decrease in acidity. Thus, deoxyhemoglobin binds one proton (H+ ) for every two O2 released. In oxyhemoglobin, these ion pairings are absent and these groups increase in acidity. Consequentially, a proton is released for every two O2 bound. Specifically, this reciprocal coupling of protons and oxygen is the Bohr effect.[2]

Additionally, carbon dioxide reacts with the N-terminal amino groups of α-subunits to form carbamates: [3] R−NH2 + CO2 R−NH−COO- + H+.

Deoxyhemoglobin binds to CO2 more readily to form a carbamate than oxyhemoglobin. When CO2 concentration is high (as in the capillaries), the protons released by carbamate formation further promotes oxygen release. Although the difference in CO2 binding between the oxy and deoxy states of hemoglobin accounts for only 5% of the total blood CO2, it is responsible for half of the CO2 transported by blood. This is because 10% of the total blood CO2 is lost through the lungs in each circulatory cycle.[4]

Physiological Role

This effect facilitates oxygen transport as hemoglobin binds to oxygen in the lungs, but then releases it in the tissues, particularly those tissues in most need of oxygen. When a tissue’s metabolic rate increases, its carbon dioxide production increases. Carbon dioxide forms bicarbonate through the following reaction: CO2 + H2O H2CO3 H+ + HCO3 − Although the reaction usually proceeds very slowly, the enzyme family of carbonic anhydrase, which is present in red blood cells, accelerates the formation of bicarbonate and protons. This causes the pH of tissues to decrease, and so, promotes the dissociation of oxygen from hemoglobin to the tissue, allowing the tissue to obtain enough oxygen to meet its demands. Conversely, in the lungs, where

Although the reaction usually proceeds very slowly, the enzyme family of carbonic anhydrase, which is present in red blood cells, accelerates the formation of bicarbonate and protons. This causes the pH of tissues to decrease, and so, promotes the dissociation of oxygen from hemoglobin to the tissue, allowing the tissue to obtain enough oxygen to meet its demands. Conversely, in the lungs, where oxygen concentration is high, binding of oxygen causes hemoglobin to release protons, which combine with bicarbonate to drive off carbon dioxide in exhalation. Since these two reactions are closely matched, there is little change in blood pH. The dissociation curve shifts to the right when carbon dioxide or hydrogen ion concentration is increased. This facilitates increased oxygen dumping. This mechanism allows for the body to adapt the problem of supplying more oxygen to tissues that need it the most. When muscles are undergoing strenuous activity, they generate CO2 and lactic acid as products of cellular respiration and lactic acid fermentation. In fact, muscles generate lactic acid so quickly that pH of the blood passing through the muscles will drop to around 7.2. As lactic acid releases its protons, pH decreases, which causes hemoglobin to release ~10% more oxygen.[4] (2) ^

Murray, Robert K.; Darryl K. Granner, Peter A. Mayes, Victor W. Rodwell (2003). Harper’s Illustrated Biochemistry (LANGE Basic Science) (26th ed.). McGraw-Hill Medical. pp. 44–45. (3) ^ Lehninger, Albert L.; Nelson, David L.; Cox, Michael M. (2008). Principles of Biochemistry (5th ed.). New York, NY: W.H. Freeman and Company. p. 166. (4) ^ a b Voet, Donald; Judith G. Voet, Charlotte W. Pratt (2008). Fundamentals of Biochemistry: Life at the Molecular Level (3rd ed.). John Wiley & Sons. pp. 189–190.

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