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.
Additionally, carbon dioxide reacts with the N-terminal amino groups of α-subunits to form carbamates:
- 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.
Read more about this topic: Bohr Effect
Famous quotes containing the word mechanism:
“Life is an offensive, directed against the repetitious mechanism of the Universe.”
—Alfred North Whitehead (1861–1947)
“I’ve never known a Philadelphian who wasn’t a downright “character;” possibly a defense mechanism resulting from the dullness of their native habitat.”
—Anita Loos (1888–1981)
“The two elements the traveler first captures in the big city are extrahuman architecture and furious rhythm. Geometry and anguish. At first glance, the rhythm may be confused with gaiety, but when you look more closely at the mechanism of social life and the painful slavery of both men and machines, you see that it is nothing but a kind of typical, empty anguish that makes even crime and gangs forgivable means of escape.”
—Federico García Lorca (1898–1936)