We have an instance of the blind leading the blind. This string has been a
continuum of misinformation. For example:
Patrick says "CO2 does not bind more tightly to hemoglobin than oxygen."
Jerorem replies "I don't remember binding parameters [sic] for CO2 versus
O2. But one hemoglobin can bind 4 oxygen and only 1 CO2.
Binding affinities and binding stochiometry are different parameters.
Apples and oranges.
High partial pressures (45 mmHg) of carbon dioxide facilitate the
dissociation of oxygen from oxyhemoglobin. In nature, this happens in
actively respiring tissues where partial pressures of oxygen are for
obvious reasons decreasing, the net result is the tissues get oxygen and
carbaminohemoglobin carries a molecule of carbon dioxide (and a proton)
away from the tissue. In the lungs where partial pressures of carbon
dioxide are typically a little lower (40 mm Hg versus 45 mm Hg Pco2),
oxygen partial pressures are larger and approach 100 mm Hg Po2. In the
lungs, oxygen displaces carbon dioxide to form oxyhemoglobin. The proton is
also released and it combines with bicarbonate to form carbonic acid which
breaks down to form more carbon dioxide and water.
It is called the Bohr effect, it can be found discussed in any number of
texts-biology, biochemistry, or physiology. Please check to see if I am
correct or if I am just making this up. ;-).
Comparative Animal Physiologist
Division of Sciences and Mathematics
University of the Virgin Islands
St. Thomas, USVI 00802
rhall at uvi.edu