Search results
Results from the WOW.Com Content Network
Hemoglobin in organisms at high altitudes has also adapted such that it has less of an affinity for 2,3-BPG and so the protein will be shifted more towards its R state. In its R state, hemoglobin will bind oxygen more readily, thus allowing organisms to perform the necessary metabolic processes when oxygen is present at low partial pressures. [74]
The T state has a lower affinity for oxygen than the R state, so with increased acidity, the hemoglobin binds less O 2 for a given P O2 (and more H +). This is known as the Bohr effect . [ 4 ] A reduction in the total binding capacity of hemoglobin to oxygen (i.e. shifting the curve down, not just to the right) due to reduced pH is called the ...
When hemoglobin is in its T state, the N-terminal amino groups of the α-subunits and the C-terminal histidine of the β-subunits are protonated, giving them a positive charge and allowing these residues to participate in ionic interactions with carboxyl groups on nearby residues. These interactions help hold the haemoglobin in the T state.
In the historical model, each allosteric unit, called a protomer (generally assumed to be a subunit), can exist in two different conformational states – designated 'R' (for relaxed) or 'T' (for tense) states. In any one molecule, all protomers must be in the same state. That is to say, all subunits must be in either the R or the T state.
The R state, with oxygen bound to a heme group, has a different conformation and does not allow this interaction. By itself, hemoglobin has sigmoid-like kinetics. In selectively binding to deoxyhemoglobin, 2,3-BPG stabilizes the T state conformation, making it harder for oxygen to bind hemoglobin and more likely to be released to adjacent tissues.
Thus, the Haldane effect describes the ability of hemoglobin to carry increased amounts of carbon dioxide (CO 2) in the deoxygenated state as opposed to the oxygenated state. Vice versa, it is true that a high concentration of CO 2 facilitates dissociation of oxyhemoglobin, though this is the result of two distinct processes (Bohr effect and ...
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
Change in oxygen affinity: High or low oxygen affinity Hb molecules are more likely than normal to adopt the relaxed (R, oxy) state or the tense (T, deoxy) state, respectively. High oxygen affinity variants (R state) cause polycythemia (e.g., Hb Chesapeake, Hb Montefiore).