Life sciences · the experiment
Tune hemoglobin's cooperativity
One hemoglobin, its four sites and only the oxygen molecules it carries, in a small closed volume. Tune its cooperativity, then make it hand over its oxygen like blood travelling from the lungs to the muscles.
1 · The best fit
Beginner
Fitted to the same saturation data, what cooperativity factor α does the canonical framework give Pauling's model?
K stays at 71.33, the value of the article's fit. Tune α until each of the four levels g[n] falls inside its window, the pressure range in which hemoglobin should give up that molecule.
2 · Deliver the oxygen
Intermediate
A molecule leaves hemoglobin when its level g[n] rises above the plasma threshold, ν₀ + ln(p / 100 torr), with ν₀ = −3.62. With the article's fit, g[3] = −4.67: below roughly what pressure does the second molecule leave?
With the article's fit (α = 1.88, K = 71.33), lower the plasma oxygen pressure, as when blood moves from the lungs to a muscle, until hemoglobin has given up two molecules and still holds two.
3 · Too much cooperativity
Expert
Another setting of the same model, taken from the article: α = 4.83 and K = 13. The levels are g[4] = −4.32, g[3] = −4.04, g[2] = −4.23 and g[1] = −3.97. What happens as the pressure drops?
Same model, set this time with α = 4.83 and K = 13. Lower the pressure slowly and stop as soon as hemoglobin gives up its oxygen.
4 · And without cooperativity?
Expert
Without cooperativity (α = 1, K ≈ 200), g[4] falls inside its window, but g[3], g[2] and g[1] sit below theirs. Which tissues does this hemoglobin serve?
Cooperativity tuned
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