Hemoglobin Tetramer [Hb(O 2 )] [Hb]P O 2 K 2 = [Hb(O 2 )] [Hb]P O 2 K 3 = [Hb(O 2 )] [Hb]P O 2 K 4 = [Hb(O 2 )] [Hb]P O 2 K 1 = = 4.88 = 15.4 = 6.49 = 1750 Whole blood can carry as much as 0.01 moles of O 2 . Plasma can carry only 0.0001 moles of O 2 Hb (aq) + O 2(g) Hb(O 2 ) (aq) Hb(O 2 ) (aq) + O 2(g) Hb(O 2 ) 2( Hb(O 2 ) 2(aq) + O 2(g) Hb(O 2 ) Hb(O 2 ) 3(aq) + O 2(g) Hb(O 2 ) 4
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Hemoglobin Tetramer [Hb(O 2 )] [Hb]P O 2 K 2 = [Hb(O 2 )] [Hb]P O 2 K 3 = [Hb(O 2 )] [Hb]P O 2 K 4 = [Hb(O 2 )] [Hb]P O 2 K 1 = = 4.88 = 15.4 = 6.49 =
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Hemoglobin Tetramer
[Hb(O2)]
[Hb]PO2
K2 =
[Hb(O2)]
[Hb]PO2
K3 =
[Hb(O2)]
[Hb]PO2
K4 =
[Hb(O2)]
[Hb]PO2
K1 = = 4.88
= 15.4
= 6.49
= 1750
Whole blood can carryas much as 0.01 moles of O2. Plasma can carryonly 0.0001 moles of O2
Hb(aq) + O2(g) Hb(O2)(aq)
Hb(O2)(aq) + O2(g) Hb(O2)2(aq)
Hb(O2)2(aq) + O2(g) Hb(O2)3(aq)
Hb(O2)3(aq) + O2(g) Hb(O2)4(aq)
Myoglobin Tetramer
[Mb(O2)]
[Mb]PO2
K = = 271
Mb(aq) + O2(g) Mb(O2)(aq)
Change the partial pressure of O2 will shift the equilibrium.Increasing PO
2 will shift the equilibrium to the right, decreasing PO
2
will shift the equilibria to the left.
• Myoglobin– Higher affinity for O2 (low
PO2)
– Hyperbolic binding– O2:Mb 1:1– Binds O2 in tissues
• Hemoglobin– Lower affinity for O2 (High
PO2)
– sigmoidal binding– O2:Hb 4:1– Binds O2 in lungs,
releases in tissues
At a PO2 of 0.13 atm both hemoglobin and myoglobin are 95% saturated. With a
PO2 of 0.040 atm hemoglobin is only 55% saturated whereas myoglobin is above
90%. Thus, as PO2 decreases in the capillaries hemoglobin releases almost half