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 =...

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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 = 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(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

Of the O2 which O2 poor myoglobin can pick up.