myoglobin-keyproperties-資料下載頁
2024-10-24 17:26本頁面
【導(dǎo)讀】8a-helices(A,B,C,…Fe(II)stateisactive,Fe(III)[oxidized]. Fe(II)atominhemebindsO2. limitingtheir. vitalO2capacity.Mb+O2?MbO2. IfKd(dissociation)ishigher,bindingisweaker. Kd/Kd=[Mb]/[MbO2]=1……[Mb]=[MbO2]. Mb+O2?MbO2,Kd=[Mb][O2]/[MbO2]. O2isagas:express[O2]aspartialpressure(pO2). AspO2increases,bindingincreases. enzymes!!!)[Draw]. LowpO2?HighpO2?Athalf-saturationpO2=Kd,fieldusestermP50. P50(myoglobin)=torr/pO2=10-100torrin-vivo!!aandbchains44%identical. a1b1(a2b2)-35residues,a1b2(a2b1)-19residues. Hb+nO2?Hb(O2)1+Hb(O2)2+Hb(O2)3+Hb(O2)4. [How’sthatforplicated!?!?!YO2=[Hb(O2)1+….]/([Hb]+[Hb(O2)1+…Bindingcurveis. Arte
【正文】 n. 3. In parallel, CO2 diffuses from blood into the alveoli. 4. The lower concentration of dissolved CO2 in the blood causes lower pH (~) in lungs than in the peripheral tissues (~pH ) where CO2 is being actively released. A. High pO2 / high pH Why O2 Transport Works 5. Red blood cells (containing O2hemoglobin) carried to the peripheral tissues. B. pO2 decreases because O2 USED by the tissues. C. Blood plasma bees more acidic (lower pH) because CO2 is released. The bination of lower pO2 and pH in the peripheral tissues causes a large decrease in O2 saturation. O2 is released by hemoglobin!!!! Note: changes in pO2 and pH are small! Why Myoglobin in Muscle? ? Under resting conditions, O2 saturation is at point X on the green curve ? Small changes in pO2 and pH have very little effect on saturation ? During extremely vigorous exercise, heart pumps blood fast and breathing is rapid to increase the intake of O2 . Also, pH is lowered. ? Eventually, transport not fast enough to meet needs, . pO2 lowered because O2 is used faster than it can be replenished. [Hemoglobin now no help!] ? Under extreme conditions, shift from point X to Y: saturation of the myoglobin is lowered = release of O2. Defects from Hemoglobin Mutations 1. Weakened heme binding. 2. Disruption of secondary structure. 3. Disruption of quaternary structure. 4. Defective oxygen transfer. 5. Altered affinity for oxygen. 6. Oxidation of Fe(II) to Fe(III). 7. Aggregation in the T state (Hemoglobin S). Sickle cell anemia results from aggregation of Hb into insoluble fibers causing mishapen blood cells that cannot pass through capillaries and block blood flow to tissues.
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