Hemoglobin curve

In the hemoglobin curves, the change from A to B to C is termed a rightward shift. The farther to the right a curve is shifted, the larger is the P50 value and the lower is the oxygen affinity. In this example, the shift is due to an increase in Pco2 since pH, temperature, and 2,3-DPG concentration were held constant. However, the shift could also have been caused by an increase in temperature (as in strenuous exercise or fever), a decrease in pH (as in acidosis or exercise), an increase in 2,3-DPG concentration (see below), or a combination of these variables. For... 

The second feature is that the myoglobin curve is everywhere above the hemoglobin curve. In particular, at the low partial pressure of 20 torr, when the hemoglobin occupancy is very low 9 0.2), the myoglobin curve reaches a near-saturation value of 1. 

Fio. 13. EH in relation to pH at 30. Curve A is for native horse hemoglobin. Curve B is for horse hemoglobin in 4M Urea. Curve C is for horse heart myoglobin. From Taylor (196) and Taylor and Morgan (199). 

Fig. 1.2. Fractions of molecules of hemoglobin occupied by a different number of oxygen molecules (m f.) as a function of the fraction of occupied oxygen binding sites in hemoglobin. Curves are calculated by using parameters of the Adair equation given in Fig. 1.1.

We can determine quantitatively the physiological significance of the sigmoid nature of the hemoglobin oxygen-binding curve, or, in other words, the biological importance of cooperativity. The equation... 

The importance of the BPG effect is evident in Figure 15.35. Hemoglobin stripped of BPG is virtually saturated with Og at a pO of only 20 torr, and it cannot release its oxygen within tissues, where the jbOg is typically 40 torr. BPG shifts the oxygen saturation curve of Hb to the right, making the Hb an Og... 

FIGURE 9.18 The variation of the extent of saturation of myoglobin (Mb) and hemoglobin (Hbl with the partial pressure of oxygen. The different shapes of the curves account for the different biological functions of the two proteins. 

THE OXYGEN DISSOCIATION CURVES FOR MYOGLOBIN HEMOGLOBIN SUIT THEIR PHYSIOLOGIC ROLES... 

The 02-binding curve for myoglobin is hyperbolic, but for hemoglobin it is sigmoidal, a consequence of cooperative interactions in the tetramer. Cooperativ-ity maximizes the ability of hemoglobin both to load O2 at the PO2 of the lungs and to deliver O2 at the PO2 of the tissues. 

Figure 12, Heat denaturation curves of hemoglobin from three members of a family with Hb-Leslie, a newly discovered unstable variant with a deletion of residue 131 of the p-chain, G.P.Sr. has Hb-Leslie p-thalassemia the %Hb-Leslie is 85% (DEAE-Sephadex chromatography) Gr.P. has Hb-LesUe- Hb-C %Hb--Leslie is 28% M.B. fm Hb LesUe trait %Hb Leslie is 28%,...

The P02 of blood is the major factor determining the amount of oxygen chemically combined with hemoglobin, or the percent of hemoglobin saturation. The relationship between these two variables is illustrated graphically by the oxyhemoglobin dissociation curve (see Figure 17.6). This relationship is not... 

FIGURE 1.12 NO production from the addition of nitrate reductase (NR = 15mU/mL) to a solution containing 50 pM sodium nitrate and various concentrations of NADH. The curves from top to bottom were obtained in solutions containing 100, 50, 40, and 0 iM NADH. Hemoglobin (Hb) was introduced to quench the production of NO. (Reprinted with permission from Elsevier Publishing [117].)... 

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