Hemoglobin, oxygen dissociation curve

A 72-year-old woman with emphysema presents to the emergency room with fatigue and respiratory distress. Which set of arterial blood gas values below would represent her condition and reflect a shift of the hemoglobin oxygen dissociation curve to the right ... 

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

I. A 10-month-old child is being evaluated for the underlying cause of a hemolytic anemia. In the diagram shown below, the oxygen dissociation curve for hemoglobin in his erythrocytes is compared with the curve obtained with normal red cells. 

Hyperbolic shape of the enzyme kinetics curve Most enzymes show Michaelis-Menten kinetics (see p. 58), in which the plot of initial reaction velocity, v0, against substrate concentration [S], is hyperbolic (similar in shape to that of the oxygen-dissociation curve of myoglobin, see p. 29). In contrast, allosteric enzymes frequently show a sigmoidal curve (see p. 62) that is similar in shape to the oxygen-dissociation curve of hemoglobin (see p. 29). 

Figure 7.11 shows the oxygen dissociation curve of one such hemoglobin, Hb Rainier, where it is seen that this hemoglobin is still 50% saturated with oxygen at a p02 of about 12 mm Hg compared to 27 mm Hg in normal hemoglobin. The value of n in the Hill equation is 1.5 for this hemoglobin. 

Figure 2-4. Oxygen dissociation curve for adult hemoglobin (HbA) demonstrating the characteristics of allosteric positive comparativity. Right shift of the curve caused by het-erotrophic ligands and increased temperature leads to decreased oxygen affinity.

Early this century, A.V. Hill derived a useful equation that describes the oxygen dissociation curve of hemoglobin fairly accurately. It is... 

The observation by Chanutin and collaborators (CIO, S64) and by Benesch and Benesch (B25, B26) that 2,3-DPG (and also ATP and inositol hexaphosphate, or IHP) binds to hemoglobin resulting in a shift to the right of the oxygen dissociation curve has led to numerous reports which describe topics related to biochemical and medical aspects of the... 

Ascorbic acid appears to be toxic to certain tumor tissues however, it may increase the biological effectiveness of red blood cells by increasing the level of 2,3-diphosphoglycerate (30,31), 2,3-Diphosphoglycerate is essential to maintaining the normal oxygen dissociation curve of hemoglobin. This increase has been shown in vitro (30) and in vivo, in human subjects (31). 

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