Which of the following statements describes the oxygen binding curve of hemoglob

Question

Which of the following statements describes the oxygen binding curve of hemoglobin? Each of the four oxygens bind with equal facility The binding of the first oxygen molecule enhances the binding of the other three oxygen molecules The binding of the first oxygen molecule makes the binding of the other three oxygen molecules more difficult The binding of the first oxygen molecule has no effect on the binding of the remaining three oxygen molecules Each successive oxygen bound makes the remaining sites less likely to bind oxygen. The substitution of Val for Glu in the sixth position of the beta-chain 6f hemoglobin produces sickle-cell anemia in the homozygote because: The Val-6 variant loses solubility upon deoxygenation and beta-chains aggregate The cooperative binding of oxygen is lost because of the missing Glu-6 residue The red cell is unable to sequester high enough concentrations of the Val-6 variant hemoglobin The apoprotein can no longer protect the heme iron from becoming oxidized owing to the presence of the hydrophobic Val-6 The Val-6 variant tends to retain oxygen when the oxygen tension is low According to the symmetry model for allosteric proteins, which of the following statements is true for hemoglobin? Each of the four subunits in hemoglobin changes one at a time from the low affinity to the high affinity state The alpha subunits, then the beta subunits change from the low affinity to the high affinity state Each ofthe four subunits in the hemoglobin tetramer is either the low affinity state or the high affinity state The alpha subunits have low affinity and the beta subunits have high affinity for oxygen

Explanation / Answer

Q.8: From the oxygen binding curve of hemoglobin it can be concluded that the binding of the first oxygen molecule enhances the binding of three other oxygen molecules. Hence option (b) is correct.

Q.9: The val - 6 variant loses its solubility upon deoxygenation and beta - chains aggregate due to substitution of Val for Glu in the sixth position of the beta - chain of hemoglobin. This causes sickel - cell anemia. Hence option (a) is correct.

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