Chemistry of Proteins and Hemoglobin.
1. Protein A has a binding site for ligand X with a Kdof 10-6M. Protein B has a binding site for ligand X with a Kdof 10-9M. Which protein has the higher affinity for ligand X?
2. What is the effect of the following changes on the O2 affinity of hemoglobin? (a) A decrease in blood pH from 7.4 to 7.2. (b) A decrease in the partial pressures of CO2in the lungs from 6 kPa (holding one\'s breath) to 2 kPa (normal). (c) An increase in the BPG level from 5 mM (normal altitudes) to 8 mM (high altitudes). For (c), also consider fetal hemoglobin.
3. Under appropriate conditions, hemoglobin dissociates into its four subunits. The isolated α subunit binds oxygen, but the O2-saturation curve is hyperbolic rather than sigmoid. In addition, the binding of oxygen to the isolated α subunit is not affected by the presence of H+, CO2, or BPG. What do these observations indicate about the source of the cooperativity in hemoglobin?