In oxygenated hemoglobin, pKa = 6.6 for the histidine residues at position 146 o

Question

In oxygenated hemoglobin, pKa = 6.6 for the histidine residues at position 146 on the -chain. In deoxygenated hemoglobin, the pKa of these residues is 8.2. This data indicates that deoxygenated hemoglobin is a ____________1___________ acid than oxygenated hemoglobin. This change in the pKa of the histidine residues underlies the Bohr effect in which_____2_____ in the hydrogen ion concentration reduces the affinity of hemoglobin for O2. The binding of H+ to these His residues_____3_____ their interactions with______4______ residues via _______5____. Fill in the bank, Choices for each number are listed below. 1. Either Stronger or weaker 2. an increase or a decrease 3. increases or decreases 4. Which Amino Acid only 1 needed ( Ala, Arg, Asn, Asp, Cys, Gln, Glu, Gly, His, Ile,Lys, Met, Phe, Pro, Ser, Thr, Trp, Tyr, Val) 5. Dipole-Dipole Interactions, Hydrogen Bonds, Hydrophobic Interactions, Salt Bridges. Pick 1 View comments (1)

Explanation / Answer

This data indicates that deoxygenated haemoglobin is a weaker acid than oxygenated haemoglobin. This change in the pKa of the histidine residues underlies the Bohr Effect in which an increase in the hydrogen ion concentration reduces the affinity of haemoglobin for O2. The binding of H+ to these His residues increases their interactions with Alanine residues via Salt bridges.

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