Question

show work please

5) Consider the phenolic hydroxyl group of a particular Tyr residue in a protein. Suppose the hydroxyl group in the unfolded protein in aqueous solution, where the group is exposed to H20, has a pka of 10.0. If that group is found in a hydrophobic environment in the interior of the protein when the protein is folded into its native tertiary structure, would you expect the pka of the phenolic hydroxyl to be higher or lower in the folded protein interior than in H2O? Explain your reasoning. (2 pt)

Answer 1

The phenolic hydroxyl group in Tyr residue has pka of 10.0 when exposed to water.

Water has a pka of 14 which means in presence of water phenolic OH of Tyr can behave as a stronger acid and loose its proton easily.

In the interior of the protein in folded state, where there is absence of water, there is lesser driving force for phenolic OH to donate its ionisable proton, so its acidity should be lowered which means pka should be higher.