In the native form of a simple, globular protein in aqueous solution, the charged groups:
A) have pK's below the solution pH
B) are mostly involved in intramolecular electrostatic bonds.
C) are almost all on the surface of the molecule.
D) are completely accounted for by the side chains of the basic and acidic amino acids.
E) All of the above.

Question

Quizplus · Accepted Answer

In the native form of a simple, globular protein in aqueous solution, the charged groups are almost all on the surface of the molecule. This is because the non-polar amino acid side chains are buried inside the protein, while the polar (but uncharged) and charged amino acid side chains are on the surface where they can interact with water. The pK's of the charged groups may be below or above the solution pH, depending on the specific amino acid side chains involved. Intramolecular electrostatic bonds may be present, but not mostly involving charged groups. The charged groups are not completely accounted for by the side chains of the basic and acidic amino acids, as there may be other charged groups present such as those from histidine or cysteine. Therefore, only choice C is correct.

In the Native Form of a Simple, Globular Protein in Aqueous