Question

An amino acid is usually more soluble in aqueous solvent at pH extremes than it is at a pH near the isolelectric point of the amino acid. (Note that this does not mean that the amino acid is insoluble at a pH near its pI.)

Which of the following statements correctly explains this phenomenon?

(Select all that apply.)

A. The neutral charge of an amino acid molecule at its isoelectric point will make the molecule hydrophobic.
B. At pH extremes, the amino acid molecules mostly carry a net charge, thus increasing their solubility in polar solvent.
C. At very low or very high pH, the amino acid molecules have increased charge, thus form more salt bonds with water solvent molecules.
D. At pH values far from the isoelectric point, individual amino acid molecules have greater kinetic energy, thus more readily stay in solution.

Answer 1

Amino acids are more soluble in aqueous solvent at pH extremes due to their charged nature, which increases their solubility in polar solvents. The neutral charge of an amino acid at its isoelectric point makes it hydrophobic and less soluble. At very low or very high pH, amino acids have increased charge and form more salt bonds with water, increasing their solubility.

Step-by-step explanation:

This phenomenon can be explained by the properties of amino acids at different pH values. At the isoelectric point (pI), the amino acid is neutral, which makes it hydrophobic and less soluble in water (option A). At pH extremes, the amino acid molecules mostly carry a net charge, which increases their solubility in polar solvents (option B). In addition, at very low or very high pH, the amino acid molecules have increased charge and form more salt bonds with water solvent molecules, further enhancing their solubility (option C).

Answer 2

Option B. At pH extremes, the amino acid molecules mostly carry a net charge, thus increasing their solubility in polar solvent.

C. At very low or very high pH, the amino acid molecules have increased charge, thus form more salt bonds with water solvent molecules.

Step-by-step explanation: