Question

Glutamic acid: hydrophilic or hydrophobic? __________________ positive, negative, or neutral? ________________ valine: hydrophilic or hydrophobic? __________________ positive, negative, or neutral? ________________

Answer 1

Glutamic acid is a hydrophilic amino acid. At physiological pH, it is negatively charged. Carboxylic acid group ( -COOH ) in its side chain is responsible for both, the hydrophilic nature as well as negative charge of the glutamic acid. Because of  its hydrophilic nature it is found on the surface of protein facing aqueous solution i.e. it is an extrinsic amino acid.

Valine on the other hand is a hydrophobic amino acid. It is neutral at physiological pH. Valine has an aliphatic side chain which is responsible for both, it's hydrophobic nature as well as neutral charge. Since it is hydrophobic, it is found inside of protein molecules i.e. it is an intrinsic amino acid.