Proteins

Amino acids have a characteristic side chain (R group) that determines their properties. Polar R groups contain atoms that can form hydrogen bonds, making them hydrophilic. - Alanine has a non-polar R group (methyl group), making it non-polar.
- Valine also has a non-polar R group (isopropyl group), making it non-polar.
- Glycine has a hydrogen atom as its R group, but it is considered non-polar.
- Glutamine, on the other hand, has an amide group as its R group, which is polar and hydrophilic. Therefore, the correct answer is option (D).

Essential amino acids are those that cannot be synthesized by the body and must be obtained from the diet.
Let's examine the given amino acids:
(i) Leucine – Essential amino acid.
(ii) Glutamic acid – Non-essential amino acid.
(iii) Asparagine – Non-essential amino acid.
(iv) Valine – Essential amino acid.
Thus, the correct answer is option D, as Leucine and Valine are essential amino acids.