Question

Refer to the chart of amino acid structures to help answer this question. Which four statements about amino acids are true? Ser and Gln are polar amino acids. The Leu side chain does not form hydrogen bonds with other amino acids. The form of glycine used by the human body is D‑glycine. Methionine is a thiol. Phe can undergo oxidation to form Tyr. Proline has an overall charge at physiological pH (7.4). Lysine has one stereocenter (chiral center).

Answer 1

Answer:

1. Ser and Gln are polar amino acids.

2. The Leu side chain does not form hydrogen bonds with other amino acids.

3. Phe can undergo oxidation to form Tyr.

4. Lysine has one stereocenter (chiral center).

Explanation:

Serine and glutamine are the polar amino acids with uncharged side group. Serine has a "CH2OH" group as its side chain and the presence of hydroxyl group makes it a polar amino acid. Glutamine is one of the amides derived from other amino acids present in proteins.  

Leucine is a nonpolar amino acid with an aliphatic side chain and tends to cluster within the proteins to stay away from the surrounding watery medium. Its aliphatic R group does not form any hydrogen bonds to other amino acids.  

Phenylalanine is a nonpolar amino acid with an aromatic R group. Oxidation of aromatic R group of phenylalanine converts it into tyrosine which has an additional hydroxyl group in its side chain.

The chiral center is the carbon to which four different functional groups are bonded. The central alpha carbon atom of lysine is bonded to an amino group, carboxyl group, a hydrogen atom, and one positively charged R group which in turn makes it a chiral center.