The non-essential amino acid among the following is:

• Leucine

• Alanine

• Lysine

• Valine

Amino acids have peptide linkage which is :

• -CO-NH-

• -C-NH₂

• SO-NH-

• -CO-N-

Which of the following compound shows aromatic properties ?

• Valine

• Leucine

• Serine

• Tyrosine