Which of the following contributes to the double helical structure of DNA ?

• Hydrogen bond

• Covalent bond

• Disulphide bond

• van der Waals' force

322.

A tripeptide is written as glycine-alanine -glycine. The correct structure of the tripeptide is

• 

• 

• 

• 

Which of the following compound shows aromatic properties ?

• Valine

• Leucine

• Serine

• Tyrosine

Amino acids have peptide linkage which is :

• -CO-NH-

• -C-NH₂

• SO-NH-

• -CO-N-

The non-essential amino acid among the following is:

• Leucine

• Alanine

• Lysine

• Valine