(a) Name the type of linkages responsible for the formation of primary and secondary structures of proteins.
(b) On electrolysis in acidic solution, `alpha`-amino acids migrate towards cathode while in alkaline medium, they migrate towards anode. Explain.
(c ) What are essential and non-essential amino acids ? Give two examples of each

Explanation

(a) Peptide linkages `(-CO-NH-)` are present in the primary structures of proteins while the secondary structures of proteins involve hydrogen bonding.
(b) An `alpha`-amino acid has a dipole a structure. In acidic medium, it exists as a positive ion.
`underset("Dipolar ion")(H_(3)overset(+)(N)-overset(H)overset(|)underset(R )underset(|)(C )-COO^(-))+underset(("Acid"))(H^(+))rarr underset(("Positive ion"))(H_(3)overset(+)(N)-overset(H)overset(|)underset(R )underset(|)(C )-COOH)`
In electric field, the positive ion moves towards cathode. In alkaline medium, the dipolar ion changes to anion and moves towards anode under the influence of applied electric field.
`H_(3)overset(+)(N)-overset(H)overset(|)underset(R )underset(|)(C )-COO^(-)underset(("Base"))(OH^(-))rarr underset(("Negative ion"))(H_(2)N-overset(H)overset(|)underset(R )underset(|)(C )-COO^(-))+H_(2)O`
(c) Amino acids which are not synthesised by the body are called essential amino acids. For example, Leucine and Lysine. Amino acids which are synthesised by the body are known as non-essential amino acids. For example, Glycine and Alanine.