Question

Compare and contrast the bonds involved in formation of macromolecules, including proteins, nucleic acids and carbohydrates, with those involved in formation of macromolecular assemblies of lipids, e.g. membranes.

Answer 1

Macromolecules include proteins, nucleic acids, lipids, and carbohydrates. They are formed by the polymerization of smaller units called monomers.

Peptide bond -protein

Each amino acid has two functional groups- amine (-NH­₂) group, and the carboxylic acid (-COOH) group. A peptide bond is formed (-CONH) between the –NH₂ group and the –COOH group of any two adjacent amino acids and it leads to the elimination of a water molecule.

Glycosidic bond- carbohydrates

When two adjacent monosaccharide units link to form disaccharides or polysaccharides, a glycosidic bond is formed. Whenever a glycosidic bond is formed, there is the elimination of a water molecule similar to the formation of a peptide bond.

Phophodiester bond- nucleic acid

A phosphodiester bond is a covalent bond that is mainly found in nucleic acids(DNA and RNA) in which a phosphate group joins adjacent carbons through ester linkages.

Bonds involved in macromolecule assemblies of lipids

Lipids are joined together by ester linkages.

In membranes, the proteins and lipid molecules are held together by noncovalent interactions such as Van der Waals forces and hydrogen bonding, which help to stabilize the lipid bilayer structure.