Phosphodiester bonds form the backbone of polynucleotides like DNA and RNA by linking the 3′ hydroxyl of one nucleotide to the 5′ phosphate of another. Option 2 is correct, as the other options involve different bond types.

Option Analysis

Option 1: Polypeptides

Polypeptides (protein chains) form via peptide bonds between the carboxyl group of one amino acid and the amino group of another, releasing water. No phosphate is involved, so phosphodiester bonds do not apply.​

Option 2: Polynucleotides

Correct. Phosphodiester bonds create the sugar-phosphate backbone in DNA/RNA. The 3′-OH of one deoxyribose/ribose attacks the 5′-phosphate of the next nucleotide, forming a 3’→5′ linkage and releasing pyrophosphate.

Option 3: Lipoproteins

Lipoproteins assemble lipids (e.g., triglycerides, phospholipids) with apoproteins via non-covalent interactions (hydrophobic, electrostatic). No phosphodiester bonds occur; phospholipids have phosphoester links internally, but not between protein and lipid.​

Option 4: Oligomers of Carbohydrates and Lipids

Carbohydrate oligomers (oligosaccharides) link via glycosidic bonds (acetal linkages between sugars). Lipid oligomers are rare, but glycolipids use glycosidic bonds to sugars—no phosphodiester bonds in either.​

The phosphodiester bond forms polynucleotides MCQ is key for NEET, GATE Life Sciences prep, testing nucleic acid structure vs proteins, lipids, carbs. It highlights the 3′-5′ linkage in DNA/RNA backbones.​

Backbone in Polynucleotides

Forms via dehydration between 3′-OH and 5′-PO4, stabilizing genetic material.

Why Not Other Biomolecules?

Peptide bonds in polypeptides; non-covalent in lipoproteins; glycosidic in carb oligomers.​

Master this for biomolecule chapters in competitive exams.