Which macromolecule is characterized by a repeating pattern of N-C-C in its polypeptide chain?

The correct answer is indeed proteins. Proteins are composed of polypeptides, which are chains of amino acids linked together by peptide bonds. The repeating pattern of N-C-C in the polypeptide chain refers specifically to the backbone structure of amino acids, where 'N' represents the nitrogen atom in the amino group, 'C' corresponds to the alpha carbon of the amino acid, and the second 'C' denotes the carbonyl carbon in the carboxyl group.

This N-C-C pattern is characteristic of all amino acids, the building blocks of proteins. Each amino acid has this basic structure, with varying side chains that define the properties and functions of each specific amino acid. As polypeptides fold and combine, they create the diverse range of proteins that perform countless functions in biological systems, from catalyzing reactions as enzymes to providing structural support in cells.

In contrast, carbohydrates consist primarily of sugar units, lipids are made up of fatty acid chains, and nucleic acids are polymers of nucleotides. None of these other macromolecules feature the specific N-C-C repeating pattern found in polypeptides, which is why proteins are the correct answer to this question.