Which of the following is the best practical reason, based on the lesson, to classify a polypeptide with 40 amino acids differently than a protein with 400 amino acids?

A 40-residue chain is often considered a peptide due to its small size and different folding/functional properties, whereas 400 residues fall well within the typical protein size range and usually has more complex structure and functions.

Only chains longer than 10,000 residues can be considered proteins; anything smaller is non-functional and nutritionally irrelevant.

There is no conceptual distinction; any chain with more than one amino acid is always classified as a protein regardless of length or function.

A 40-residue chain is automatically more nutritionally valuable than a 400-residue protein because shorter chains supply more nitrogen per gram.