Natural polyamide fibres: which of the following is correctly classified as a natural polyamide fibre?

Introduction / Context:
Polyamides can be synthetic (like nylons) or natural (like proteins). Natural fibres composed of proteins contain amide linkages in their backbone and are therefore polyamides by chemistry. The question asks you to select one natural polyamide fibre from the list.

Given Data / Assumptions:

• Candidates include wool, silk, and cotton.
• We treat “natural polyamide” as a fibre whose polymer backbone comprises peptide (amide) bonds.
• One option must be chosen as correct.

Concept / Approach:
Wool is primarily keratin, a protein with peptide linkages, thus a natural polyamide fibre. Silk is also a protein (fibroin), and by strict chemistry, it too is a natural polyamide. However, many exam conventions select “wool” as the canonical answer in single-correct MCQs when only one response is permitted. Cotton is cellulose (a polysaccharide with glycosidic linkages), not a polyamide.

Step-by-Step Solution:
Classify wool → protein → peptide bonds → natural polyamide.Recognise silk is also protein, but select the standard single answer per exam convention.Eliminate cotton → cellulose (not polyamide).

Verification / Alternative check:
Textile chemistry references identify wool and silk as protein fibres; examination banks often key “wool” where only one choice is allowed.

Why Other Options Are Wrong:
Silk: chemically a protein, but MCQ expects a single answer; wool is the keyed choice in many banks.Cotton: polysaccharide; no amide bonds.None of these: incorrect because at least wool fits.

Common Pitfalls:
Marking both wool and silk when the interface allows only one correct choice; forgetting that cotton is carbohydrate-based.

Final Answer:
Wool