Chemically silk fibres are predominantly

Chemically, silk fibres are predominantly composed of proteins. Silk is a natural protein-based fiber secreted by silkworms to form their cocoons [t1, t5]. It primarily consists of two specific proteins: fibroin and sericin [c1, t8]. Fibroin, a fibrous protein, constitutes approximately 70-80% of the fiber and forms the structural core, providing tensile strength and rigidity [t1, t3]. Sericin is a gelatinous or globular protein that acts as a gum to cement the fibroin filaments together, making up the remaining 20-30% [c1, t2]. While silk may contain trace amounts of waxes, carbohydrates, and minerals (totaling about 3%), its fundamental chemical nature is that of a nitrogen-containing polymer made of alpha-amino acids [t2, t4]. This distinguishes it from plant-based fibers like cotton, which are carbohydrate-based (cellulose) [t5].

Sources

1. [1] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 9: Agriculture > Production > p. 95
2. [2] https://www.sciencedirect.com/topics/engineering/silk-fibre