UPPSC 2020 Prelims GS Paper-I · Question 109 of 150

Correct — A, Fibroin. Fibroin is a natural fibrous protein — the structural core of silk secreted by silkworms (and spiders) — so it is not man-made. The other three are all synthetic polymers: Lexan (polycarbonate), Neoprene (polychloroprene rubber) and Teflon (PTFE) are industrially manufactured. Hence the non-synthetic substance is fibroin.

• (b)Lexan — Lexan is a trade name for polycarbonate, a synthetic thermoplastic used in shatter-resistant sheets and lenses — man-made, not natural.
• (c)Neoprene — Neoprene is polychloroprene, a synthetic rubber (the first commercial synthetic rubber, 1930s), used in wetsuits and gaskets.
• (d)Teflon — Teflon is polytetrafluoroethylene (PTFE), a synthetic fluoropolymer used as a non-stick coating.

Polymers are either natural — made by living organisms, such as silk fibroin, cellulose, wool and natural rubber — or synthetic, i.e. manufactured, such as nylon, PTFE, polycarbonate and neoprene. Fibroin is a natural animal protein fibre, whereas Lexan (polycarbonate), Neoprene (polychloroprene) and Teflon (PTFE) are all industrially synthesised.

The question hides one natural biopolymer among three brand-name plastics. If you recognise fibroin as the protein of silk, it is clearly the natural one; the trick is that the other three use trade names (Lexan, Teflon, Neoprene) that may be unfamiliar but are all synthetic.

• Fibroin — natural protein fibre of silk (from silkworms/spiders)
• Lexan — polycarbonate, a synthetic thermoplastic
• Neoprene — polychloroprene, a synthetic rubber
• Teflon — PTFE, a synthetic non-stick fluoropolymer

• Being thrown by an unfamiliar trade name (Lexan) and guessing it is natural
• Forgetting that silk/fibroin is a protein made by an organism, hence natural

'Which is NOT synthetic' / odd-one-out items pair one natural biopolymer with several brand-name plastics — identify the biological material.

No directly related past PYQ was found.

• practice — not a real PYQ

  Fibroin is the principal protein of which natural fibre?

  • (a)Cotton
  • (b)Wool
  • (c)Silk
  • (d)Jute

  Answer(c) Silk — fibroin forms the core filament of silk.

• practice — not a real PYQ

  Which one of the following is a synthetic rubber?

  • (a)Latex
  • (b)Neoprene
  • (c)Gutta-percha
  • (d)Fibroin

  Answer(b) Neoprene — polychloroprene, the first commercial synthetic rubber (latex and gutta-percha are natural).