Question

Which one is a protein fibre? (a) rayon (b) cotton (c) polyester (d) silk

Short answer

Silk is the protein fiber.

Step-by-step solution

Understand the Question

The question asks which option is a protein fiber. We need to identify which of the given materials is derived from a natural protein source.

Explore Each Option

Let's examine each option: (a) Rayon is a synthetic fiber made from regenerated cellulose; (b) Cotton is a natural fiber derived from the cotton plant, which is made of cellulose; (c) Polyester is a synthetic fiber made from petrochemical products; (d) Silk is a natural fiber produced by silkworms, and is made of protein.

Identify the Protein Fiber

Based on our exploration, we notice that silk, produced by silkworms, consists of proteins, specifically fibroin, and sericin, making it a protein fiber.

Key concepts

Natural Fibers

Natural fibers are materials that come from plants, animals, or minerals. These fibers have been used by humans for thousands of years because they are biodegradable and eco-friendly. There are two primary types of natural fibers: plant-based and animal-based.

• Plant-based fibers are often made of cellulose, a complex carbohydrate. Examples include cotton, linen, and jute.
• Animal-based fibers are typically protein-based, like wool and silk.

Natural fibers are appreciated for their comfort and breathability. They are widely used in clothing and textiles and are a sustainable choice compared to many synthetic alternatives.

Synthetic Fibers

Synthetic fibers are man-made fibers that are created through chemical processes. Unlike natural fibers, they are not derived from plants or animals but from petrochemicals.

• Common synthetic fibers include polyester, nylon, acrylic, and rayon.
• These fibers are designed to have specific properties, like strength, elasticity, and resistance to wrinkles and stains.

Synthetic fibers are popular because they can be mass-produced at a lower cost and with consistent quality. They also tend to be more durable than natural fibers. However, they are not biodegradable, which makes them less environmentally friendly.

Silk Production

Silk production is an intricate process involving the cultivation of silkworms. Silk is known for its luxurious feel and strength and has been highly valued for centuries. The process begins with the domestication of the silkworm, scientifically known as Bombyx mori.
Silkworms are fed mulberry leaves until they spin cocoons made of silk fibers. These cocoons are often collected and then boiled to soften the sericin that holds the fibers together. Once softened, the silk thread is carefully unwound from the cocoon.
This thread is then cleaned, spun, and woven into fabric. Despite being labor-intensive, silk production is a vital industry in many countries, contributing to both traditional and modern textile markets.

Fibroin and Sericin

Fibroin and sericin are two proteins found in silk. They play a crucial role in giving silk its unique properties.

• Fibroin is the primary protein that makes up the solid part of the silk fiber. It is responsible for the strength and durability of silk. This protein forms the core of the silk fiber, creating its smooth texture.
• Sericin is a gummy protein that holds fibroin fibers together within the silk cocoon. It helps protect the fibroin during the silkworm's cocooning process. However, it can be removed during silk processing to ensure a soft final product.

Both proteins contribute to silk's luxurious feel and are indispensable to its overall structural makeup. The presence of these proteins makes silk a natural protein fiber, distinguishing it from plant-based natural fibers like cotton.