Silkworm: Life Cycle, Silk Chemistry, and Applications

Silkworm is essential in chemistry and helps students understand various practical and theoretical applications related to this topic. Silkworm rearing and silk production show how biology and chemistry come together to create useful materials, especially natural fibres like silk.

What is Silkworm in Chemistry?

A silkworm refers to the larva of the Bombyx mori moth, which is reared especially for silk production. In chemistry, silkworms are important because they show the natural production of fibre (silk), protein chemistry (fibroin and sericin), and green alternatives to synthetic materials. 

This topic links closely to sericulture, natural fibres, and applied industrial chemistry, making it a key chapter in your curriculum.

Molecular Formula and Composition

Silk fibre from the silkworm is mainly a protein called fibroin, with the approximate chemical formula (C₁₅H₂₃N₅O₆)_n. Silk also contains a gummy protein called sericin. Both are biopolymers and fall under the class of natural animal proteins. The strength, shine, and flexibility of silk come from the arrangement of these protein molecules.

Preparation and Synthesis Methods

The preparation of silk involves a combination of biological and chemical processes:

1. Silkworm eggs are laid and hatch into larvae, which feed mainly on mulberry leaves.
   
   As the larvae grow, they spin a cocoon using silk, secreting it from special glands near their mouth.
   
   
2. To extract silk, the cocoons are collected and boiled. This softens the sericin, allowing the long fibroin filaments to be unwound and spun into silk thread.
   
   Eco-friendly or "Ahimsa" silk makes it possible to obtain silk without killing the pupa, by letting the moth emerge naturally before reeling.
   
   

Physical Properties of Silk Fibre

• Silk fibre made by silkworms is strong, light, and lustrous. It feels smooth and can be stretched up to 20% of its original length before breaking. 
• Its melting point is around 170°C, and it dissolves in concentrated acids but resists weak acids. 
• Silk is also soft to touch and comfortable next to the skin, making it a favourite for luxury clothing.

Silkworm Life Cycle

Understanding the life cycle is important as it links biology and chemistry. The stages include:

1. Egg: Laid by adult female moths, hatch within 10 days.
   
2. Larva (Caterpillar): Eats mulberry leaves and grows; moults 4 times in around 25 days.
   
3. Cocoon: Forms cocoon around its body, spinning silk fibre. Each cocoon can contain up to 1 km of silk thread.
   
4. Pupa: Caterpillar changes inside the cocoon.
   
5. Adult Moth: Emerges from cocoon, mates, and lays new eggs. Life cycle repeats.
   

Chemical Properties and Reactions

Silk fibre from silkworm has key chemical properties:

• It consists of fibroin (structural protein) and sericin (sticky protein).
• Fibroin is mostly made up of amino acids glycine and alanine, arranged in β-sheet structure, making it very strong and shiny.
• Silk is hydrolyzed by strong acids or alkalis and is easily dyed due to reactive amino acid groups.
• It is biodegradable and can be broken down by natural enzymes.

Frequent Related Errors

• Thinking all silkworms are used for silk—only Bombyx mori is mainly used in sericulture.
• Assuming silk extraction is purely a mechanical process without any chemistry involved.
• Mixing up "silk" with synthetic fibres or assuming silk is plant-based.
• Confusing "sericin" and "fibroin" roles in silk composition.

Uses of Silkworm in Real Life

Silkworms and their silk have many important uses, both traditional and modern:

• Natural silk fibre for luxury clothing and textiles
• Biodegradable surgical sutures in the medical field
• Raw material in biotechnology and tissue engineering
• Edible insect in some cultures (silkworm pupae)
• Source for inspiration in designing strong biopolymer materials

Relation with Other Chemistry Concepts

Silkworms and silk link closely with natural fibres, protein chemistry, and green chemistry topics. The study of silkworms also connects to environmental chemistry thanks to silk’s biodegradability and eco-friendly reputation.

Step-by-Step Reaction Example

Let’s see one of the common chemical extraction steps in silk processing:

1. Silkworm cocoon is boiled in water.

2. Hot water helps dissolve sericin (gum protein) and softens the cocoon.

3. The fibroin (main silk fibre) is carefully unwound using a spinning reeler.

4. The silk threads are dried, twisted, and woven into cloth.

Lab or Experimental Tips

Silkworm silk can be identified using a flame test: it burns slowly and smells like burning hair (since it’s protein). Silk dissolves in concentrated hydrochloric acid but not in water. In Vedantu’s live sessions, educators highlight such tips to make learning chemistry easy and fun!

Try This Yourself

• Name the two main proteins found in silkworm silk.
• Draw and label the stages of the silkworm life cycle.
• Compare silk to synthetic fibres—list two differences in their chemistry.

Final Wrap-Up

We explored silkworm—its biology, role in chemistry, life cycle, silk production, and the amazing role it plays in real life. Silkworm and silk chemistry blend science and tradition, making the topic interesting for students and important for society. For more deeper learning and live interactive classes, explore chemistry resources at Vedantu.

Related Topics: Natural Fibres, Green Chemistry