Question

Natural silk is a (a) polychloroprene (b) polypeptide (c) polyacrylonitrile (d) polysaccharide

Short answer

Natural silk is a polypeptide (b).

Step-by-step solution

Understand the Question

We need to identify the correct classification of natural silk from the given options based on its chemical composition.

Identify the Composition of Silk

Natural silk is primarily composed of proteins, which are long chains of amino acids. Specifically, silk is made up of a protein known as fibroin.

Define Polypeptides

A polypeptide is a polymer consisting of a chain of amino acids linked together by peptide bonds. Since silk is made of fibroin, a protein formed by amino acids, it is classified as a polypeptide.

Rule Out Incorrect Options

- Polychloroprene is a type of synthetic rubber, not related to silk. - Polyacrylonitrile is a synthetic polymer used in textiles but not in silk. - Polysaccharide is a carbohydrate polymer, while silk is a protein-based fiber.

Select the Correct Option

Based on the chemical structure and the composition of natural silk being a type of protein, we select 'polypeptide' as the correct classification.

Key concepts

Understanding Polypeptides

Polypeptides are fascinating molecules that play a critical role in biology and chemistry. Often regarded as the building blocks of proteins, they are chains of amino acids linked together by peptide bonds.
These chains vary in length and sequence, which influences their ultimate structure and function.
They form when amino acids undergo a dehydration synthesis reaction, resulting in the formation of a peptide bond and the release of a water molecule. When you think of proteins, consider them as large, complex structures composed of one or more polypeptide chains folded and arranged in specific ways.
This folding is essential, as it determines the protein's function within biological systems.
Natural silk, for instance, is mainly composed of the protein fibroin, a type of polypeptide that gives silk its strength and elasticity. Polypeptides and proteins serve many functions in organisms:

• They act as enzymes, facilitating biochemical reactions.
• They play a structural role, as seen in muscle fibers and silk threads.
• Transport, signaling, and immune defense are also crucial functions.

Chemical Composition of Silk

Silk is a remarkable natural material known for its lustrous appearance and impressive strength.
IIt primarily derives from the protein called fibroin, revealing silk's underlying complexity.
This protein is what makes silk lightweight yet resilient, allowing it to be both delicate and durable. The chemical composition of silk involves fibroin, which is a long chain of polypeptides.
This chain consists of recurring sequences of specific amino acids like glycine, alanine, and serine.
These amino acids aid in forming the hydrogen bonds that give silk its unique properties, such as its shiny appearance and high tensile strength. A special silk feature is its biocompatibility, making it popular in medical applications:

• It serves in sutures, providing comfort and reliability in tissue repair.
• The material is explored in developing biodegradable implants.
• Scientists are also researching its use in drug delivery systems.

Amino Acids in Proteins

Amino acids are fundamental to all proteins, including those forming natural silk.
They are organic compounds that combine to form proteins, which are essential for life.
Twenty different amino acids can create a wide variety of proteins, each with its specific role and properties. Each amino acid has a central carbon atom, hydrogen atom, an amino group (NH₃⁺), a carboxyl group (COO⁻), and a unique side chain known as an R group.
It is these R groups that determine the chemical nature of each amino acid, influencing how proteins fold and function. In silk, the primary amino acids are glycine, alanine, and serine.
Glycine is a small amino acid, allowing tight packing of the strands and forming strong fibers.
Alanine and serine contribute to the silk's fine texture and durability by interacting with each other and forming hydrogen bonds. Amino acids also have essential functions beyond silk production:

• They assist in cellular repair and enzyme production.
• Synthesize hormones and neurotransmitters critical for body functions.
• Provide an energy source during metabolic processes.