Unit 2 - Lecture 8 Topic 1

Question 1

Natural Protein Fibres:

Answer 1

Fibres that are of animal origin. Mainly mammals, like wool and other animal hair fibres, but also from insects and spiders, like silk. Protein molecules are the building blocks for all textile materials of animal origin. Protein fibres will react to solvents, chemicals and biological attack in a similar way.

Question 2

Explain the molecular make-up of protein fibres:

Answer 2

Protein fibres are built up of amino acids linked together in long chains. These amino acids contain basic amino groups of NH2 and acidic carboxylic groups of COOH linked together by peptide linkages. The reason protein materials differ in characteristics is due to the amino acid side groups.

Question 3

How do alkali’s effect protein fibres?

Answer 3

Neutral or only slightly alkaline soaps and detergents can be used on protein fibres. Perspiration weakens these fibres.

Question 4

Polypeptide:

Answer 4

Many peptide bonds, ie. natural protein fibres.

Question 5

What are the possible acidic, basic, polar, non-reactive, disulphide bonds and sulphur containing side groups involved in amino acid side-groups of natural protein fibres?

Answer 5

Acidic: Glutamic accident (COOH)
Basic: Lysine (NH2)
Polar: Serine and tyrosine (OH and benzene+OH)
Not reactive: Glycine and Phenylalanine (H and benzene)
Contain sulphur: Cysteine (SH)
Disulphide bonds: Cystine (S+S)

Question 6

What are the possible acidic, basic, polar, non-reactive, disulphide bonds and sulphur containing side groups involved in amino acid side-groups of natural protein fibres?

Answer 6

Acidic: Glutamic accident (COOH)
Basic: Lysine (NH2)
Polar: Serine and tyrosine (OH and benzene+OH)
Not reactive: Glycine and Phenylalanine (H and benzene)
Contain sulphur: Cysteine (SH)
Disulphide bonds: Cystine (S+S)

Question 7

Amino acid side-groups of disulphide bonds:

Answer 7

These are important in wool but not present in silk. They provide resiliency, stability, and strength to wool fibres.