Page 10 - Curriculum Visions Dynamic Book

Amino acid Amino acid
In the simplest amino acid the shaded box would be a hydrogen atom.This section of the molecule is different for different amino acids.
Natural polymers
A section of protein chain
Water
There are two kinds of polymers that
make up natural fibres. They are called
animal proteins (in which amino acids are joined
by chemicals called amides) and plant carbohydrates (in process. which chains of simple sugar molecules add together).
Proteins and carbohydrates are formed in different
(Above) A natural animal ways. All animal silk, hair, or wool is pushed out, or fibre or filament is made
extruded, from special places on the skin or special organs.
Although proteins are extruded as filaments, hair often falls
out when it has reached a certain length, and then a new a fibre such as a hair,
filament begins to grow again. That is why hair (including wool) is usually put in the category of fibre.
the animal cell builds proteins using amino acids. Each time this reaction
cellulose is the building block of plant cells. takes place, water is
artificial fibres that also formed by condensation polymerisation (see pages
The cells overlap. They have a definite length and are
not produced in filaments. As a plant stem grows, for
example, it produces new fibres, rather than extending and polyester are two
the existing ones.
The forces holding the molecules together are very
strong and hard to break (see the manufacture of rayon on 14 and 42). pages 12 and 39). Natural polymers usually have melting
points that are so high that they decompose, or char, before
they melt. This makes them very difficult to work with or
to re-form into fibres with different properties.
Of the natural fibres, those with long chains and few
branches are the most useful for making into fabrics. Thus cellulose is a useful fibre-former because its molecules lie in long chains with few branches. By contrast, starches, which
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of proteins. The building blocks of proteins are amino acids. To make
produced. This is a process called condensation polymerisation. Nylon
Water is a product of this condensation polymerisation