Chemistry Reference
In-Depth Information
gen, associated with type II, also makes up cartilage. The differences
between the different types resides in the way the amino acid molecules
are linked to each other within the polypeptide chains that make up the
basic structure of collagen.
When collagen is heated, it is
denaturated
, losing its structure: the
polypeptide chains separate and unwind, and, as the collagen cools down,
it soaks up surrounding water and forms
gelatin
.
11.1.
ANIMAL SKIN
The
skin
is is the outermost protective covering layer of the body of animals;
in humans, the skin represents under 15% of their body weight; and, in
adults, ranges in area within one and two two square meters. It is a tough
but flexible membrane that surrounds the body and fulfills many physio-
logical functions: it bounds the size and shape of animals, protects their
bodies, regulates their temperature, and prevents the loss of water and the
invasion of foreign microorganisms and viruses. All these functions are pos-
sible because of the particular composition and structure of the skin, which
is quite similar for all vertebrates: it is made up of intertwined bundles of
fibers of collagen—the main component of all skin—water, and lesser
amounts of fats, nucleic acids, and coloring matter (see Table 83) (Woodhead-
Galloway 1980).
The skin of mammals, including humans, consists of three layers (see
Fig. 72):
TABLE 83 Approximate Composition of Animal
(Mammal) Skin
Component
Percent
Protein
32
Collagen
29
Keratin
2
Albumin
1
Fat
2
DNA
below 1
Pigments
about 0.5
Mineral salts
about 0.5
Water
65
