What
chemical process does your hair and your cars' tyres have in
common ?
Hair fiber is made from proteins called keratins
and proteins are chains of amino acids. Different types of
protein contain different amino acids, linked together in a different
order. Keratin happens to contain lots of the amino acid cysteine,
which is special because it contains a sulfur atom. The sulfur
atoms from two cysteines can join together, forming a disulfide
bond. The keratin in your hair has lots of disulfide bonds - both
within a single protein chain, and between protein chains - and
these bonds strengthen your hair. Disulfide bonds make other materials
stronger too. In the 1800's, Charles Goodyear discovered the process
of rubber vulcanization. This involves heating up rubber with
sulfur. The sulfur crosslinks the rubber molecules with disulfide
bonds, making the rubber stronger. Essentially this is the same
process that occurs to give hair its strength.
How
is keratin used as a method of drug delivery ?
Keratin is sometimes used to coat pills. The keratin
coating will remain intact in the stomach, which is acidic, but
dissolves in the intestine, which is basic (the intestine secretes
base
to neutralize stomach acid, so your intestine does not
get digested!). Coating pills with keratin allows drug companies
to ensure that a medicine is directly delivered to your intestine,
where it can be absorbed into your bloodstream, and avoids being
damaged by the acids in the stomach.
Can
you eat your hair ?
The answer
is both yes and no. Some people develop a habit of plucking and
eating their hair. It
is
a condition called "trichophagia". This is
potentially a very dangerous condition because your
stomach, which is acidic, cannot break down the hair fiber. The hair fiber is quite
irritating to the stomach and can cause ulcers. In some
cases the eaten hair can collect into a hair ball and build up into a sizeable
mass. This can be very dangerous, even life threatening
because it irritates
the stomach to much. In these cases the only treatment
is an operation to remove the hair ball. However, hair
fiber is made from keratin
and hair keratin is mostly made from the amino acid
cysteine. Cysteine is a food additive - particularly
used in making pizza bases. One of the food industry's sources of the amino
acid cysteine is hair. Hair, mostly collected in China,
is the raw material from which cysteine is extracted.
Who
has more hair follicles - a mouse, a horse or a human ?
The answer is they all have about the same number of hair follicles.
Although people generally think of humans as only having hair
on the scalp and some on the body, almost all our skin is covered
in hair follicles with the exception of the palms and soles. We
have little follicles, called vellus hair follicles, over our
face
and our
bodies, that
only
produce
tiny,
non-pigmented hair fibers. Because they are not so easy to see,
we tend to forget about them, but they are still hair follicles.
A horse doesn't have many more hair follicles than a human - it
is just
that the hair follicles are bigger and spread further apart in
the skin. At the other end of the scale, mice have also have about
the same number of hair follicles, but the follicles are much
smaller and closer together in the skin. In total, a human has
about 5 million hair follicles. Of those one million are on the
head and of these around 100,000 actually cover the scalp area.
A human hair fiber on the scalp is typically around 80 micrometers
thick. a horse hair fiber is typically 120 micrometers thick (though
it varies in different strains of horse) while a mouse hair fiber
is typically around 5 micrometers thick. |
