Page 88 - The Miracle in the Atom

FURYLMETHANETHIOL
This molecule is one of those
responsible for the aroma of
coffee. The stimulating action
of coffee is due to caffeine.
The colour of roasted coffee
beans seen left is largely due
to the browning reaction that
occurs when organic sub-
stances containing nitrogen
are heated. Temporarily
trapped within the beans are
the molecules responsible for
flavour and stimulation. 35

b-KERATIN
Silk, the common name of b-Keratin, is the
solidified fluid excreted by a number of insects
and spiders, the most valuable being the exu-
dent of the silkworm, the caterpillar of the silk
moth. It is a polypeptide made largely from
glycine, alanine, and smaller amounts of other
amino acids. b-Keratin molecules do not form a
helix; instead they lie on top of each other to
give ridged sheets of linked amino acids, with
glycine appearing on only one side of the
sheets. The sheets then stack one on top of the
other. This planar structure is felt when you
touch the smooth surface of silk. 36