One of the perennial stories that keeps appearing
in "Believe-it-or-Not" columns and newspaper fillers is
that all of the elements in the human body are worth only $1.25,
$1.98, or $3.50, depending on the current state of the chemical
market. This is an old cliché, which misses the essential
point that makes diamonds more valuable than charcoal. In any collection
of atoms, it is the arrangement of atoms that is as important,
or more important, than the atoms themselves. The arrangement of
iron and carbon atoms in the heme group in a protein, shown on the
right, bears little resemblance to iron carbide, an inorganic compound
that contains the same elements.
Another frequently heard generalization is that a mammal is 65%
water, and that this water is a dilute salt solution resembling
sea water. In this view, a mammal is a walking bit of oceanic environment.
This attitude is less of a cliché because it has a grain
of truth in it. As we shall see in Chapter 26, the truth in this
theory comes from the way in which life originally evolved in the
oceans. Again, however, to say that a living creature is "only
enclosed sea water" is to overlook the crucial importance of
the nature of the enclosure.
view of the heme group, shown in side view on the following
page. A similar heme group is found in the oxygen-carrying protein
hemoglobin. Copyright © 1969 Dickerson and Geis; from R. E.
Dickerson and I. Geis, The Structure and Action of Proteins,
W. A. Benjamin, Inc.