Chemistry Reference
In-Depth Information
Chapter 19
Biomineralisation
“For the harmony of the world is made manifest in Form and Number, and the heart and soul and all poetry of Natural
Philosophy are embodied in the concept of mathematical beauty.”
1
Introduction
359
Principles of Solid-State Biological Inorganic Chemistry
360
An Overview of the Major Classes of Biominerals
361
INTRODUCTION
When we survey the living world around us we can only wonder at the diversity of its shapes and forms. The
Scottish polymath,
2
D'Arcy Thompson addressed this subject in his classic book On Growth and Form, first
published in 1917, and in a revised edition in 1942 (the latter, a mere 1116 pages long) (
Thompson, 1942
)
. The
central thesis of his book was that biologists placed too much emphasis on the role of evolution, and not enough on
the roles of physical laws and mechanics, as determinants of the form and structure of living organisms. He
decided that the laws concerned with static and dynamic forces of tension, compression and shear occurred in all
living structures and influenced both growth, function and form. The bones of a skeleton in a museum would be
a limp heap on the floor without the clamps and rods that pull them together, and Thompson argued that in living
animals, tension plays as important role in holding the skeleton together as does weight. In the same way, tension
holds together the arches of medieval cathedrals, and steel cables provide the tensile strength on which suspension
bridges are hung.
We now recognise that, while much of biology relies on inorganic structures, biominerals, to supply the tensile
strength and the other material properties that we associate with, for example, bone, the diversity of form and
shape depends on the organic matrix in which the biomineral is allowed to form. It is a little like the construction
of buildings with reinforced concrete
e
the mould determines in what shape and form the concrete will set. And it
is just so in biomineralisation
the organic mould is the organic matrix in which the process of selective
precipitation of the inorganic mineral to be formed is directed, indeed, one might even say orchestrated, by the
organic component.
Calcium is probably the most widely distributed element in biominerals, particularly in the “hard parts” of
organisms, like teeth and bones. With the recognition that numerous minerals based on a great number of cations
(among which figure Ba, Ca, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, and Zn) as hydroxides, oxides, sulfides, sulfates,
carbonates, and phosphates,
e
the more restrictive term 'calcification' has given way to the more global
'biomineralisation'.
1. D'Arcy Wentworth Thompson « On Growth and Form » (1917).
2. Thompson was offered the chair of Classics, Mathematics, or Zoology at the University of Saint Andrews
e
he chose the latter.
