Geology Reference
In-Depth Information
So passionate is oxygen in its quest for electrons that once inside the cell its reactions
give rise to highly toxic free radicals that can interfere with DNA, causing ageing and
even cancer. Free radicals are atoms that end up with a missing electron when the weak
bonds that they have been involved in break up, especially after they have experienced
the ardent attentions of oxygen. The free radicals then feel impelled to capture electrons
from neighbouring molecules, thereby creating new free radicals that oftentimes set off
a potentially highly damaging cascade effect. Cells have invented a host of enzymes to
mop up the rogue chemical beings, but a small number evade capture to carry out the
demolition of the genetic material—a process that will eventually kill most of us. So,
like all the nutrients that are essential for life and even solar energy itself, oxygen is both
a life-giver and a dealer of death.
Phosphorus as a lone element is never encountered in nature. It was first collected in
its pure form by Henning Brandt in 1669 from urine, perhaps his own, which he evap-
orated to leave a residue that he heated until red-hot. He collected and condensed the
resulting vapour, ending up with a white powder that glowed in the dark and spontan-
eously burst into flame when exposed to the air. These properties give phosphorus its
name, from the Greek words
phos
(light) and
phorus
(bearing); hence it is the 'light-
bearer' of the chemical world. In living beings, phosphorus is involved in light-bearing
in more subtle ways: firstly through its central involvement in the storage and release
of energy, ultimately derived from the sun, that powers the light of sentience in life it-
self; and secondly as the ultimate source of the eerie light of bioluminescence so much
favoured by some planktonic algae and by creatures of the ocean deeps. Some speak of
phosphorus as Gaia's 'master nutrient' because of its scarcity (it is the eleventh most
abundant element in the Earth's crust) and because of the difficulty of returning it from
the marine sediments, where it is relatively abundant, to the land and to the surface of
the ocean, where it is scarce; this feat is made especially difficult because there is no
gaseous molecule in wild nature that acts as the agent for this transfer.
Phosphorus has its two inner orbits nicely replete with electrons, but its outer orbit,
the third one out, misses three. Phosphorus links with carbon and nitrogen to make the
ATP molecule, which is the front-line energy acceptor molecule present in every living
being, whether microbe or elephant. We humans process an astonishing one kilogram
of ATP per hour, every day of our lives. It is also found in the DNA molecule, and in
vertebrates occurs most commonly in bone, linked to calcium and oxygen atoms as cal-
cium phosphate. Like oxygen, phosphorus is a passionate chemical being. When the two
naked elements encountered each other in the air, the flames that shocked Brandt bore
witness to their ardent and explosive attraction to each other. The result of their fiery
affair is the phosphate ion, in which phosphorus is linked to four oxygen atoms.
