Oxygen. The Molecule that Made the World (Popular Science) by Nick Lane

Oxygen. The Molecule that Made the World (Popular Science) by Nick Lane

Author:Nick Lane [Lane, Nick]
Language: eng
Format: epub
Tags: 9780198607830
ISBN: 0198607830
Published: 0101-01-01T00:00:00+00:00

C H A P T E R T E N

The Antioxidant Machine

A Hundred and One Ways of Living with Oxygen

Governments work with tight definitions of words like

‘unemployed’, ‘literacy’, or ‘no more taxes!’. Opposition spokes-men and newspaper editors dispute the validity of their definitions. Words fly back and forth, all sound and fury, signifying little.

Scientists are considered to be above this kind of thing. The terminology of science brooks no opposition: it is clearly defined and quantifiable, albeit unreadable. Scientists strive to render a definition into a mathematical symbol. Only when the term sits comfortably in an equation are we happy. Yet even within the perfect discipline of mathematics, precision is not always possible. The ‘fiddle factor’ is an ever-present bogey, which symbolizes the resistance of the world to petty classification.

In biology, the trouble with definitions is far worse than in mathematics. Few biologists ever use the word ‘proof’ — it is far too exact. Doctors rarely use the word ‘cure’. Who knows, after all? Remission is a more comfortable word, if only because it means very little: “the illness seems to have gone away for now, for all I can see; I have no idea if it will come back”. Nature deftly sidesteps our clumsy swings at a definition. How does one define ‘life?’ Reproduction and some form of metabolism seem to be musts, but then is a virus alive? It has no metabolism of its own and so falls outside most definitions of life. If you can define life to encompass a virus, then how about the infectious prion, which is simply a protein?

A Hundred and One Ways of Living with Oxygen • 195

How does one define ageing? A relentless decline in faculties ending in death? Or was that just a description? If we can’t define life, what on earth is death? If a prion is not alive, is it dead? If so, does that mean we can’t kill it?

I’ve no intention of wallowing in this sea of semantics. Of course there are answers, albeit rarely simple. My concern now is to find a wider definition of the term ‘antioxidant’. We saw the potential for confusion in Chapter 9. The problem is one of precision: just how precise can we be in defining such a slippery concept?

The original definition of ‘antioxidant’ came from chemistry. As befits a science full of symbols, it had a precise meaning. An antioxidant is an electron donor that prevents a substance from being oxidized (or stripped of electrons). The word came of age in food technology in the 1940s. Fatty foods, such as butter, go rancid if left in the air. Technically, they ‘peroxidize’. Peroxidation is a chain reaction started by oxygen free radicals, such as hydroxyl radicals, which attack lipids to get an electron.

They may seize an electron and run, or become mired in the lipid like a rugby player who got the ball but couldn’t escape the scrum. Either way, the lipid loses an electron: it has become a free radical and so attacks its neighbours to get an electron back.



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