Soundings: Air pollution self-defense

No sooner had life evolved on this planet than it faced a problem: Keeping itself alive.

It was a cell-eat-cell jungle out there. Even "the only living thing on Earth" would have been hard-pressed to keep itself alive: To keep itself warm (but not too warm), moist (mineral-rich water, please, not bland rainwater) and unradiated (raw sunlight can break apart biological molecules).

But it could have been worse. There was, fortunately, no free (pure, uncombined) oxygen in the oceans or atmosphere.

Rubbing a balloon transfers negatively-charged electrons from your clothes to the balloon. Bearing an electric charge, the balloon becomes attractive to anything not-so-charged, such as a wall.

By sharing and transferring electrons, atoms become charged, attract each other, and bond to form molecules: Water, proteins, fats, carbohydrates.

Oxygen atoms are gluttons for electrons, scarfing up electrons, oxygen destroys the bonds that hold atoms together. Iron rusts, fats rancidify, fires burn.

Grabbing electrons, by oxygen or any other atom, is called oxidation.

Half-a-billion or a billion years after life evolved, microbes learned to harness sunlight to make food by re-arranging the atoms in carbon dioxide, and bonding hydrogens to those atoms. The hydrogen atoms are obtained, most often, by splitting them off molecules of water.

Water is composed of both hydrogen and oxygen atoms.

Removing the hydrogens, photosynthesizers release the (useless) oxygen into the environment.

If they're to bond, atoms must approach each other closely. Should its internal milieu become too dilute, close approaches become rare, and life slows down ... too slow, and the organism dies. Cells must keep their internal contents sufficiently concentrated to keep their chemistry going.

If its internal milieu should become contaminated with atoms or molecules that interfere with its chemistry - should toxins enter the cell - life would again slow and, again, perhaps die. Cells must keep their internal contents uncontaminated.

To keep what's supposed to be inside in, and to keep what's outside out, living things construct membranes (the inside of your cheek is a patchwork of membranes).

The molecules with which we construct those membranes are especially susceptible to oxidation - to having their electrons stolen, to being ripped apart.

Only a few substance are better oxidizers than oxygen.

One of these is ozone.

Once photosynthesizers began filling the environment with oxygen, evolution kicked into self-defense mode.

Living things (including the photosynthesizers themselves) responded by evolving chemicals that would sacrifice themselves to the oxidizers - easy targets that would be oxidized before precious cellular molecules were destroyed.

One of these protective chemicals - antioxidants - is ascorbate: vitamin C.

Most organisms can manufacture vitamin C for themselves. Sometime in the past, however, a mutation spread through a population of organisms, knocking out their ability to make the vitamin. From that time on, members of this group - the primates (that's us) - have had to rely on their diet to obtain vitamin C.

Membranes are part fat, part water-soluble protein.

Vitamin C dissolves in water; it can't get to the fatty parts of our bodies, such as membranes. But other antioxidant vitamins - E, for instance - are fat soluble.

Research suggests that antioxidants, such as vitamins C and E, can prevent some, if not all, of the symptoms of ozone exposure.

Before pigging out on vitamins, however, realize that many of them play multiple roles in the body - consuming too much can have "side-effects."

Researchers expecting the anti-oxidant beta carotene to protect smokers from lung cancer found it to have the opposite effect. Similarly, research suggests it's possible to consume too much vitamin E.

Moderation seems wise. So does getting the bad stuff out of our air.