It’s the saga of the molecule that saved the world |

It’s the saga of the molecule that saved the world

The earliest beings to live on Earth were barely alive. They were complex molecules, clusters of atoms, their assembly powered by lightning or cosmic rays or the gentle warmth of oceanic hot springs. Atoms linked up, broke apart and linked up again. Some eventually attained the ability to grow and reproduce – to live.

It takes energy to keep oneself alive. Everything alive must eat to live.

Food, to a first approximation, can be thought of as a spring toy that pops open when you release the catch. The spring stores energy when you squeeze it down; release the catch and the spring expands, releasing the energy you squeezed into it – energy that can be captured and put to use.

Our early ancestors were surrounded by nonliving molecules that had also been assembled with (and now stored, like squeezed-down springs) the energy of the electricity or radioactivity or heat around them. Full of energy, these molecules were food. Our ancestors lived in their own dinner bowl, an ocean of soup.

The early life forms were fruitful, and multiplied. They evolved into cells, able to eat ever more types of molecules (and each other).

Populations soared.

The history of life is a history of crises. The crisis may come from the Earth, say, as massive volcanic eruptions; from the sky, say, as an asteroid augering in; or from the actions of life itself.

As microbial populations grew, so did their collective appetite. It wasn’t long – some millions of years – before they faced a major crisis: The soup was growing thin.

Really thin soup is nothing but water, and early life had plenty of that. But the water molecule is like a spring toy that’s already expanded – there’s no way to get energy from it.

Briskly brush a plastic pen through your hair a few times, and then pass it over a piece of paper confetti. The confetti is electrically neutral, but the pen has ripped electrons off your hair, and now carries a negative charge. Feeling the negative charge of the pen, electrons in the confetti move through the paper as the pen comes close, leaving the paper positively charged on the side closest to the pen. Opposites attract, so the confetti jumps toward the pen.

Certain atoms, or clusters of atoms, have a great affinity for electrons. Oxygen, for instance, scarfs up electrons like mad (think fire). It’s by sharing electrons that the atoms in molecules hold together; losing their electrons, molecules fall apart.

The work of life involves putting molecules together and taking them apart. We do this work with tiny machines – other molecules that we assemble in our cells.

For millions of years before the “thin soup crisis,” early cells had been experimenting with such molecular machines. One of these machines evolved into a molecule even better than oxygen at grabbing electrons off other molecules … when it’s energized by light. This new molecule could even wrest electrons off a molecule of water (H2O – two atoms of hydrogen bonded to an atom of oxygen).

Deprived of electrons, the water molecule falls apart. The oxygen atoms escape, but the hydrogens are quickly bonded to molecules of carbon dioxide to form a molecule of sugar.

No longer did these early cells have to eat soup.

Some 4 billion years later, as the weather warms and the days grow longer, the manufacture of chlorophyll (“leaf green”) – the most abundant molecule on the surface of the Earth – has shifted into high gear, and the world around us is greening up.

Trained as a biologist, Alan Stahler is also an amateur astronomer. He teaches biology and geology at Bitney Springs Charter High School. His science programs can be heard at noon on alternate Tuesdays on KVMR-FM (89.5).

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