From Molecules to Metabolism — V. When Chemistry Began to Regulate Its World

A boundary creates an inside.

But an inside is not yet enough.

For the chemistry within it to persist, what crosses the boundary must make a difference.

Some substances may be useful. Others may disrupt the reactions on which the system depends. Some gradients must be maintained; others must be dissipated. The boundary therefore becomes selective.

This changes the relation between system and environment.

The environment is no longer simply where the chemistry happens. The system participates in determining which parts of the environment can enter into its organisation.

And regulation need not begin with a regulator.

If a chemical pathway changes the permeability of a boundary, and that altered permeability changes the pathway's subsequent activity, chemistry has acquired a feedback relation. What happens inside can alter the conditions under which the inside continues to happen.

The system begins, in a minimal sense, to regulate its own circumstances.

This is different from merely reacting to the environment.

A reaction is changed by a condition.

A regulated system changes the conditions under which its own reactions occur.

That is another step toward metabolism: not simply a network of reactions, enclosed by a boundary, but a network whose activity helps determine the conditions of its own continuation.

The boundary is becoming selective.

The chemistry is becoming regulatory.

And the distinction between what happens to the system and what the system does about what happens is beginning to emerge.

Life may still be a long way off.

But chemistry has begun to acquire a world.