Seen through a microscope there is an appearance of almost frantic activity. On a deeper level it is known that molecules are being synthesized at an enormous rate. Almost any enzyme catalyzes the synthesis of more than 100 other molecules per second. In ten minutes, a sizeable fraction of total mass of a metabolizing bacterial cell has been synthesized. Each of those 100 trillion cells functions like a walled city.
Power plants generate the cell's energy.
Factories produce proteins, vital units of chemical commerce. Complex transportation systems guide specific chemicals from point to point within the cell and beyond. Sentries at the barricades control the export and import markets, and monitor the outside world for signs of danger. Disciplined biological armies stand ready to grapple with invaders. All life . .