Shown here are human skin cells. The two dark pink layers at the top make up the epidermis, the tentacles reaching into the light pink dermis.

Jack Challoner

Understanding the structure and functioning of cells involves a problem that has become characteristic of all modern biology.

The organization of a cell has often been compared to that of a factory, where different parts are manufactured at different sites, stored in intermediate facilities, and transported to assembly plants to be combined into finished products, which are either used by the cell itself or exported to other cells.

Cell biology has made enormous progress in understanding the structures and functions of many of the cell’s subunits, but it still has revealed very little about the coordinating activities that integrate those operations into the functioning of the cell as a whole.

Fritjof Capra & Pier Luigi Luisi, Systems View Of Life

Different cities are similar in that they all have roads, but the actual road map differs from town to town. That’s partly true of cells too, but surprisingly it seems that all cells share the same basic road plan, at least for the city center itself.

Genes change and evolve, but metabolic pathways remain essentially unchanged. As poet Edna St. Vincent Millay wrote, “Life isn’t one damn thing after another, it’s the same damn thing over and over.”

A bacterial cell living deep down in the crust of Earth makes its letters for DNA through the same succession of steps that you do, even if many of its genes have diverged almost beyond recognition. Genes are far more malleable than metabolism.

The reason that city street-plans differ but the central metabolic maps of cells do not is quite simple: cells descend from a common ancestor, but cities do not.

Core metabolism has changed little in part because it was never powered down in its four-billion year history.

Nick Lane, Transformer

Human beings, whatever their age, are completed forms of what they are, just as societies are completed forms of what they are.

Growing is becoming different, not better or faster.

You may become better or faster or more fluent at accomplishing certain external feats, but the accomplishment is achieved by processes that are qualitatively different, not simply quantitatively improved.

Jerome Bruner, In Search Of Mind