A Short History of Nearly Everything [PDF]

Summary
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A Short History of Nearly Everything – Book

You possess “some few hundred” different types of cell, according to the Belgian biochemist Christian de Duve, and they vary enormously in size and shape, from nerve cells whose filaments can stretch to several feet to tiny, disc-shaped red blood cells to the rodshaped photocells that help to give us vision.

They also come in a sumptuously wide range of sizes—nowhere more strikingly than at the moment of conception, when a single beating sperm confronts an egg eighty-five thousand times bigger than it (which rather puts the notion of male conquest into perspective). On average, however, a human cell is about twenty microns wide—that is about two-hundredths of a millimeter—which is too small to be seen but roomy enough to hold thousands of complicated structures like mitochondria, and millions upon millions of molecules.

In the most literal way, cells also vary in liveliness. Your skin cells are all dead. It’s a somewhat galling notion to reflect that every inch of your surface is deceased. If you are an average-sized adult you are lugging around about five pounds of dead skin, of which several billion tiny fragments are sloughed off each day. Run a finger along a dusty shelf and you are drawing a pattern very largely in old skin.