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ashone24 (Chapter 24 ** )

Chapter Twenty-four — Cells

A Short History of Nearly Everything – by Bill Bryson

Chapter 24 — Cells

  • Life starts with a single cell.  The first cell splits to become two and the two become four and so on.  After just 47 doublings, you have 10 thousand trillion (10,000,000,000,000,000) cells in your body and you are ready to spring forth as a human being.
  • If the DNA contained in just one cell was uncurled and laid out to its full length, it would measure 6 feet in length.  Thus, the DNA in one human adult, stretched straight, would reach to the Moon 6,000 times!
  • To build the most basic cell (for example, a yeast cell), you would have to miniaturize about the same number of components as are found in a Boeing 777 jetliner and fit them into a sphere just 5 microns across.
  •  Each human being is a country of 10 thousand trillion cells, each devoted in some intensively specific way to your overall well-being.  There is not one thing that you cells don’t do for you.
  • Each of us has at least 200,000 different types of protein laboring away inside us, and so far we understand what no more than about 2% of them do.
  • The size of cells varies greatly.  When a single sperm cell confronts an egg cell, the egg cell is 85,000 times bigger than the sperm.
  • On the average, a human cell is about 20 microns wide, which is too small to be seen but roomy enough to hold 1000’s of complicated structures like mitochondria, and millions upon millions of molecules.
  • All of your superficial skin cells are dead.  Every inch of our skin surface is deceased.  The average human adult is carrying around about 5 pounds of dead skin, of which several billion tiny fragments are sloughed off each day.  The dust that accumulates on the mantle in our homes is largely composed of dead skin cells.
  • Most living cells live more than a month, but there are some exceptions.  Liver cells can survive for years.  Brain cells last as long as you do.  You are issued 100 billion of them at birth, and that is all we ever have.  We lose about 500 brain cells an hour during our lives.
  • There isn’t a single bit of any of us (not even a stray molecule) that was part of us nine years ago.  On a cellular level, all of us are youngsters.
  • Leeuwenhoek, one of the early discoverers of microscopes, calculated that there were 8,280,000 protozoa in a single drop of water.  That is more than all the people in the country of Holland.
  • The cell has been compared to a “complex chemical refinery” and to a “vast, teeming metropolis”.
  • If you could visit the inside of a cell, you would not like it.  Blown up to a scale where molecules were the size of peas, the cell itself would be a sphere about half a mile across.  Within it, millions upon millions of objects (some the size of basketballs and others the size of cars) would whiz about like bullets.  There wouldn’t be a single place you could stand without being pummeled and ripped 1000’s of times each second, from every direction.
  • Proteins are especially lively.  They spin and pulsate and fly into each other up to a billion times a second.  Enzymes, themselves a type of protein, dash everywhere, performing 1000’s of tasks a second.
  • Cells are composed of millions of objects (lysosomes, ribosomes, endosomes, ligands, peroxisomes, proteins, etc.) bumping into millions of other objects and performing mundane tasks.
  • Your heart needs to pump 75 gallons of blood an hour, 1,800 gallons every day, 657,000 gallons in a year, to keep all your cells supplied with oxygen.
  • ATP (adenosine triphosphate) can be compared to little battery packs that move through the cells, providing energy for all the cellular processes.  A typical cell will have about one billion ATP molecules in it, and in two minutes every one of them will have been drained dry and another billion will have taken their place.  Every day you produce and use up a volume of ATP equivalent to about half your body weight.
  • In ways that we have barely begun to understand, trillions upon trillions of reflexive chemical reactions add up to a mobile, thinking, decision-making YOU.  For that matter, the same can be said of an incredibly organized dung beetle.  Every living thing is a wonder of atomic engineering.

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