Preface to GI#4: The Scales of a Human Cell – A Prelude to Great Idea #4, Life as Chemistry: Order from Chaos

Paul Nurse’s Great Idea #4, Life as Chemistry, is probably challenging for many—if not most—readers.  One possible reason is that the author describes the possible “maelstrom” of activity that continually takes place continuously in a nucleated cell.  He then describes the multiple organelles and other structures within the cell that contain that maelstrom and thus ensure that the cell—whether from the heart, the brain or the skin—ceaselessly and accurately performs the activities that ensure its organism’s life.  How can all of this be contained in such a tiny cell. 

Although incredibly small when compared to a human body, the average human has a diameter of about 20 micrometers. But how do we visualize something that is 20 micrometers in diameter? Understanding the scales of life leads to the conclusion that the cell is quite large.  But what is the scale of life?  Perhaps the following table should help. 

What are the Scales of the Human Body?  

·    Our tissues and organs—the largest components of our bodies—are within the meter scale. 

·   Our eyes, however, are about 24 millimeters—a little less than 1 inch—in diameter, putting them in the millimeter scale. 

·   The nucleated cells in our body are within the micrometer scale (there are 1 million micrometers in a meter).

·   The molecules in our cells are within the nanometer scale (there are 1 billion nanometers in a meter)  

Imagining one thousandth of a meter may be difficult, but we can actually see the relative size of a millimeter on a metric yardstick.  But how do we visualize 1 millionth of a meter?  The chart below—the center of which is 1 meter—may help. 

UP↑

Each step upward entails multiplying the base value—where you start--by 1000.  One step up from 1 meter multiplies 1 meter by 1000 and results in 1000 meters, a kilometer. Taking two steps up results in 1 million meters, 1000 kilometers or about 621.4 miles.  The fourth step up would result in 1 trillion meters or 621.4 million miles!  

DOWN↓

Each step downward divides the base value by 1000. If starting with a base value of 1 meter, the first step down, 1 thousandth of a meter, results in 1 millimeter which we can observe on a metric yardstick. The next step down, to 1 millionth of a meter, results in 1 micrometer.  The third step down, 1 trillionth of a meter, results in in one nanometer.  

Going down 2 steps from a base value creates the same proportional relationship as going up 2 steps.  Starting at 1 meter and going up two steps would take you to 1 million meters, about 621.4 miles.  Imagine trying to find a 1-meter object somewhere along that stretch of highway.  the same sense of vastness applies when going down 2 steps: from 1 meter to 1 micrometer. A micrometer is as incredibly small, compared to a meter, as 621.4 miles is unbelievably large compared to 1 meter.  

Comparative Scales: From 1 Picometer to 1 Billion Kilometers  

(1/1,000th Smaller for Each Step Down) ↓ 

1 billion kilometers = 1 trillion meters (621.4 million miles)

1 million kilometers = 1 billion meters (621,400 miles)

1,000 kilometers = 1 million meters (621.4 miles)

1 kilometer = 1,000 meters (.621 mile)

1 meter = 1,000 millimeters

1 millimeter = 1,000 micrometers

1 micrometer = 1,000 nanometers

1 nanometer = 1,000 picometers

1 picometer = 1,000 femtometers                  

↑ (1,000 Times Bigger for Each Step Up)