Download Cells By the Number: Facts About the Building Blocks of Life

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Volume 9, Issue 14
Interesting
Science Facts
1.) Fleas can jump
130 times higher
than their own
height. In human
terms, this is equal
to a 6 ft person
jumping 780 ft into
the air.
Cells By the Number: Facts About the
Building Blocks of Life
By Chidinma Okparanta for the National Institutes of Health
Cells are the basic unit of life — and the focus of much
scientific study and classroom learning. Here are just a
few of their fascinating facets.
3.8 billion
That’s how many years ago scientists believe the first
known cells originated on Earth. These were prokaryotes, single-celled organisms that do not have a nucleus or other internal structures called organelles. Bacteria are prokaryotes, while human cells are eukaryotes.
2.) There are no
poisonous snakes
in Maine.
3.) The smallest
bone in the human
body is the stapes
or stirrup bone located in the middle
ear. It is approximately .11 inches
(.28cm) long.
4.) The longest
cells in the human
body are the motor
neurons. They can
be up to 4.5 ft (1.37
meters) long and
run from the lower
spinal cord to the
big toe.
5.) The human eye
blinks an average
of 4,200,000 times
a year.
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Devloping nerve cells, with the nuclei shown in yellow
Credit: Torsten Whittmann,
University of California, San Francisco
0.001 to 0.003
This is the diameter in centimeters of most animal
cells, making them invisible to the naked eye. There are
some exceptions, such as nerve cells that can stretch
from our hips to our toes, sending electrical signals
throughout the body.
1665
In that year, British scientist Robert Hooke coined the term cell to describe the porous, grid-like structure
he saw when viewing a thin slice of cork under a microscope. Today, scientists study cells using a variety of
high-tech imaging equipment as well as rainbow-colored dyes and a green fluorescent protein derived from
jellyfish.
200
That’s how many different types of cells are in the human body, including those in our skin, muscles, nerves,
intestines, blood and bones.
3 to 5
Believe it or not, that’s the approximate number of pounds of bacteria you’re carrying around, depending on
your size. Even though bacterial cells greatly outnumber ours, they’re much smaller than our cells and therefore account for less than 3 percent of our body mass. Scientists are learning more about how our body
bacteria contribute to our health.
24
This is the typical length in hours of the animal cell cycle, the time from a cell’s formation to when it splits in
two to make more cells.
120
That’s the approximate lifespan in days of a human red blood cell. Other cell types have different lifespans,
from a few weeks for some skin cells to as long as the life of the organism for healthy neurons.
50 to 70 billion
Each day, approximately this many cells die in the human body as part of a normal process that serves a
healthy and protective role. Those that die in the largest numbers are skin cells, blood cells and some cells
that line structures like organs and glands.