🚀 go-pugleaf

In article <C01ws8.CIu@iat.holonet.net> ken@iat.holonet.net 
    (Ken Easlon) writes:

>The next question (which should have an answer in host of textbooks, but
>unfortunately none which I've been able to lay my hands on): What is the
>weight of a typical eukaryotic cell, or alternately, what is the total
>number of cells in the human body?

It might help to know what exactly you want from the information.  A
back of the envelope calculation for the weight of a cell is pretty
simple, but the variance in cell weights even in a single animal can
be quite considerable.  For a ball park number, you can approximate a
cell as a sphere with a diameter of around 30 micrometers, and a
density somewhat higher than that of water.  The mass of this model
cell would be roughly:

4/3 Pi (30E-6)^3 (1.5 g/cc) ~ 200 picograms (assuming I haven't made
                                             any gross mistakes :-)

I suspect that that value could be off by a factor of a thousand or
more (too high or too low) for any given cell, however.

As for your auxiliary question, I hope that you weren't planning on
taking the number of cells and dividing the average person's weight by
that number.  Much of your body is acellular.  For example, (and this
is just *one* example) your blood is only about 40-45% cells by volume
(the other 55-60% is plasma, which is mostly water with various salts
and proteins floating around in it).  And furthermore, of the 40% of
your blood that is cellular, nearly all of that is non-nucleated
erythrocytes (red blood cells).  Given your other questions, I suspect
that's something that you might want to know.  

So where are you headed with this?

>Ken Easlon
>ken@holonet.net

Mickey Rowe     (rowe@pender.ee.upenn.edu)