Normal Eukaryotic Cell

Ross Koning forwarded at message.here
Wed Oct 1 08:40:12 EST 1997


Hi David!

This is an interesting question and one could write much
about it.  When I write "typical" or typical, I hope you
will see the quotation marks I intend to use.  This is
something I say in every course about cell biology in my
plant courses.

Indeed as far as plants go, most textbooks will show some
kind of parenchyma cell as "typical." But certainly in terms
of numbers of plant cells on earth, I'd bet that most of them
are dead with no cytoplasm and only walls left (ie secondary
xylem in trees!).  The "typical" plant cell will usually show
chloroplasts.  While certain plant cells have chloroplasts,
the rest have other types of plastids instead.  Root and stem
parenchyma, collenchyma, immature vascular cells, mature phloem
cells, most dermal cells, all meristematic cells...these all
lack chloroplasts!

So you have an interesting question...but if we limit the
discussion to LIVING cells (NOT Xylem Elements, Cork Cells, etc.)
and include all eukaryotic organisms, then we would have the
cell membrane and nucleus (except during mitosis in many organisms),
some kind of ribosomes in a cytosol...but going any further might
leave some organisms/cells out.  MOST will have mitochondria of
one form or another...but there could be organisms functioning
in some obligate fermentation mode that have no mitochondria.
Cytoskeletal elements might be common to many, maybe even to all
in at least some form or some phase of development.

There will be exceptions to all rules, though.   A good example is
the human red blood cell (lacking nucleus) and phloem sieve tube
element (lacking most organelles). So you have to be sure to
distinguish "typical" from "least common denominator".  Anyway it
makes for a fun discussion with students!

ross


_______________________________________________________________
Ross Koning                 | koning at ecsu.ctstateu.edu
Biology Department          | http://koning.ecsu.ctstateu.edu/
Eastern CT State University | phone: 860-465-5327
Willimantic, CT 06226 USA   | fax: 860-465-4479
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