A
small, usually microscopic, membrane-bound
structure that is the fundamental unit of all living things. Organisms can be
made up of one cell (unicellular; bacteria,
for example) or many cells (multicellular; human beings, for example, which
are made up of an estimated 100,000 billion cells.)
A
membrane-bound
unit, typically microns
in diameter. All plants and animals are made up of one or more cells
(trillions, in the case of human beings). In general, each cell of a
multicellular organism contains a nucleus
holding all of the genetic information of the organism.
