The basic unit of life, capable of growing and multiplying.
All living things are either single, independent cells or aggregates
of cells. A cell is composed of cytoplasm and a nucleus, and is
surrounded by a membrane or wall. Cells can be categorized by the
presence of specific cell surface markers called .
Cell Membrane . A two-layered structure,
composed of fatty material, that occurs within and surrounds all
cells. Most natural membranes have various proteins, such as receptors
and enzymes, embedded in them.
Examples of cells include :