The basic subunit of any living organism; the simplest unit that can exist as
an independent living system. There are many different types of cells in complex
organisms such as humans, each with specific characteristics.
Cells are surrounded by a cell membrane (and cell wall in bacteria and plants
= a membrane plus some chemically more stable structures, often mixtures of
proteins and polysaccharides) and contain all necessary elements to sustain
life; proteins, nucleic acids,
lipids, minerals, and a diverse
class of metabolites.
Cells of higher organisms (known as eukaryotes) are subdivided into
subcellular compartments called organelles such as the mitochondrion, the cell
nucleus, the endoplasmatic reticulum, the Golgi apparatus and many smaller
organelles with highly specialized functions.
While all these organelles are found in animal cells, plant cells in addition
contain a central vacuole that controls pressure to stabilize the cell and
chloroplasts, the site of photosynthesis or light dependent biosynthesis of
Source: GreenFacts, based on What is Life