Cell
The cell is the smallest unit of life capable of independently reproducing itself. It is a small, watery, compartment filled with chemical-based machinery and a complete copy of the organism's genome.
There are two main types of cells: prokaryotic[1] cells, which lack a nucleus, and eukaryotic[1] cells, with a nucleus separated from cytoplasm by a nuclear membrane.
A bacterium is a simple cell without a nucleus to protect its genetic information.
A virus requires structures in a cell's cytoplasm to assemble copies of itself.
There is no consensus on the exact number of cells in a human body, though the number ranges from 10 to 100 trillion cells.[2]
Components of a Cell
A eukaryotic cell is divided into a number of membrane bound compartments known as organelles, each with its own structure and function. In a typical cell these components are:
A prokaryotic cell lacks individual compartments.