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".
The cell is so enormously complex that it makes a spaceship or a supercomputer look rather low-tech in comparison. --Phillip E. Johnson [1]
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.[1]
Types of cells
There are two main types of cells: prokaryotic[2] cells, which lack a nucleus, and eukaryotic[2] cells, with a nucleus separated from cytoplasm by a nuclear membrane. Each cell contains a complete copy of the organism's genome.
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.