What is a cell?
Cell is the basic structural and functional unit of living organisms. It is the building block of life. Some organisms are unicellular (single celled) like bacteria while others are multi-cellular like humans. Human beings have an estimated 100 trillion cells and the typical cell size is 10 micro-meters with cell mass of 1 nanogram. The largest known cell is the unfertilized Ostrich egg cell.
The word ‘cell’ comes from the Latin cellula, meaning ‘a small room’. The cell theory developed by Matthias Jakob Schleiden and Theodor Schwann states that all organisms are composed of one or more cells and all cells arise from preexisting cells. Vital functions of an organism occur within cells, and all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.
A group of cells having similar function constitute to form a tissue. Various tissues having coordinated function form organs which inturn constitute the body system.
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