cell

A cell is the basic unit of life in all organisms. Cells perform essential functions such as energy conversion, growth, and reproduction. The study of cells is central to biology.

Cell theory established that all organisms are composed of cells, that the cell is the basic unit of structure and function, and that new cells arise from preexisting cells. Two major cell types are recognized: prokaryotic cells, such as bacteria and archaea, which lack a membrane-bound nucleus; and eukaryotic cells, which enclose their DNA in a nucleus and contain membrane-bound organelles.

Most cells are bounded by a plasma membrane that encloses cytoplasm and cytosol. The cell interior contains organelles such as a nucleus (in eukaryotes), mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, and, in plants and algae, chloroplasts and a central vacuole. The cytoskeleton provides shape and tracks for movement. Ribosomes synthesize proteins.

Genetic material stores information as DNA, which is transcribed to RNA and translated into proteins. In prokaryotes, DNA is located in the nucleoid; in eukaryotes, in chromosomes within the nucleus. Cells metabolize nutrients, extract energy, and respond to signals through signaling pathways. Many cells also reproduce by division: mitosis in somatic cells and meiosis for gamete formation, while prokaryotes divide by binary fission.

Cells can be unicellular or multicellular. In multicellular organisms, cells differentiate into specialized types that form tissues and organs. Despite diversity, all cells share common features and arise from a common ancestry.