The cell
A cell is the smallest unit that counts as alive: a volume of chemistry enclosed by a membrane that keeps its inside different from its outside. Cell theory, stated in the late 1830s, holds that every organism is made of one or more cells and that every cell comes from a pre-existing cell. Bacteria and archaea are single cells without a nucleus; plants, animals, and fungi are built from cells that keep their DNA in a nucleus.
Why it matters
It sets the boundary that the rest of biology works across: everything from metabolism to heredity happens inside cells or between them.
Also written: cells, cell theory
Where it comes up
Read about The cell on Wikipedia
Sources
- Cell (biology) Wikipedia
- The Cell: A Molecular Approach NCBI BookshelfA full university textbook, free to read; the opening chapters cover cell structure without assuming chemistry.
- Cell Theory WikipediaThe history of how the claim was assembled from microscope work.
