Most unicellular organisms are classed as microorganisms. Organisms can be classified as unicellular (consisting of a single cell such as bacteria) or multicellular (including plants and animals). Electron microscopy gives a much higher resolution showing greatly detailed cell structure.

Most plant and animal cells are only visible under a light microscope, with dimensions between 1 and 100 micrometres.

Most cells are measured in micrometers due to their small size. Cells are capable of specialization and mobility within the cell. Ĭells can acquire specified function and carry out various tasks within the cell such as replication, DNA repair, protein synthesis, and motility. The term comes from the Latin word cellula meaning 'small room'.

Every cell consists of a cytoplasm enclosed within a membrane, and contains many biomolecules such as proteins, DNA and RNA, as well as many small molecules of nutrients and metabolites. The cell is the basic structural and functional unit of life forms.

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