The correct answer is 0.1 - 5.0 ?m in diameter.Organisms that lack a membrane-bound nucleus are called prokaryotes.A prokaryotic cell does not contain a well-defined nucleus.All prokaryotes have a cell wall surrounding the cell membrane except in mycoplasma.The nucleolus is absent in prokaryotic cells.The fluid matrix filling the prokaryotic cell is the cytoplasm.Prokaryotic cells are significantly smaller than eukaryotic cells with 0.1 - 5.0 ?m in diameter.Membrane-bound cell organelles are absent in prokaryotes.In prokaryotes, cell division takes place by fission or budding.Blue-green algae, bacteria, and mycoplasma are examples of prokaryotes.Additional Information Organisms that have membrane-bound nuclei are called eukaryotes.In eukaryotes, cell division takes place by mitosis or meiosis.All living organisms are made up of cells.?Cell is the basic structure and functional unit of life.The study of cells is called cytology.The word 'cell' was first coined by Robert Hook in 1665.