Hypothesis: The presence of membrane-bound organelles and nucleus has allowed eukaryotes to become multicellular.

Hypothesis: The presence of membrane-bound organelles and nucleus has allowed eukaryotes to become multicellular.

 

            A eukaryote is any life-form consisting of one or more cells that contain a membrane-bound nucleus and organelles separate from the plasma membrane enveloping the cell. Prokaryotes on the other hand do not have membrane-bound organelles and nucleus. Prokaryotes typically do not have membrane-bound organelles but the cell membrane may, as in photosynthetic bacteria, have intricate infoldings to increase surface area for various chemical processes. Well organized and delimited nuclei are lacking in certain simple organisms but distinct genetic material is distributed through the cytoplasm although it is not limited by a membrane.

The partitioning of the cytoplasm achieved by membrane-bounded organelles and nucleus in eukaryotes enhances the efficiency of countless chemical reactions by amplifying the area of physiologically active interfaces within the cell. This facilitates control of cell metabolism by enabling the cell to maintain a separation of enzymes and their substances at some times, and at other times, permitting their controlled interaction by varying the permeability of a particular membrane or the rate of active transport across it. Most of the physiologically important processes take place at surfaces and interfaces, and the demonstration of extensive compartmentalization of the cytoplasm by membranes in eukaryotic cells has been an important contribution for eukaryotes becoming multicellular.

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