Membrane

Membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Biological membranes include cell membranes (outer coverings of cells or organelles that allow passage of certain constituents); nuclear membranes, which cover a cell nucleus; and tissue membranes, such as mucosae and serosae. Synthetic membranes are made by humans for use in laboratories and industry (such as chemical plants).

Biological membranes

Biological membranes are an enclosing or separating membrane that acts as a selectively permeable barrier within living things. Biological membranes, in the form of eukaryotic cell membranes, consist of a phospholipid bilayer with embedded, integral and peripheral proteins used in communication and transportation of chemicals and ions. The bulk of lipid in a cell membrane provides a fluid matrix for proteins to rotate and laterally diffuse for physiological functioning. Proteins are adapted to high membrane fluidity environment of lipid bilayer with the presence of an annular lipid shell, consisting of lipid molecules bound tightly to surface of integral membrane proteins. The cellular membranes should not be confused with isolating tissues formed by layers of cells, such as mucous membranes and basement membranes.

Synthetic membranes

Synthetic membranes are engineered structures with pores or spaces for separation or reaction purposes. They can be created from organic or inorganic materials including solids such as metal or ceramic, homogeneous films such as polymers, or asymmetric structures such as coated glass. The voids in membranes used for separation processes can be as small as a fraction of a nanometer to larger than a micron and can be of different shapes such as cylindrical or irregular depending on the processing method used for their formation.

See also

• Cell membrane
• Nuclear membrane
• Mucous membrane
• Basement membrane
• Phospholipid bilayer
• Integral membrane protein
• Peripheral membrane protein

References

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Membrane

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  Schematic of size-based membrane
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  Hollow fiber membrane wall
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  Constant TMP and constant Flux
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  Cross-flow dead-end
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  Waste Hierarchy