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Membranes are mosaics of structure and function

Membranes are mosaics of structure and function -...

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Membranes are mosaics of structure and function. A membrane is a collage of different proteins embedded in the fluid matrix of the lipid  bilayer. Proteins determine most of the membrane’s specific functions. The plasma membrane and the membranes of the various organelles each have unique  collections of proteins. There are two major populations of membrane proteins. Peripheral proteins  are not embedded in the lipid bilayer at all. Instead, they are loosely bound to the surface of the protein, often connected to integral  proteins. Integral proteins  penetrate the hydrophobic core of the lipid bilayer, often completely  spanning the membrane (as transmembrane proteins). The hydrophobic regions embedded in the membrane’s core consist of stretches of  nonpolar amino acids, often coiled into alpha helices. Where integral proteins are in contact with the aqueous environment, they have 
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Unformatted text preview: hydrophilic regions of amino acids. On the cytoplasmic side of the membrane, some membrane proteins connect to the cytoskeleton. On the exterior side of the membrane, some membrane proteins attach to the fibers of the extracellular matrix. The proteins of the plasma membrane have six major functions: Transport of specific solutes into or out of cells. Enzymatic activity, sometimes catalyzing one of a number of steps of a metabolic pathway. Signal transduction, relaying hormonal messages to the cell. Cell-cell recognition, allowing other proteins to attach two adjacent cells together. Intercellular joining of adjacent cells with gap or tight junctions. Attachment to the cytoskeleton and extracellular matrix, maintaining cell shape and stabilizing the location of certain membrane proteins....
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