Structures internal to the cell wal2

Structures internal to the cell wal2 - The most important...

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Structures internal to the cell wall, comparison with eucaryotes The plasma (cytoplasmic) membrane or prokaryotic cells is composed primarily of phospholipids and proteins (Tortora et al. Fig 4.13) - 50% or more of the mass of the bacterial plasma membrane may be protein = This is greater than the amount of protein in eucaryotic plasma membranes, perhaps because many of the functions of organelles in eucaryotes are assumed by the plasma membrane of prokaryotes = Also in contrast to eucaryotic plasma membranes, prokaryotic plasma membranes usually lack sterols - The plasma membrane is a fluid mosaic structure, in which phospholipids and proteins are able to move freely in two dimensions - The proteins in the membrane can be arranged in a variety of ways, depending on their functions (Tortora et al., Figure 4.13b) = peripheral proteins are loosely held on the inner surface of the membrane = integral proteins are embedded in the phospholipid bilayer, and may penetrate it completely
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Unformatted text preview: The most important function of the plasma membrane is to serve as a selectively permeable (semipermeable) barrier through which materials enter and exit the cell- The permeability of the membrane depends on several factors = Not surprisingly, small molecules pass through the membrane more easily than larger molecules = In general, the membrane is more permeable to hydrophobic molecules than to hydrophilic molecules = Some of the integral proteins are carriers that selectively promote passage of certain molecules- Prokaryotic plasma membranes are also important sites for energy metabolism = These functions are carried out by integral and peripheral membrane proteins = Respiration and photosynthesis, compartmentalized in organelles of eucaryotic cells, are carried out in plasma membranes of prokaryotes- Antimicrobial agents, including disinfectants and some antibiotics, may exert their effects through disruption of the plasma membrane...
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