From Madigan MT, Bender KS, Buckley DH, Sattley WM, Stahl DA. Chapter 2: Microbial Cell Structure and Function. In: Brock Biology of Microorganisms. 15th ed. Global ed. Pearson; 2018.
“The cytoplasmic membrane surrounds the cytoplasm—the
mixture of macromolecules and small molecules inside the cell—
and separates it from the environment. The cytoplasmic mem-
brane is physically rather weak but it is an ideal structure for its
major cellular function: selective permeability. In order for a cell
to grow, nutrients must be transported inwards and waste products
outwards. Both of these events occur across the cytoplasmic mem-
brane. A variety of proteins located in the cytoplasmic membrane
facilitate these reactions, and many other membrane proteins
play important roles in energy metabolism.”
"The cytoplasm of prokaryotic cells maintains a high concentra-
tion of dissolved solutes that creates significant osmotic pressure—
about 2 atm (203 kPa); this is about the same as the pressure in an
automobile tire. To withstand these pressures and prevent burst-
ing—a process called cell lysis—most cells of Bacteria and Archaea
have a layer outside the cytoplasmic membrane called the cell wall.
Besides protecting against osmotic lysis, cell walls also confer
shape and rigidity on the cell. "
“ “The cell wall and cell membrane of bacteria form the envelope. Together, they control the movement of solutes into and out of the cell.”
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