Sunday, December 11, 2016

Cytoplasmic Membrane

The plasma membrane or bacterial cytoplasmic membrane is composed of a phospholipid bilayer and thus has all of the general functions of a cell membrane such as acting as a permeability barrier for most molecules and serving as the location for the transport of molecules into the cell. In addition to these functions, prokaryotic membranes also function in energy conservation as the location about which a proton motive force is generated. Unlike eukaryotes, bacterial membranes (with some exceptions e.g. Mycoplasma and methanotrophs) generally do not contain sterols. However, many microbes do contain structurally related compounds called hopanoids which likely fulfill the same function. Unlike eukaryotes, bacteria can have a wide variety of fatty acids within their membranes. Along with typical saturated and unsaturated fatty acids, bacteria can contain fatty acids with additional methyl, hydroxy or even cyclic groups. The relative proportions of these fatty acids can be modulated by the bacterium to maintain the optimum fluidity of the membrane (e.g. following temperature change).


As a phospholipid bilayer, the lipid portion of the outer membrane is impermeable to charged molecules. However, channels called porins are present in the outer membrane that allow for passive transport of many ions, sugars and amino acids across the outer membrane. These molecules are therefore present in the periplasm, the region between the cytoplasmic and outer membranes. The periplasm contains the peptidoglycan layer and many proteins responsible for substrate binding or hydrolysis and reception of extracellular signals. The periplasm is thought to exist in a gel-like state rather than a liquid due to the high concentration of proteins and peptidoglycan found within it. Because of its location between the cytoplasmic and outer membranes, signals received and substrates bound are available to be transported across the cytoplasmic membrane using transport and signalling proteins imbedded there.

Related Posts:

  • Cytoplasm Cytosol is the water-like fluid found in bacterial cells. The cytosol contains all the other internal compounds and components the bacteria needs for survival. The fluid and all its dissolved or suspended particles is called… Read More
  • Bergey’s Classification of Bacteria According to Bergey’s manual  bacteria are classified by cellular wall characteristics and are separated in 4 large groups: Gram negative Eubacteria which has cellular wall Gram positive Eubacteria which has cellular wa… Read More
  • Eubacteria and Archaebacteria Archaebacteria are the oldest living organisms on earth. They are prokaryotes and unicellular. Archaebacteria are found in very harsh conditions (such as at the bottom of the sea or in volcanic vents). This is thought to be … Read More
  • Nucleus The nucleoid (meaning nucleus-like) is an irregularly-shaped region within the cell of a prokaryote that contains all or most of the genetic material, called genophore. In contrast to the nucleus of a eukaryotic cell, it is … Read More
  • Learning Outcome Bacterial cell as prokaryote cell in all the ways is simple then eukaryote cell, with a exclusion: prokaryote cell has his membrane is more complicated.  After completing this module student will be able to: Know the… Read More

0 comments:

Post a Comment