ARCHAEAL CELL MEMBRANE

 ARCHAEAL CELL MEMBRANE

·       The Cytoplasmic membrane of Archaea is formed from either Glycerol diethers, which have 20 carbon side chains, or diglycerol tetraethers, which have 40 carbon side chains.

·    In the Tetraether lipid, the ends of the phytanyl side chains that point inward from each glycerol molecule are covalently linked. This forms a Lipid monolayer instead of a Lipid bilayer membrane.

·   In contrast to Lipid bilayers, Lipid monolayer membranes are extremely resistant to heat and are therefore widely distributed among Hyperthermophilic Archaea (organisms that grow best at temperatures above 80 °C).

·   Membranes with a mixture of bilayer and monolayer character are also possible, with some of the opposing hydrophobic groups covalently bonded and others not.

Difference between Bacterial and Archaeal Cell membrane

·      There are several characteristics of the Plasma membrane that are unique to Archaea, setting them apart from other domains.

·    One such characteristic is chirality of the glycerol linkage between the phopholipid head and the side chain. In archaea it is in the L-isomeric form, while bacteria and eukaryotes have the D-isomeric form.

·    A second difference is the presence of an ether-linkage between the Glycerol and the side chain in Archaea, as opposed to the ester-linked lipids found in bacteria and eukaryotes. The ether-linkage provides more chemical stability to the membrane.

·       A third difference is associated with the side chains. Unbranched fatty acids in Bacteria and Eukaryotes, while isoprenoid chains are found in Archaea. These isoprenoid chains can have branching side chains.

Finally, the Plasma membrane of Archaea can be found as Monolayers, where the Isoprene chains of one Phospholipid connect with the Isoprene chains of a Phospholipid on the opposite side of the membrane. Bacteria and Eukaryotes only have lipid bilayers, where the two sides of the membrane remain separated.