Red blood cell membrane

Red blood cell membranes allow the erythrocyte to have flexibility and resiliency to undergo many passages through the spleen during its 120 day lifespan.

The ability of red blood cells to deform and return to their original biconcave disk shape is determined by the red blood cell membrane flexibility which relies on the structural and functional integrity of the membrane skeleton, and the cytoplasmic viscosity determined by the hemoglobin, and the cells surface to area volume ratio.

The red blood cell membrane is made up of alpha and beta spectrin, actin, and protein.

Red cell band 3 is the major integral membrane protein regulating exchange and facilitation of transfer of CO2 from tissues to lungs.

Ankyrin is the major connecting protein linking the membrane skeleton to the membrane bilayer.

Mutations in any of the genes that code for a major membrane proteins can alter the function and expression of such proteins, compromise the integrity of the membrane, and contribute to abnormal red blood cell morphology.

Most membrane defects or results of genetic ab2242ations of the cytoskeletal components, others represent rare disorders of cation permeability and can arise from abnormalities of the lipid bilayer or integral membrane proteins.

The red blood cell membrane consists three basic components: a lipid bilayer, transmembrane proteins and a cytoskeletal network.

The red blood cell lipid bilayer is a semipermeable, incompressible, two dimensional liquid crystal.

The red blood cell lipid bilayer is asymmetric and separates the cytoplasm from the extracellular medium.

Phosphatidylcholine (PC), sphingomyelin and the sterol cholesterol are the dominant extra leaflet components of the red blood cell lipid bilayer.

Phosphatidylserine (PS) and phosphatidylethanolamine (PE) are the dominant inner leaflet components of the red blood cell lipid bilayer.

Transmembrane proteins are solutes in a two dimensional fluid, the bilayer, and thus have varying degrees of lateral mobility in the plane of the membrane.

The major transmembrane proteins are glygoproteins, band 3 and glygophorin.

Band 3 tetramers tether the bilayer to the skeleton via an interaction between its cytoplasmic domain and ankyrin which is associated with spectrin.

The cytoskeleton is an irregular hexagonal lattice of polymeric spectrin molecules which are tied together by actin, and other proteins at junctional complexes.

The skeleton makes a two dimensional network which is very flexible and compressible.

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