The inner leaflet monolayer of the human erythrocyte

Last updated: 4/29/2023

The inner leaflet monolayer of the human erythrocyte membrane consists predominantly of phosphatidylethanolamine and phosphatidylserine The outer leaflet consists predominantly of phosphatidylcholine and sphingomyelin Although the phospholipid components of the membrane can diffuse in the fluid bilayer this sidedness is preserved at all times How is this sidedness preserved An increase in cytosolic calcium concentration prevents membrane phospholipids from crossing the bilayer O Scramblases move phosphatidylcholine and sphingomyelin to the outer membrane The energetic cost of moving the highly polar sometimes charged head group through the hydrophobic interior of the bilayer is prohibitive Floppases move phosphatidylethanolamine and phosphatidylserine to the inner leaflet so that phosphatidylserine does not trigger apoptosis