2) Assignment of membrane lipids As PL synthesis takes play in the cytosolic leaflet of the ER bilayer, therefore there are several mechanisms to transfer some of the newly formed PL molecules to the lumenal half of bilayer. The active proteins, PL-translocators across the bilayer (flippases) catalyze the rapid translocations( 100,000 times within mininues)of some of these lipid molecules, particularly PC, menbrane PL the latter move into the opposite leaflet resulting in even growth of both halves of the bilayer The menbrane PL asymmetry are also maintained by the proteins(translocase, floppase, scramblase etc. ) and the lateral movement of menbrane Pl as well The changes of lipid composition of membrane take place as membrane flows through the cell between different organelles and as the modify lipids already present within a membrane, converting one type of PL to another by the organelles themselves
2) Assignment of membrane lipids As PL synthesis takes play in the cytosolic leaflet of the ER bilayer, therefore there are several mechanisms to transfer some of the newly formed PL molecules to the lumenal half of bilayer. The active proteins, PL-translocators across the bilayer (flippases) catalyze the rapid translocations (~ 100,000 times within mininues) of some of these lipid molecules, particularly PC, menbrane PL. the latter move into the opposite leaflet, resulting in even growth of both halves of the bilayer. The menbrane PL asymmetry are also maintained by the proteins (translocase, floppase, scramblase etc.) and the lateral movement of menbrane PL as well. The changes of lipid composition of membrane take place as membrane flows through the cell between different organelles and as the modify lipids already present within a membrane, converting one type of PL to another by the organelles themselves
Phospholipid synthe Newly synthesized lipids added only to cytosolic half of bilayer Growth of both halves of phospholipid bilayer
1122 ZWAAL AND SCHROTT prothrombin MACROPHAGE budding thrombin vesicle Fc G 222 nx/ e scramblase translocase floppase cytoskeleton 2+ Ca alain ATP ADP
Cells contain phospholipid exchange proteins whose function is to transport specific Pl through the aqueous cytosol from one type of membrane compartment to another, particularly, from er to mitochondria and chloroplasts
Cells contain phospholipid exchange proteins whose function is to transport specific PL through the aqueous cytosol from one type of membrane compartment to another, particularly, from ER to mitochondria and chloroplasts
PS M 8左西节 Ic retculum s