Practice question

Quantitative lipidomics mammalian plasma membrane places phospholipids dominant class representing fifty to sixty mole percent total lipid exceeding sterols thirty to forty sphingolipids fifteen to twenty glycolipids two to five minor outer leaflet exclusively. Within phospholipids phosphatidylcholine thirty to forty percent phosphatidylethanolamine fifteen to twenty five phosphatidylserine ten fifteen phosphatidylinositol five phosphatidic acid lysophospholipids minor species synthesized Kennedy CDP choline ethanolamine pathways PS synthase base exchange PSS1 PSS2 in ER mitochondria associated membranes MAM regulated by substrate availability. Abundance reflects role bilayer matrix providing lateral solvent integral proteins barrier function permeability regulation and signaling platform via PIP2. Sphingolipids crucial rafts less abundant overall but functional regulatory rafts signaling, cholesterol abundant single species class distinct sterol not phospholipid class. Hence when question asks most abundant class answer phospholipids aggregate consistent extraction Folch method yields phospholipid fraction largest. Understanding hierarchy informs reconstitution experiments PC PE mixture mimics physiological fluidity permeability and explains phospholipid biosynthesis defects severe growth phenotypes yeast cho mutants hampering proliferation membrane expansion during cell cycle progression for exams and synthetic biology liposome engineering.