Practice question

Efficient movement lipids between organelles employs both vesicular carriers clathrin COPII COPI and non vesicular lipid transfer membrane contact sites where domain organization guides sorting specificity and lipid gradients. Vesicular pathway buds donor via coat proteins packaging lipids proteins, while lipid driven sorting trans Golgi network concentrates sphingolipids cholesterol GPI anchored proteins into rafts destined apical plasma membrane demonstrated sorting influenza hemagglutinin placental alkaline phosphatase independent cytosolic sorting signals tyrosine dileucine. Flotillin caveolin oligomers stabilize such domains recruiting cargo clustering via oligomerization forming carriers. Non vesicular transfer uses lipid transfer proteins CERT ceramide FAPP2 glucosylceramide OSBP ORP family sterol PI4P exchange at ER Golgi MCS tethering VAPA VAPB. Cytoskeleton provides tracks vesicle motors kinesin dynein, ribosomes synthesize proteins not traffic lipids. Thus lipid rafts function sorting platforms influencing lipid flow directionality polarity signaling, linking membrane biophysics secretory pathway organization relevant congenital disorders glycosylation lipid storage diseases affecting trafficking polarity maintenance cell migration immune synapse formation concepts examined cell biology biochemistry trafficking questions thoroughly for organelle communication mechanisms.