Practice question

Self sealing of membranes is a spontaneous thermodynamic process driven by amphipathic design and the hydrophobic effect. Each phospholipid carries polar phosphate head that hydrogen bonds with water and two nonpolar tails that release ordered water clathrates when aggregated gaining entropy. Edge exposure where tails contact water creates high line tension ten to twenty piconewtons so minimizing edge length is energetically favored. Small holes close via lateral diffusion of lipids at rates near micrometer squared per second without ATP while larger wounds recruit ESCRT III CHMP4B and annexin mediated patching for excision. This principle allows artificial liposomes to form after sonication, cells to reseal after microinjection, patch clamp gigaohm seals to stabilize, and protoplasts to recover. Glycolipids protein content modulate fluidity but are not requirement for resealing. Cholesterol depletion stiffens but still reseals via phospholipids alone. Understanding hydrophobic driven self assembly clarifies why bilayers are resilient barriers and underpins technologies from liposomal vaccines mRNA delivery to membrane repair assays routinely used in cell biology laboratories worldwide.