Practice question

Early membrane theories debated whether lipid or protein formed continuous barrier. Charles Overton's permeability studies correlated anesthetic potency with oil solubility hinting at lipid membrane, but direct bilayer demonstration came from Evert Gorter and François Grendel at Leiden in 1925. They extracted erythrocyte lipids with acetone, spread them as monolayer at Langmuir trough air-water interface, and measured area at collapse pressure. Total lipid area approximated double surface area of red cells used, leading to inference that membrane consists of two opposed lipid layers with non-polar tails inward, polar heads outward. Despite experimental limitations underestimating lipid amount and ignoring protein contribution, conceptual breakthrough established lipid bilayer as core structure. Subsequent refinements included Davson-Danielli sandwich model proposing protein layers coating bilayer based on surface tension, Robertson's unit membrane EM trilaminar interpretation, and finally Singer-Nicolson fluid mosaic incorporating proteins within fluid lipid sea. Thus Gorter-Grendel experiment stands as first bilayer proposal foundational for modern membrane biology.