BIOL 203 Lecture Notes - Lecture 6: Lipid Bilayer, Tight Junction, Amphiphile
Document Summary
Plasma membrane: separates living cell from surrounding, selective permeability. Allows some substances to cross more easily than others: made up of a mosaic phospholipid bilayer and proteins. Phospholipids are amphipathic: hydrophobic and hydrophilic regions. Proteins also are amphipathic: hydrophobic amino acids on inside protected by hydrophilic on outside. Originally thought to be a sandwich model, proteins inside of bilayer. Figured out it was uid mosaic: freeze-fracture. Phospholipids can move laterally within membrane: rapid: 10^7 times per second, some proteins as well. Some are highly directed from being connected to cytoskeletal bers. Experiment: label plasma membranes with two different markers, combine two cells, proteins wind up mixed on nal product showing uidity. Temperatures: cool temperatures: membranes switch from uid to solid state. Needs to be uid in order to function. Tuesday, september 29, 2015: affects permeability & protein function. Temperature at which membrane will solidify depends on types of lipids: unsaturated fatty acids will stay more uid than saturated fatty acids.
