Membrane Structure and Function: Key Concepts for the Final Exam

The hydrophobic effect = the membrane organizing factor The hydrophobic effect is a unique organizing force, based on repulsion by the solvent instead of attractive forces at the site of organization. It is responsible for assembly of membranes of cells and intracellular compartment s, and the absence of strong attractive forces makes the membranes fluid and deformable. What is the critical concentration of micelle formation (CMC) for a detergent? Critical micelle concentration is minimum concentration at which the emulsifiers in a detergent will coalesce i n to membrane structu res of globes, rod or sheets with their hydrophobic ends on the inside of the membrane and their hydrophilic ends on the outside. Detergents, surfactants, and their behavior at the air -water interface. How do they decrease tension? Surfactants first gather on the surface of the water to form a layer at the water -air interface, with the hydrophilic heads towards the water, and the hydrophobic ta ils in the air. This results in a decrease in water surface tension, a key property of surfactants . Why do lipids have two aliphatic chains? It enhances their ability to form stable structures like lipid bilayers, crucial for the integrity and function of cellular membranes. Allows lipids to effectively interact with other lipid molecules and create stable lipid bilayers. In a bilayer, lipid molecules align with their hydrophobic tails facing inward forming a nonpolar region that excludes water and the heads face outward. Serves as abarrier that regulates the passage of molecules into and out of cells. How is it related to solubility? Recognize the main glycerophospholipid species: PC, PE, PS, PI, and cardiolipin. Name a phospholipid that has more than two aliphatic chains. Recognize sterols. Presence of two aliphatic chains in lipids is related to their solubility properties. Lipids with two hydrophobic chains are generally less soluble in water due to their nonpolar nature. Allows them to aggregate together in aqueous environments, forming structures like lipid bilayers, which effectively separate hydrophobic regions from water. The main glycerophospholipid species: - PC: Phosphatidylcholine - PE: Phosphatidylethanolamine - PS: Phosphatidylserine - PI: Phosphatidylinositol - Cardiolipin: diphosphatidylglycerol A phospholipid that has more than two aliphatic chains is a triglyceride (glycerol molecule bonded to three fatty acid chains) Sterols are a type of lipid characterized by a four-ring structure; the most well-known sterol is cholesterol. Sterols play vitals roles in maintaining membrane fluidity and are precursors to steroid hormones and bile acids. What makes us think of the lipid bilayer as a two -dimensional liquid?