BIO152H5 Study Guide - Lipid Bilayer, Membrane Fluidity, Cell Membrane
Document Summary
Phospholipids are amphipathic lipid molecules they are part hydrophobic and part hydrophilic. Plasma membranes are made up of bilayers of phospholipids. Ions and molecules diffuse spontaneously from regions of higher concentration to regions of lower concentration a process called diffusion. Movement of water across a plasma membrane is a special case of diffusion called osmosis. In cells, membrane proteins are responsible for the passage across membranes of ions and large and/or polar molecules in the processes of facilitated diffusion and active transport. A fatty acid is a hydrocarbon chain bonded to a carboxyl (cooh) functional group. Hydrocarbons are the reason that lipids do not dissolve in water. One important steroid in mammals is cholesterol: phospholipids consist of a glycerol that is linked to a phosphate group (po42-) and to either two chains of isoprene or two fatty acids. The structure of membrane lipids: membrane-forming lipids are amphipathic, containing both hydrophobic and hydrophilic regions.
