BIO152H5 Chapter Notes - Chapter 6: Lipid Bilayer, Membrane Fluidity, Facilitated Diffusion
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. Lipids are carbon-containing compounds that are found in organisms and that are largely nonpolar and hydrophobic. Hydrocarbons are molecules that contain only carbon and hydrogen. Lipids have a major hydrocarbon component called a fatty acid. 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. Lipids are defined by solubility rather than by chemical structure, so their structures vary widely.
