BIOSC 0150 Lecture Notes - Lecture 7: Lipid Bilayer, Osmosis, Glycerol

• School: Pitt
• Department: Biological Sciences
• Course: BIOSC 0150
• Professor: Mc Greevy Erica

Document Summary

Membranes are also permeable to h2o and small, uncharged polar molecules like glycerol: osmosis: the diffusion of water when solutes cannot cross the membrane. Osmosis works to even the concentration by moving to the region with more solute. These terms are relative and usually established in terms of inside solution vs outside solution. Osmosis can cause vesicles to shrink if the water moves out of the cell or burst if water moves into the cell. Membranes are not very permeable to large, uncharged polar molecules (ex: sugars) or ions. Proteins are required to move these molecules: transmembrane proteins are recognizable by large sequences of nonpolar r groups (~20 residues). These hydrophobic regions allow the protein to integrate itself into the lipid bilayer. Transport falls into three categories: diffusion, facilitated diffusion, and active transport. Facilitated diffusion: movement down a gradient through a channel or carrier protein. The gradient can be concentration or electrochemical (related to concentration and charge of ions).