BI110 Lecture Notes - Lecture 14: Unsaturated Hydrocarbon, Lipid Bilayer, Alkane
Document Summary
Degree of unsaturation affects fluidity: viscous, saturated hydrocarbon tails, not fluid, fluid, unsaturated hydrocarbon tails with kinks. Minimizes motion of fatty acids that leads to leakage. At cold temperatures, it keeps the phospholipids from packing together too tightly. Can be driven by diffusion: diffusion: net movement of a substance from a region of higher to lower concentration. Primary mechanism of solute movement within a cell and between cellular compartments separated by a membrane. Rate of diffusion depends on the concentration difference between the area of high or low concentration (concentration gradient). Rate is faster if there is a bigger concentration gradient because the gradient contains potential energy: diffusion occurs until it reaches a state of equilibrium. Molecules still move, just maintain the gradient. Most stable, lowest energy state: simple diffusion: passive transport of substances across lipid portion of membranes with their concentration gradients. Large or charged molecules may be strongly impeded from crossing membranes.
