01:119:115 Lecture Notes - Lecture 6: Lipid Bilayer, Passive Transport, Transport Protein
27 Sep 2016
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Phospholipids spontaneously form closed bilayer vesicles a. ii. 1. b. due to roughly cylindrical shape strongly amphipathic nature: fluid-mosaic model b. i. Phospholipids can move laterally within 1 layer of the membrane b. ii. Fluidity depends on (fig 7. 5) (p. 127 evolution of difference in membrane fluidity) b. ii. 1. b. ii. 2. Passive cell does not expend metabolic energy a. ii. 1. a. a. ii. 1. a. i. Active cell expends metabolic energy: diffusion b. i. Tendency for molecules to spread out into available space b. iv. Atoms, molecules, and ions are in constant random motion b. iv. 1. They are evenly distributed in available space (fig 7. 10) b. v. net movement: down the concentration gradient b. v. 1. From region of initial high concentration to region of low concentration b. v. 2. Molecules are still moving, but no net change b. vi. Things that can diffuse across membrane by simple diffusion b. vi. 1. b. vi. 2. Small, nonpolar molecules they are hydrophobic b. vi. 2. a. Ex: hydrocarbons dissolve in the membrane and b. vi. 3. cross over. Even though they are polar, they can be small enough to pass through b. vi. 3. b.
