BIO 201 Lecture Notes - Lecture 13: Membrane Lipids, Facilitated Diffusion, Direct Energy
6 Sep 2018
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Document Summary
Membrane permeability as a function of membrane lipids. Transmembrane transport: simple diffusion, facilitated diffusion, active transport. Protocells: fatty acid membranes saturated or unsaturated are most permeable. Mixed saturated and unsaturated are less permeable and saturated lipids are the least permeable. Indirect: energy from another compound moving down its concentration gradient. Simple diffusion high concentration to area of low concentration, i. e. (cid:862)down its concentration gradient. (cid:863). Water, oxygen, small molecules that can pass through the membrane. O2 and co2 diffuse down their concentration gradients. Not everything that we need can diffuse through the membrane. Molecule diffuses through a carrier protein down its concentration gradient. Facilitated diffusion: glucose glut1: extracellular glucose binds to glucose transporter (glut1, conformational change glut1 opens to interior of cell, glucose dissociates into cytoplasm, glut1 conformation reverts open to outside. Bidirectional: if [glucose] is very low in bloodstream, glucose can diffuse out through glut1. Typical ion concentration gradients must be transported up their concentration gradients.
