BIOMG 1350 Lecture Notes - Lecture 8: Electrochemical Gradient, Glucose Transporter, Active Transport

• School: Cornell University
• Department: Molecular Biology and Genetics
• Course: BIOMG 1350
• Professor: Huffaker

Document Summary

Transport proteins move water-soluble molecules across cell-membranes: small nonpolar molecules. Steroid hormones: small uncharged polar molecules. Ethanol glycerol: larger uncharged polar molecules. Membrane transport proteins fall into two classes: channels and transporters: channel. Flips between two conformations (facing inside and outside) Passive transport of uncharged molecules: uncharged molecules move down their concentration gradient, simple diffusion. High to low concentration: passive transport. Passive transport of charged molecules: voltage gradient=membrane potential. Move from + to : inside is more negative than outside, electrochemical gradient=concentration gradient + voltage gradient, (for an uncharged molecule, voltage gradient is irrelevant) Passive v. active transport: passive: no additional energy needed, down electrochemical gradient, active: needs energy, against electrochemical energy. Glucose transporter mediates passive movement: 1st conformation: extracellular space, 2nd conformation: intermediate, glucose is closed within, 3rd conformation: cytosolic space, moving randomly, whether or not glucose is present. 2nd could not have any glucose inside: permit passage of solute, but no role in determining direction.