BISC 101 Lecture Notes - Lecture 1: Electrochemical Gradient, Facilitated Diffusion, Passive Transport

• School: Simon Fraser University
• Department: Biological Sciences
• Course: BISC 101
• Professor: Tony Williams

Document Summary

Tight junctions form watertight seals (epithelial cells) to minimize the possibility of leaks. Gap junctions provide cytoplasmic channels from one cell to another: key-concepts. Fluid mosaics of lipids and proteins; highly dynamic; results in selective permeability. Passive transport (diffusion, osmosis) down concentration gradient- no energy required. Facilitated diffusion is where transmembrane protein channels aid (speed up) passive transport. Active transport uses energy to move solutes against their (electro)chemical gradients (ion pumps, cotransporters) Bulk transport occurs via exocytosis and endocytosis: functions of membrane-asso(cid:272)iated protei(cid:374)s=(cid:863)(cid:373)osai(cid:272)(cid:863) part, transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment to the cytoskeleton and extracellular matrix (ecm, diffusion and osmosis. Small and uncharged molecules and hydrophobic compounds can cross membranes readily and spontaneously without expenditure of energy. Diffusion: solutes diffuse across the membrane each undergoes a net movement along its own concentration gradient. Allow ions and large polar solutes to diffuse rapidly down their concentration gradient.