BIO SCI 93 Lecture Notes - Lecture 7: Active Transport, Transport Direct, Sucrose

• School: UC-Irvine
• Department: Biological Sciences
• Course: BIO SCI 93
• Professor: Busciglio/ Wood/ Green

Document Summary

Amphipathic- has both a hydrophilic region and a hydrophobic region. Proteins can live in phospholipid bilayer with the hydrophilic regions protruding, maximizes contact of hydrophilic regions of proteins with water in cytosol and extracellular fluid. Allows hydrophobic parts a nonaqeuous environment as well. Membrane is held by hydrophobic interactions, is weaker than covalent bonds. Cholesterol seen as a (cid:862)fluidity buffer(cid:863)- makes membrane less fluid by restraining phospholipid movement at high temperatures and hinders close packing at low temperatures. Organisms able to change lipid composition of cell membranes to respond to changing temperature: unsaturated phospholipids increase in autumn for plants to keep membranes from solidifying. Integral proteins penetrate hydrophobic interior of lipid bilayer: transmembrane proteins- span membrane. Peripheral proteins- not embedded in lipid bilayer but are loosely bound to surface of membrane. Transport- provides hydrophilic channel that is selective for a specific solute. Can also shuttle substances by changing shape. Some hydrolyze atp to actively pump substances across membrane.