AP Bio Unit 4 - Cell Membrane Structure + Transport

what is the most abundant lipid in the cell membrane?

phosphoilipid

amphipathic

has a hydrophilic and hydrophobic region

examples of amphipathic molecules in the cell membrane

proteins, phospholipids

describe the “fluid mosaic model”

used to describe the cell membrane; phospholipid bilayer is fluid, membrane contains a mosaic of proteins

why is the membrane so fluid?

weak hydrophobic attractions hold the bilayer together

what happens to the membrane as temperature decreases?

remains fluid until it solidifies

effect of membranes with unsaturated phospholipids as temp. decreases

remain fluid b/c kinks in the unsaturated fatty acid prevent phospholipids from packing closely together

describe cholesterol’s effect on the membrane.

at high temperatures, reduces fluidity by limiting phospholipid movement. at low temps, prevents membrane from solidifying by preventing phospholipids from packing closely together. as a whole, helps membrane resist fluidity changes

two classes of membrane proteins

integral and peripheral

location of integral proteins

penetrate the bilayer; most are transmembrane and traverse the entire membrane while others extend partway through

location of peripheral proteins

loosely bound to exposed parts of integral proteins and rarely to the membrane surface

six functions of the membrane

transport (channel, active transport), enzymatic activity, signal transduction, cell-cell recognition, intercellular joining (in junctions like gap and tight), attachment to the cytoskeleton or ECM

structure of glycoproteins

carbohydrates covalently bonded to proteins

structure of glycolipids

carbohydrates covalently bonded to lipids

function of glycoproteins/glycolipids

serve as markers that help cells distinguish and recognize each other

pathway of membrane component synthesis

produced in the ER → transported to the Golgi via vesicle → transported to the plasma membrane via vesicle