Chapter 6: Cell Membranes Flashcards
Fluid Mosaic Model
General Structure of membranes
phospholipid bilayers
flexible, the interior is fluid, allows lateral movement of molecules
peripheral membrane proteins
lack exposed hydrophobic groups and so not penetrate the bilayer
integral membrane proteins
have hydrophobic and hydrophilic regions or domains. Some extend across the lipid bilayer; others are partially embedded.
transmembrane proteins
extend all the way through the phospholipid bilayer. they have one or more transmembrane domains
glycolipids
carbohydrate + lipid
glycoproteins
carbohydrate + protein; are involved in cell recognition and binding
tight junctions
help ensure directional movement of materials
desmosomes
like “spot welds”, small openings in the bilayer
gap junctions
allow cell communication
passive transport
no outside energy required (diffusion)
active transport
energy required
diffusion
the process of random movement towards equilibrium
equilibrium
particles continue to move, but there is no net change in distribution. net movement is directional until equilibrium is reached.
simple diffusion
small molecules pass through the lipid bilayer
osmosis
the diffusion of water
hypotonic
high solute concentration
isotonic
equal solute concentration
hypertonic
lower solute concentration
cannel proteins
have central pore lined w polar amino acids
carrier proteins
membrane proteins that bind substance and speed diffusions through the bilayer
ion channels
specific channel proteins w hydrophobic pores
gated
can be closed or open to ion passage
membrane potential
charge imbalance across a membrane, membrane potential is related to K+ concentration imbalance
facilitated diffusion
carrier proteins transport polar molecules across membranes
active transport
moves substance against a concentration and/or electrical gradient- requires ATP
primary active transport
requires ATP
Secondary Active Transport
energy comes from ion concentration gradient established but PAT (primary active transport)
sodium-potassium pump
PAT, an integral membrane glycoprotein (an anti porter)
endocytosis
brings larger molecules into a eukaryotic cell, forms a vesicle
phagocytosis
molecules entirely engulfed, white blood cells engulf foreign substance, phagosome forms, and fuses with lysosome
pinocytosis
vesicle forms to bring small dissolved substances or fluids into a cell.
receptor mediated endocytosis
depends on receptor proteins that bind to specific substances, sites are called coated pits
exocytosis
material in vesicle is expelled (reverse of endocytosis)
endothelial
capillary cells
