3: the plasma membrane and membrane potential Flashcards
functions of the plasma membrane
mechanical barrier
selectivity
maintains differences in ion concentrations
characteristics of the lipid bilayer
forms the basic structure of the membrane
hydrophobic interior is a barrier to passage of water soluble substances between the ECF and ICF
responsible for the fluidity of the membrane
fluid mosaic model
refers to membrane fluidity and pattern of proteins embedded in the membrane
phospholipids
phosphate head (- charge)
3 fatty acid chain tail (no charge)
proteins
allow charged molecules into the cell through protein channels
cholesterol
contributes to the fluidity and stability of the membrane
carbohydrates
allow for recognition/signal to other cells
leak channels
always open and permit passage of their selected ion
gated channels
can be opened or closed (voltage gated+mechanically gated)
agonist gated
has specific binding site, chemical must bind for it to be opened
carrier molecules
transfer specific substances across the membrane that are unable to cross on their own
cell adhesion molecules
bind cell to cell, and help keep internal cell fibers in the correct location
desmosomes
physically extend intracellular filaments to connect cell membranes
tight junctions
allow nothing to pass between them and have highly selective barriers
gap junctions
a gap exists between adjacent cells. linked by small tunnels called connexons
passive vs active transport
does not require ATP, requires ATP
diffusion
solute will travel to a less concentrated area of the solution
osmosis
the net diffusion of water down its concentration gradient through a selectively permeable membrane
osmotic pressure
the tendency for osmotic flow of water into a solution
facilitated diffusion
carrier mediated transport
primary active transport
energy in the form of ATP is required for the carrier to change shape and alternately expose the carrier’s binding sites for ion to opposite sides of the membrane
secondary active transport
the carrier does not split the atp to move a substance against its concentration gradient
endocytosis
the plasma membrane surrounds the substance to be ingested, pinching off a membrane enclosed vesicle so the engulfed material is trapped within the cell
exocytosis
a membrane enclosed vesicle formed within the cell fuses with the plasma membrane, then opens up and releases its contents to the exterior
