Chapter 5: Membranes Flashcards
transmembrane proteins
span or traverse the membrane from one leaflet to the other
lipid-anchored proteins
proteins that associate with a membrane because they have a lipid molecule that is covalently attached to an amino acid side chain in the protein
peripheral membrane proteins
non covalently bound to regions of a transmembrane protein
fluidity of bilayers
lateral, or rotational movement (two-dimensional)
flip-flop (flippase)
Shorter tails = more fluid
Presence of double bonds (unsaturated) = more fluid
Cholesterol @ higher temps = less fluid
Cholesterol @ lower temps = more fluid and prevents freezing
simple difussion
substance moves from a region of high concentration to a region of lower concentration (down a concentration gradient)
facilitated difussion
transmembrane protein provides a passageway for a substance to diffuse across a membrane
active transport
moves a substance from a region of low concentration to one of higher concentration (agasint a concentration gradient)
uses energy
isotonic
when the concentrations of solutes on both sides of the plasma membrane are equal
hypertonic
when the concerntration of solutes outside the cell is higher than the inside
hypotonic
when the concentration of solutes outide the cell is lower than the inside
osmosis
water moves across the membrane from the hypotonic compartment into the hypertonic
osmotic lysis
when placed in hypotonic solution, the cell may take up too much water and rupture
plant cells prevent osmotic lysis because of cell walls
plasmolysis
cell membrane shrinks due to lack of water when in a hypotonic solution
channels
open passageways that facilitate the difussion of ions or molecules across a membrane
rapid movement
gated
ligands
uniporters
bind a single ion or molecule and transport it across the membrane
