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
symporters
bind two or more ions or molecules and transport them in the same direction
ampiporters
bind two or more ions or molecules and transport them in opposite directions
primary active transport
pump
ATP
secondary active transport
use of pre-exisiting gradient to drive another solute
Na+/K+ -ATPase
active transporter (ampiporter)
gap junctions
small gaps between the plasma membrane of cells
connexion (6 connexin proteins)
too small for passage of RNA, proteins and polyssacharides
plasmodesmata
ducts or intercellular channels between plasma membranes in plant cells
macromolecules do pass
exocytosis
material inside the cell is packaged into vessels and excreted
endocytosis
plasma membrane invaginates to form a vesicle and bring substances in
receptor-mediated
pinocytosis
phagocytosis (only phagocytes)
anchoring junctions
junctions that occur between adjacent cells and the ECM
adherens junctions
connect cells to each other via cadherins
actin filaments
desmosomes
connect cells to each other via cadherins
intermediate filaments
hemidesmosomes
connect cells to the EMC via integrins
intermediate filaments
focal adhesions
connect cells to the EMC via integrins
actin filaments
cell adhesion molecules (CAMs)
cadherins: cell-cell
integrins: cell-CAM
abnormalities: metastasis of cancer
tight junctions
forms a tight seal between adjacent cells, preventing leakage between the cells
occludin
claudin
