Functional organization of the cell Flashcards
why can deteregents dissolve phospholipid membranes
detergents are water soluble at much higher or lower [ ] than phospholipids
bc they are amphipathic
much higher [ ]
lateral diffusion can proceed rapidly at high temp (what state)
sol state
low temp PLs diffuse slowly (what state)
gel state
temp at which the bilayer converts from gel to sol phase is what
transition temp (TT)
PL w long saturated FA have high or low TT
high TT
what based phospholipids are the most common membrane lipids (so which one is less common)
glycerol based phospholipids
(sphingosine-based lipids are less common)
cholesterol increases or reduces membrane fluidity and how
cholesterol reduces membrane fluidity making it more rigid
rigid steroid rings bind to and partially immobilize FA side chains
phospholipid bilayer are impermeable to what and permeable to what
impermeable to charged and large water-soluble molecules
permeable to small uncharged polar molecules
phospholipid composition is not identical
surface facing cytoplasm (inner) contains what
outward surface is composed of almost exclusively what
surface facing the cytoplasm (inner) contains phosphatidylethanolamine and phosphatidylserine
outward facing surface composed of phosphatidylcholine
integral protein vs peripheral proteins
peripheral - adhere tightly to the cytoplasmic or surface of plasma membrane
integral - embedded WITHIN the membrane or attached by covalent bonds
transmembrane protein
proteins that span the entire plasma membrane
the membrane spanning portions of transmembrane proteins and usually what helices
hydrophobic alpha-helices
integral proteins can serve as (5)
-receptors
-adhesion molecules
-transporters
-enzymes
-signal transduction components
integral proteins can serve as recptors that transmit signals between what
the cell and its environment
what are integrins and 2 examples
cell-matrix ADHESION molecules that link cells to components of the extracellular matrix (fibronectin, lamin)
cadherins
Ca-dependent adhesion molecules
N-CAM
Ca-INDEPENDENT neural cell adhesion molecules
nucleolus
transcription of rRNA and assembly of ribosomal subunits
nuclear lamina
fibrillar protein skeleton that provides structural support to the nuclear envelope
(proteins known as lamins)
rough ER function
-synthesis of secretory and membrane proteins
-undergo post-translational modification and folding in lumen of rER
if a protein is misfolded or unassembled, it is tagged w what in the rER and sent to where for degradation
tagged w ubiquitin
sent to proteasome
rER constitutive pathway vs regulated
constitutive - secretion is continious and unregulated (membrane p)
regulated - secretion is directed by hormonal or neural signals (secreted p)
smooth ER helps w what synthesis and stores what
lipid synthesis
stores calcium
golgi
precessing station for proteins and targets newly formed proteins to the appropriate subcellular area
mitochondria surface of inner membrane consists of folds called what
cristae
lysosome
breaks down cellular debris
acidic environment
materials taken by endocytosis fuses w lysosomes
epithelial cells
separate te internal milieu from external milieu
apical membrane vs basolateral membrane of epithelial cells
apical membrane - face lumen, often topologically continuous w outside world
basolateral - indirectly makes contact w blood and rest on a basement membrane
tight junction
impedes passage of molecules and ions
(CLAUDINS/transmembrane proteins)
adhering junction
belt that encircles an entire epitherlial cell just below the level of the tight junction
provide clues about the nature and PROXIMITY of their neighbors
(CADHERINS, ACTIN FILLAMENTS)
desmosomes
holds adjacent cells together tightly at a single round spot
(CADHERINS, PLAQUE, INTERMEDIATE FILAMENTS)
gap junction
channels that interconnect cytosol of neighboring cells (allow small molecules to diffuse freely)
(CONNEXONS)
