Exam 3: Ch 10 Biomembrane Structure Flashcards
membrane transport proteins
enable ions, sugars, aa and vitamins to cross the semi permeable phospholipid bilayer
receptors
proteins in the cell membrane that allow the cell to recognize chemical signals to adjust metabolism or gene expression
cytoskeleton
a network of protein filaments in the cytosol
provide mechanical support for shape and cell movement
fluid mosaic model
individual lipids can move horizontally in the membrane and spin in place (but not flip orientation)
membrane fluidity
noncovalent van der waals interactions
most common phospholipid in membranes
phosphoglycerides
amphipathic membrane structure
fatty acid hydrophobic hydrocarbon tails
polar hydrophilic heads
3 types of membrane lipid
phospholipids
sphingolipids
sterols
amphipathic things spontaneously form…
micelles
liposomes
membrane bilayers
artificial membranes lack _____
proteins
lipid raft
less fluid patches of membrane
more cholesterol (stability)
contain plasma membrane proteins involved in transmitting extracellular signals to the inside
sphingolipids have different head groups than phospholipids
phosphotidylinositol
signaling molecule
DIAG - diacyl glycerol triphosphate
why dont cells fall apart if the membrane is so fluid?
cell walls (plants/bacteria)
ECM
cholesterol
type of structure formed by pure phospholipids depends on…
length of tails
degree of saturation
temperature
leaflet
half of the phospholipid bilayer
phosphatidylcholine
type of phosphoglyceride
most abundant phospholipid in membrane
choline polar head group (OH + phosphate)
phospholipases
enzymes that celave ester bonds
produce lysophospholipids (only 1 acyl tail) that are signaling molecules
recognized by receptors and affect physical properties of the memb.
plasmalogens
ether linkage - greater chemical stability
human brain and heart
structure of sterols
4 rings
cholesterol has an OH on one ring
effect of sterols on membranes
structural support
prevent extremely tight packing to allow more fluidity
fluorescence recovery after photobleaching (FRAP)
phospholipids with a fluorescent substituent are used to monitor lipid movement
shows lateral movement of proteins and lipids
do sphingomyelins form more gel-like and thicker bilayers than phosphoglycerides?
yes
bilayers made of cylindrical lipids (long tails and large head groups) are ____, while bilayers made from cone lipids (small head groups) are ______
flat, curved
flippase
ATP powered transport proteins
flip exoplasmic lipids (phospholipids) from cytosolic leaflet to exoplasmic leaflet where they function
ex. phosphatidylserine flipped to exoplasmic side where it activates enzymes involved in blood clotting
lipid droplet
vesicles made of triglycerides and cholesterol esters that originate from the ER and serve as lipid storage
extracellular domain functions
bind extracellular molecules like signaling proteins, ions, and small metabolites
intramembrane domain functions
form channels/pores
organize membrane proteins into larger assemblies
intramembrane domain functions
anchoring cytoskeletal proteins to the membrane to trigger intracellular signaling pathways
organizing membrane proteins into larger assemblies
integral membrane proteins (transmembrane)
span the bilayers and have 3 domains (cytosolic, exoplasmic, transmembrane)
can be attached to ECM
transmembrane domain made of alpha helices and beta sheets
lipid-anchored membrane proteins
bound covalently to 1+ lipid molecules
hydrophobic domain embedded in one leaflet and serves as the anchor
peripheral membrane proteins
bound to the memb. indirectly by interactions w/ integral or lipid-anchored memb. proteins or directly by interactions w/ head groups
can be attached to ECM too
single-pass transmembrane protein
has only 1 membrane spanning alpha helix
ex. Glycophorin A
multipass transmembrane protein
an important group has 7 membrane spanning alpha helices
ex. G protein-coupled cell-surface receptors (bacteriorhodopsin)
aquaporin
highly conserved proteins that transport water, glycerol, and other hydrophilic molecules
multipass (6 alpha helices) tetramers of 4 identical subunits
ex. glycerol channel Glpf
aquaporin 0
most abundant protein in the plasma membrane of fiber cells in the lens of the eye
annular phospholipids - form a tight ring
multiple beta strands in _____ form membrane spanning barrels
porins
hydrophilic interior and hydrophobic exterior
2 examples of lipid-anchored membrane proteins
Ras (GTPase superfamily)
Rab (GTPase superfamily)
orientation of transmembrane glycoproteins/glycolipids
carbohydrate chains in exoplasmic domain
makes them available to interact with ECM, lectins, growth factors, and Ab
proteins can be removed from membranes by ______ or high-____ solutions
detergents, high-salt solutions
detergent
amphipathic molecules that disrupt membranes by intercalating into them
ex. bile salts, SDS
critical micelle concentration (CMC)
concentration of detergent at which micelles form
