Lecture 4: Cell Membrane Flashcards
basic function of the cell membrane
to separate the outer and inner cell environments
to separate two aqueous compartments
phospholipid structure/formation
formed from a neutral fat in which one of the groups of the fat is replaced by a phosphate group
each P has 2 amino acid tails associated with it
hydrophilic head
phosphate groups
hydrophobic tails
amino acid tails, 2 per head
bilayer composition
two phospholipids that are arranged with tails on the inside
singer and nicholson
fluid mosaic model of cell membrane
backed up by freeze-fracture technique
outer leaflet
cholesterol phosphatidylcholine, -ethanolamine sphingomyelin glycolipids GPI
what does GPI stand for? significance?
glycosylphosphatidylinositol
important in cell signaling
GPI anchoring proteins for peripheral proteins
inner leaflet
cholesterol
phosphatidylethanolamine, -serine, -inositol
located on inner and outer leaflet
cholesterol
cholesterol functions
moderates membrane fluidity
functions in changing tempertures
cholesterol at high temperatures
interferes with FA chain mvt
makes outer less fluid
reduces permeability to small molecules
cholesterol at low temperatures
prevents membrane from freezing
maintains fluidity
location of glycolipids
outer leaflet only
function of glycolipids
function to create a cell coat --- involved in cell to cell interactions conveys antigenicity
what portion of a glycolipid faces the extracellular matrix?
the carbohydrate portion
what are lipid rafts composed of?
cholesterol and sphingolipids
function of lipid rafts
to compartmentalize cellular processes by serving as organization center
examples:
assemble cell signaling molecules
influence membrane fluidity – cholesterol
protein and neurotransmitter trafficking
____ proteins will cluster in lipid rafts.
GPI-anchoring proteins
tips of microvilli
glycocalyx
functions of glycocalyx
protect cell from ionic/mechanical stress
barrier against microorganisms
involved in cell-cell interactions
mechanisms for moving materials across cell membranes
diffusion
osmosis
facilitated diffusion
active transport
mvt of particles based upon a concentration gradient
diffusion
diffusion of water across a semipermeable membrane
osmosis
diffusion that requires transport molecules
facilitated diffusion
mvt of particles against a gradient
active transport
categories of transport proteins
Unitransporters = uniporters co-transporters = symporters counter-transporters = antiporters
difference between symporters and antiporters
carry 2 molecules in same or opposite directions
