LO5 Flashcards
cell membranes are made of a
bilayer of phospholipids
model where bilayer of phospholipids are constantly in motion
fluid mosaic model
are self-sealing and fuse with other cell membranes
cell membranes
when the cell membrane spontaneously round up to form vesicles
self-sealing
fluidity buffer in animals
cholesterol
cholesterol at low temperatures
acts as a spacer between fatty acid tails
cholesterol restricts
van der walls interactions solidifying the membrane
cholesterol at high temperatures
keeps membranes stable by preventing phospholipids from moving to much
the ___ group of a cholesterol molecule interacts with the ___ head of a phospholipid to limit its movement
polar; polar
_____ proteins are firmly embedded in the lipid bilayer
integral
____ are at either surface of the bilayer
peripheral
integral proteins are
amphipathic
some proteins extend from
one side of a membrane to the other
short carbohydrate chains are often attached to what?
to the extracellular surface of membrane lipids and proteins
short carbohydrate chains form
glycolipids and glycoproteins
cell membranes are permeable to
small nonpolar and some small polar molecules
cell membranes are impermeable to
ions and larger polar molecules
membrane proteins are required to transport these molecules
impermeable ions and larger polar molecules
down their concentration gradient
higher to lower concentration
particles are uniformly distributed but continue to move
dynamic equillibrium
diffusion requires a
concentration gradient
a concentration gradient is a form of ______ energy
potential
osmosis is the _____ of water
diffusion
tendency of a solution to take in water by osmosis
osmotic pressure
high solute concentration = ____ effective water concentration = ____ osmotic pressure
low; high
when solutions have an equal solute concentration
isotonic
cells that have no net water movement
isotonic
has a higher solute concentration
hypertonic solution
cells will lose water and shrivel
hypertonic solution
_____ proteins form hydrophilic channels for ion and H2O transport
Channel
definition: if a cell wall is present (i.e. plant cell) the plasma membrane will shrink away from the cell wall
plasmolysis
cell will take up water and may burst
hypotonic
has a lower solute concentration
hypotonic
channel proteins that transport H2O across cell membranes
aquaporins
can be opened and closed in response to stimuli
ion channels that are gated
___ proteins undergo a conformational change as they transport specific solutes across a cell membrane
carrier
carrier proteins transport more ____ than channel proteins
slowly
active transport moves materials from ___ to ____ concentrations
low to high
_____________ pump transports Na and K ions against their gradient
sodium potassium
sodium-potassium pump establishes an ______ gradient
electrochemical
a ______ group from ATP is required for the pump to change shape
phosphate
ejects substances from cells
exocytosis
vesicle fuses with the plasma membrane and releases its contents outside the cell
exocytosis
uptakes molecules or small cells by surrounding them with plasma membrane
endocytosis
a ______ forms around the engulfed particles
vesicle
a cell ingests a large particle (bacteria, food)
phagocytocis
dissolved materials enter a cell enclosed in plasma membrane and gradually leak out
pinocytosis
in this form of endocytosis membrane proteins with specific receptors bind with specific molecules to bring them into a cell
receptor-mediated endoxytosis
______ is transported in the blood inside of LDL particles and is taken into cells via ____________
cholesterol, receptor mediated endocytosis
how is cholesterol transported inside blood
- LDL particles bind to specific receptors on plasma membrane
- receptors and LDL particles are taken into the cell in a vesicle
3&4. receptors are recycled back to the plasma membrane via a vesicle - LDL particles are degraded by lysosomes
membrane proteins from adjacent epithelial cells extend into the extracellular matrix and hold cells together
anchoring junctions
prevent the passage of materials through the extracellular spaces between epithelial cells
tight junctions
makes the lining of the intestines and blood-brain barrier
tight junctions
hold cells together and allow for the exchange of ions and small molecules
cell junctions
membrane proteins form channels between adjacent cells
gap junctions
this is in animals, cardiac muscles cells, some nerve cells
gap junctions
openings through the cell walls that connect the cytoplasms of adjacent plant cells
plasmodesmata
facilitated diffusion is a form of _____ transport
passive
concentration gradients are established by
active transport
concentration gradients require
energy to build
involve membrane proteins that may be linked to their cell’s cytoskeleton
cell junctions
