Membrane Function Flashcards
what are the basic membrane functions?
- maintain internal cell environment at a steady state regardless of changes in the external environment
- acts a selective barrier regulating the movement of substances into and out of the cell
what are the 3 main types of transport?
passive
active
bulk membrane
what are the types of passive transport
simple duffusion
facilitated diffusion (channel, carrier)
osmosis
what is the type of active transport
pump
types of bulk membrane transport
- endosytosis
- exocytosis
diffusion
substance spreads out since molecules are constantly in motion and bumping into each other
passive transport definition
does not require energy and molecules move from high to low concentration
simple diffusion/transfer
movement accross a semi-permeable membrane, down a concetration gradient, no energy required, continues until equilibrium is achieved
what type of molecules go through simple diffusion?
O2 and CO2
facilitated transport
across a semi permeable membrane passive transport, continues until equilibrium is achieve, moves through a channel or carrier proteins
what types of particles go through channel proteins
small dissolved charged molecules like ions
aquaporins
a specific type of channel protein that facilitate the movement of water molecules across a membrane
carrier proteins
acts like turnstile/revolving door, underoges conformational change to allow molecules through
types of particles through carrier proteins
moves a variety of substnaces from charged particles to large uncharged molecules
uniport
movement of a single molecule in one direction - all channel proteins
symport
movement of 2 molecules in the same direction
antiport
movement of 2 molecules in opposite directions
osmosis
diffusion of water
describe osmosis
water moves from an area of high water concentration to an area of low water concentration
tonicity
the concentration of solutes in the environment surrounding the cell
isotonic
the same - equal movement in and out of cell
hypotonic
less concentration of solutes outside the cell
hypertonic
concentration of solutes is more outside the cell
osmotic lysis
animal cell bursts
hypertonic red blood cell
crenation
isotonic red blood cell
equilibrium
hypotonic red blood cell
hemolysis
plant cell in isotonic environment
flaccid - lacking firmness
(equilibrium)
water movement unable to provide cell with internal pressure necessary for structural support
plant cell in hypotonic environment
rigid cell wall prevents plant cell from rupturing
high presure to provide structural stability
turgor pressure
increrased internal pressure due to water entry provides structural support for plant
tugidity
cell swelling
plasmolysis
shrinking of plasma membrane and cytoplasm away from cell wall
plant cell in hypertonic environment
water moves out of cell, cell wall maintains its shape but cell membrane and cytoplasm shrinks
turgid plant
hypotonic solution
isotonic solution
flaccid
plasmolyzed
hypertonic solution
active transport
movement against concentration gradient - low to high
what does active transport require?
energy in the form of ATP and a transport protein called a pump
what does ATP do in active transport
indices a conformational change in the protein pump to allow specific molecules to enter/exit cell against its concentration gradient
what types of molecules does nulk membrane transport move?
transport of molecules in large quantity too large or too polar to pass through the membrane, onvolves the folding of the cell membrane to form a vesicle
types of endocytosis
pinocytosis
phagocytosis
receptor mediated endocytosis
phagocytosis
process by which living cells ingest other cells or large particles
when does phagocytosis happen
found in simpler forms of life for feeding (like amoebas) used in higher order organisms as a defense mecahnism against invasion by foreign particles
phagocyte
a white blood cell specialized for protecting the body by ingesting foreign substances
describe the mechanism of phagocytosis
- cell engulfs a particle by wrapping a psudopodia around it
- enclosed in a large enough sac to be classified as a vacuole called a phagosome
- hydrolytic enzymes in the lysosome digest the particle
- residual body contains indigestible material which is eventually discharged by exocytosis
lysosome
membrane bound sac of hydrolytic enzymes
what pH does the lysosome enzyme work at best?
at pH 5
how does the lysosome enzyme maindain acidic pH
pumps h+ into the lumen
lysosome function is phagocytosis
- fuse with food vacuole to digest food (like stomach in animals)
- fuses iwth phagosome to breakdown microorganisms
autophagy
lysosome recycles cell’s own organic material
pinocytosis
ingestion of dissolved materials - “cellular drinking”
cell folds inwards to take in fluild containing the desired substance
ingavinates
cell folds inwards to take in fluid
ligand
a molecule that binds to a receptor
receprot-mediated endocytosis
intake of molecules that bind specifically to a receptor on the surface of the cell
where are receptor proteins usually found?
clustered in regions of the membrane called coated pits which contain coat proteins that help form vesicles for endocytosis
describe the mechanism of receptor-mediated endocytosis
- ligands bind to receptor
- memrbane pinches to form vesicle
- ligand detaches from receptor
- vesicle pinch into 2 parts: free ligand and empty receptor
- ligands fuse with lysosome
- receptors returned to cell surface
exocytosis
movement of materials from the cell to the cell surface within membrane bound vesicles
how are the vesicles formed
off the golgi body of from endocytosis
exocytosis function
- secretion (release of waste, toxins, signaling molecules)
- recycling of membrane proteins
- restoring the cell memrbrane
