cell membrane quick flashcards

what does compartmentalization allow for

allows for efficiency and specialization of function

what is the plasma membrane

separates living cell from external environment

response

what is the plasma membrane made of

made of a phospholipid bilyaer

phospholipids are amphipathic molecules - hydrophobic tails, hydrophilic tails

what are integral proteins

stably attached to the biological membrane

span the phospholipid bilayer

what are peripheral proteins

temporarily adhered to the biological membrane

either attached to an integral protein or penetrating peripheral regions of the bilayer

what is the fluid mosaic model of the plasma membrane

phospholipids in plasma membrane move

most lipids and some proteins drift laterally

why must membranes be semipermeable

to be sufficiently compact: avoid uncontrolled trafficking

to be sufficiently fluid: remain biologically active

what do usnaturated hydrocarbon lipid tails allow for

allows the membrane to remain fluid at low temperatures

what does cholesterol allow for

prevents membranes from solidifying in low temperatures

prevents membranes becoming too fluid in high temperatures

what are membrane transport proteins

allow passage of select solutes across membrane

some transport proteins shuttle substances across membrane through a change in shape

may provide hydrophilic channel

what does passive transport involve

small, non polar molecules

slow

what is diffusion

movement of molecules across a membrane from region of high to low concentration

what is facilitated diffusion

involves charged hydrophilic solutes

polar molecules enter cell at high rates

ion channels and gated channels

no ATP required

what is osmosis

movement of water molecules from a region of high to low concentration across a semi permeable membrane

what is the tonicity of a solution

its ability to move water in/out of a cell through osmosis

what is an isotonic solution

does not move water

eg cells without cell wall are healthy in this

what is a hypotonic solution

moves water in (less concentrated solutes)

eg cells with a cell wall are healthy in this

what is a hypertonic solution

moves water out (more concentrated solutes)

what do channel proteins allow for

water or specific hydrophilic molecules to pass through:

in both directions

down their gradient

what are gated channels

open in response to an electrical or chemical stimulus

what are aquaporins

selectively conduct water in/out, preventing passage of charged species

what is active transport

requires ATP & is against the gradient

eg Na+/K+ pump

what is the Na+/K+ pump

Shape of pump has affinity for Na+, 3 Na+ ions bind → phosphorylation causes the shape to change and Na+ is released outside

Shape of pump now has affinity for K+, 2 K+ bind → loss of phosphate group causes pump to go back to original shape and K+ is released

what is exocytosis

large molecules are secreted when a vesicle fuses with the plasma membrane

transport from the cell

what is endocytosis

large molecules are taken in when plasma membrane pinches inward

transport to the cell

what is bulk transport

moves large molecules

requires energy

what is phagocytosis

ingestion of solid food particles (engulfed bacteria, virus, debris)

what is pinocytosis

ingestion of fluids containing small solutes (ie vitamins, toxins)

what is rec-mediated

small/macro molecules bind to receptors before being engulfed

what are membrane enzyme proteins

lowers activation energy of reaction, making it faster

when substrate binds, enzymes undergo a conformation shift which makes them more reactive

high specificity to substrates (lock and key)

why are membrane enzyme proteins membrane bound?

allows precise position, orientation and proximity with other enzymes

catalyse reactions in specific locations

coordinated catalysis in metabolic pathways

what are membrane receptor proteins

the external signaling molecule may cause a shape change of the receptor protein, passing a message into the cell

has a binding site with a specific shape that fits a molecule

what does cell to cell recognition involve

glycoproteins:

serve as identification tags

recognised by membrane proteins of other cells

short lived interactions

what does intercellular joining involve

tight junctions, desmosomes, gap junctions:

neighbouring cells in tissues, organs or organ systems often adhere, interact and communicate through direct physical contact

what does attachment to cytoskeleton and ECM involve

integrins:

bind ECM and cytoskeleton

important during development for cell migration

can coordinate cellular changes in response to environmental signals