Biological Membranes Flashcards
integral membrane protein
proteins that interact with the hydrophobic core or the phospholipid bilayer
- transmembrane proteins span the entire bilayer while monotopic proteins only protrude into the hydrophobic core from one side
- segments inserted in the membrane contain hydrophobic side chains
peripheral membrane protein
loosely bound to either side of the membrane (?) by weak interactions with lipids or other proteins
glycoprotein
a carbohydrate chain in the aqueous environment that is covalently attached to a membrane protein
glycolipid
a carbohydrate chain in the aqueous environment that is covalently attached to a lipid in the membrane
selectively permeable
only allowing certain materials to enter or exit the cell
active transport
movement of materials across a membrane that requires added energy
active transport
movement of materials across a membrane against their concentration gradient
requires energy input in the form of ATP or a concentration gradient
diffusion
passive movement of molecules into a cell, down their concentration gradient
simple (passive) diffusion
movement of non-polar and small polar molecules between the hydrophobic lipid tails of the bilayer
-occurs by dissipation of concentration gradient and requires no energy input
facilitated diffusion
movement of large polar and charged molecules across a membrane through specialized integral proteins
channel protein
transmembrane protein, open hydrophilic channel that allow facilitated diffusion of specific molecules
Ka+ channel
Na+ channel
aquaporin (H20 channel)
carrier protein
transmembrane protein, remain open to extracellular side of membrane until desired molecule binds, at which point it changes shape to release said molecule into the cytoplasm of the cell (a form of facilitated diffusion)
osmosis
passive movement of water across a selectively permeable membrane to equilibrate the concentration of a solute on either side
hypertonic
the concentration of solute is higher in the surrounding solution than inside of the cell (water will exit/flow out, causing the cell to become plasmolyzed or shrivel)
hypotonic
the concentration of solute is higher inside the cell than in the surrounding solution (water will flow into the cell, causing it to swell and become turgid, or potentially lyse if the cell has no wall)
isotonic
movement of water in and out of the cell is equal, which is ideal for cells without cells walls, but cells with cell walls become flaccid due to a lack of turgor pressure
contractile vacuole
large, membrane bounded sac in the cytoplasm that contracts to expel excess water from the cell
electrochemical gradient
the combination of a concentration gradient and a membrane potential created when an electrogenic pump moves ions across a membrane against their concentration gradient
membrane potential
voltage or flow or charge through a membrane due to a separation of charge across the membrane
electrogenic pump
protein that hydrolyzes ATP in order to pump ions into and out of the cell across their concentration gradient
eg. Na+/K+ pump
co-transport
protein that uses the energy from an accumulated electrochemical gradient to bring other molecules into the cell against their concentration gradient (couples the facilitated diffusion of an ion with the active transport of another molecule)
eg. H+/sucrose co-transporter
exocytosis
vesicles from inside the cell fuse with the membrane to secrete proteins and other molecules
phagocytosis
cells engulf other cells using pseudopodium
vacuole formed as the membrane of the cell encloses the smaller cell it will “eat”
pinocytosis
cell non-specifically engulfs extracellular fluid, which may contain liquids, ions, small macromolecules, etc
receptor-mediated endocytosis
used for uptake of high concentration of a specific ligand (solute)
-integral receptor proteins bind to specific ligands and cause the formation of a vesicle
bulk transport
transport of a large amount of molecules into or out of the cell at once
-relies on vesicles
