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Chapter 8: Membrane Structure & Function
Campbell Chapter 8- Membranes
31
Biology
11th Grade
11/28/2010

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Term
selective permeability
Definition
allows some substances to enter while preventing others from entering
Term
amphipathic
Definition
having both a hydrophobic and hydrophilic side
Term
fluid mosaic model
Definition
name given to the plasma membrane due to the many protein molecules bobbing in a double layer of phospholipids
Term
integral protein
Definition
transmembrane proteins with hydrophobic regions that completely span the membrane
Term
peripheral proteins
Definition
proteins not embedded inthe lipid bilayer, but are loosely bound to the surface of the membrane often to the exposed part of integral proteins
Term
transport protein
Definition
integral protein that allows passage of ions and polar molecules into and out of the cell
Term
diffusion
Definition
tendancy of molecules to spread out into the available space in an attempt to reach equilibrium
Term
concentration gradient
Definition
areas were there is a difference in concentration from one area to the next
Term
passive transport
Definition
transport that requires no energy expenditure (osmosis, facilitated diffusion, simple diffusion)
Term
hypertonic
Definition
higher solute concentration
Term
hypotonic
Definition
lower solute concentration
Term
isotonic
Definition
equal solute concentration
Term
osmosis
Definition
passive transport of water across a membrane
Term
osmoregulation
Definition
control of water balance of animals without cell walls as their internal solute concentration attempts to equalize with the external environment's solute concentration
Term
turgid
Definition
very firm plant cell
Term
flaccid
Definition
limp plant cell (wilting)
Term
plasmolysis
Definition
losing water to the surroundings, shriveling of cells
Term
facilitated diffusion
Definition
polar molecules and ions getting assistance to cross the plasma membrane by way of an integral protein
Term
active transport
Definition
passage of particles across the membrane that requires energy
Term
sodium potassium pump
Definition
type of active transport that exchanges Na+ ions for K+ ions across an animal membrane
Term
membrane potential
Definition
voltage across a cell membrane (-50 to -200 mV)
Term
electrochemical gradient
Definition
diffusion gradient of an ion
Term
electrogenic pump
Definition
transport protein that generates voltage across a membrane
Term
proton pump
Definition
main electrogenic pump of plants, bacteria, and fungi. Actively transports H+ ions out of the cells
Term
cotranport
Definition
the coupling of the downhill diffusion of one substance to the uphill tranport of another against its concentration gradient
Term
exocytosis
Definition
fusion of vesicles with the plasma membrane resulting in the secretion of materials outside the cell
Term
endocytosis
Definition
cells taking in macromolecules by forming new vesicles from the plasma membrane
Term
phagocytosis
Definition
cellular eating-engulfing a large particle of food
Term
pinocytosis
Definition
cell gulping of droplets of extracellular fluid in tiny vesicles
Term
receptor mediated endocytosis
Definition
protein receptors embedded in the p. membrane bind molecules and then form vesicles to bring them into the cell
Term
ligand
Definition
extracellular substances that bind to receptors on the plasma membrane
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