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29 Cards in this Set
- Front
- Back
Selective permeability
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a key feature of plasma membranes;
allows some substances to cross a membrane more easily than others |
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Amphipathic
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contains both water-loving and water-fearing components
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Fluid mosaic model
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the current model used to describe the structure of membranes;
according to this model, the membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids |
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Integral proteins
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generally transmembrane proteins, with hydrophobic regions (stretches of nonpolar amino acids) that completely span the hydrophobic interior of the membrane
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Peripheral proteins
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proteins that are not embedded in the lipid bilayer at all;
loosely bound to the surface of the membrane, often to the exposed parts of integral proteins |
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Transport proteins
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integral proteins that selectively transport molecules across the membrane
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Diffusion
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the tendency for molecules of any substance to spread out into the available space;
a spontaneous process that decreases free energy |
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Concentration gradient
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in the absence of other forces, a substance will diffus efrom where it is more concentrated to where it is less concentrated (down its conc. gradient)
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Passive transport
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the diffusion of a substance across a biological membrane;
the cell does not have to expend energy to make this happen |
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Hypertonic
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when comparing two solutions of unequal solute concentration, refers to the solution with a higher conc. of solute
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Hypotonic
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when comparing two solutions of unequal solute concentration, refers to the solution with a lower conc. of solute
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Isotonic
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describes two solutions that are equal in solute conc.
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Osmosis
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a spcial case of active transport;
diffusion of water across a selectively permeable membrane |
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Osmoregulation
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the control of water balance
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Facilitated diffusion
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the spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their conc. gradients
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Gated channels
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proteins that respond to a stimulus by opening or closing;
stimulus may be electrical or chemical |
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Active tranpsort
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a process by which a cell moves a solute against its conc. gradient by expending its own energy
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Sodium-potassium pump
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a transport protein which exchanges sodium for potassium across the membrane of animal cells in order to maintain specific conc. of each within the cell;
the main electrogenic pump of animal cells |
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Membrane potential
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the voltage across a membrane;
reflects the separation of charges across a membrane |
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Electrochemical gradient
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the combination of the electrical gradient and the chemical gradient that drive the movement of ions across membranes
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Electrogenic pump
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a transport protein that generates voltage across a membrane, storing energy in the form of voltage
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Proton pump
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the main electrogenic pump plant, fungi, and bacteria cells;
actively transports hydrogen ions out of the cell |
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Cotransport
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a mechanism by which a single ATP-powered pump that transports a specific solute can indirectly drive the active transport of several other solutes
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Exocytosis
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a process by which cells secrete macromolecules by the fusion of vesicles with the plasma membrane
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Endocytosis
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a process by which cells take in macromolecules and particular matter by forming new vesicles from the plasma membrane
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Phagocytosis
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a process by which a cell engulfs a particle by wrapping pseudopodia around it and packaging it within a membrane enclosed sac; the sac then combines with a lysosome and the particle is digested
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Pinocytosis
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a process by which the cell "gulps" droplets of extracellular fluid in tiny vesicles
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Receptor-mediated endocytosis
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endocytosis that occurs when a specific molecule comes into to contact with specific membrane proteins
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Ligands
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a general term for any molecule that binds specifically to a receptor site of another molecule;
from the Latin "ligare" which means "to bind" |