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29 Cards in this Set

  • Front
  • Back
Selective permeability
a key feature of plasma membranes;
allows some substances to cross a membrane more easily than others
contains both water-loving and water-fearing components
Fluid mosaic model
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
Integral proteins
generally transmembrane proteins, with hydrophobic regions (stretches of nonpolar amino acids) that completely span the hydrophobic interior of the membrane
Peripheral proteins
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
Transport proteins
integral proteins that selectively transport molecules across the membrane
the tendency for molecules of any substance to spread out into the available space;
a spontaneous process that decreases free energy
Concentration gradient
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)
Passive transport
the diffusion of a substance across a biological membrane;
the cell does not have to expend energy to make this happen
when comparing two solutions of unequal solute concentration, refers to the solution with a higher conc. of solute
when comparing two solutions of unequal solute concentration, refers to the solution with a lower conc. of solute
describes two solutions that are equal in solute conc.
a spcial case of active transport;
diffusion of water across a selectively permeable membrane
the control of water balance
Facilitated diffusion
the spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their conc. gradients
Gated channels
proteins that respond to a stimulus by opening or closing;
stimulus may be electrical or chemical
Active tranpsort
a process by which a cell moves a solute against its conc. gradient by expending its own energy
Sodium-potassium pump
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
Membrane potential
the voltage across a membrane;
reflects the separation of charges across a membrane
Electrochemical gradient
the combination of the electrical gradient and the chemical gradient that drive the movement of ions across membranes
Electrogenic pump
a transport protein that generates voltage across a membrane, storing energy in the form of voltage
Proton pump
the main electrogenic pump plant, fungi, and bacteria cells;
actively transports hydrogen ions out of the cell
a mechanism by which a single ATP-powered pump that transports a specific solute can indirectly drive the active transport of several other solutes
a process by which cells secrete macromolecules by the fusion of vesicles with the plasma membrane
a process by which cells take in macromolecules and particular matter by forming new vesicles from the plasma membrane
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
a process by which the cell "gulps" droplets of extracellular fluid in tiny vesicles
Receptor-mediated endocytosis
endocytosis that occurs when a specific molecule comes into to contact with specific membrane proteins
a general term for any molecule that binds specifically to a receptor site of another molecule;
from the Latin "ligare" which means "to bind"