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34 Cards in this Set

  • Front
  • Back
Has both a hydrophilic and a hyrdophobic region
Amphipathic Molecule
Membrane is a fluid structure with various proteins embedded or attatched to the phospholipid bilayers
Fluid mosaic model
Stabilizes the cell membrane in it's fluidity
Steroid cholesterol
Penetrate hydrophobic core of the lipid bilayer
Integral proteins
Appendages loosely bound to the surface of the membrane - exposed parts of integral proteins
Peripheral proteins
Ogliosaccharides covalently bonded to lipids - markers that distinguish from one cell to another
Lets hydrophilic substances pass through the lipid bilayer to avoid contact; spans the membrane; some have a hydrophilic channel, others hold onto the passengers and move them across
Transport Proteins
Tendency for molecules to spread out into the available space - thermal energy absorbed from environment
In the absence of other forces, a substance will diffuse to where it is less concentrated - spontaneous process because it decreases free energy
Concentration Gradient
Diffusion of a substance across a biological membrane - does not have to expend energy to make it happen
Passive Transport
Solution with a higher concentration of solutes
Solution with a lower solute concentration
Solutions of equal solute concentration
Diffusion of water across a selectively permeable membrane - a special case of passive transport
The control of water balance; animals and other organisms have rigid cell walls have this adaptation
Elastic plant cell wall is very firm; healthy state for most plant cells
Limp; plant cells and their surroundings are isotonic - no tendency for water to enter - causes plant to wilt
Plasma membrane pulls away from the wall - usually lethal
Polar molecules and ions impeded by the lipid bilayer of the membrane diffuse passively with the help of transport proteins that span the membrane
Facilitated diffusion
Water channel proteins; facilitates the massive amounts of diffusion
Stimulus causes them to open or close - chemical - a substance other than the one to be transported
Gated channels
Pumping a molecule across a membrane against its gradient - must expend metabolic energy
Active transport
Exchanges sodium for potassium across the plasma membrane of animal cells
Sodium-potassium pumps
Voltage across a membrane - -50 to -200 millivolts
Membrane potential
A chemical force and an electrical force drive the diffusion of ions across a membrane acting on an ion - resulting voltage used to do work
Electrochemcal gradient
Transport protein that generates voltage across a membrane - against concentration gradient - can be a chemical or an electrical gradient
Electrogenic pump
Actively transports hydrogen ions (protons) out of the cell - more acidic outside - rush back through contrasport protein
Proton pump
Single ATP-powered pump that transports a specific solution can indirectly drive the active transport of several other solutes in a mechanism
Fusion of vesicles with the plasma membrane
Cell takes in macromolecules and particulate matter by forming new vesicles from the plasma membrane
Cell engulfs a particle by wrapping pseduopodia around it and packing it within a membrane - enclosed sac large enough to be classified as a vacuole
Cell "gulps" droplets of extracelluluar fluid into tiny vesicles
Specific receptor sites exposed to extracellular fluid - triggers vesicle formulation by ligands
Receptor-mediated Endocytosis
Any molecule that binds specifically to a receptor site of another molecule