| A | B |
|---|
| Selective Permeability | Allowing some substance to cross it more easily than others |
| Amphipathic Molecule | Has both a hydrophobic and hydrophillic region |
| Fluid Mosaic Model | Model that shows the membrane is a fluid structure with various proteins embedded in or attached to a double layer of phospholipids |
| Integral Proteins | Proteins that penetrate the hydrophobic core of the lipid bilayer |
| Peripheral Proteins | Proteins that are not embedded in the lipid bilayer at all, loose appendages bound to surface |
| Transport Proteins | Transmembrane protein that helps a certain substance or class of closely related substances cross a membrane. |
| Diffusion | Tendency for molecules of any substance to spread out into the avaliable space. |
| Concentration Gradient | Substances diffuse down this, from where it is more concentrated to where it is less concentrated |
| Passive Transport | Diffusion of a substance across a biological membrane, cell does not expand energy to make it happen. |
| Hypertonic | Solution with higher concentration of solutes |
| Hypotonic | Solution with a lower concentration of solutes. |
| Isotonic | Solutions of equal solute concentration |
| Osmosis | Diffusion of water across a selectively permeable membrane |
| Osmoregulation | The control of water balance. |
| Turgid | Very firm, healthy state for plant cells |
| Flaccid | Limp, plant wilts, happens in an isotonic solution |
| Plasmolysis | A phenomenon in walled cells in which cytoplasm shrivels and the plasma membrane pulls away from the cell wall when the cell loses water to a hypertonic environment. |
| Facilitated Diffusion | When polar molecules and ions impeded by the lipid bilayer of the membrane diffuse passively with the help of transport proteins |
| Aquaporins | Water channel proteins |
| Gated Channels | A protein channel in a cell membrane that opens or closes in response to a particular stimulus |
| Active Transport | When cell pumps a molecule across a membrane against its gradient, cell must expend its own metabolic energy |
| Sodium-potassium Pump | Exchanges sodium for potassium across the plasma membrane of animal cells |
| Membrane Potential | Voltage across a membrane, ranges from about -50 to -200 millivolts |
| Electrochemical Gradient | Diffusion gradient of an ion, representing a type of potential energy that accounts for both the concentration difference of the ion across a membrane and its tendency to move relative to the membrane potential |
| Cotransport | A single ATP-powered pump that transports a specific solute can indirectly drive the active transport of several other solutes in this mechanism. |
| Exocytosis | Cellular excretion if macromolecules by the fusion of vesicles with the plasma membrane |
| Endocytosis | Cell takes in macromolecules and particulate matter by forming new vesicles from the plasma membrane. |
| Phagocytosis | A cell engulfs a particle by wrapping pseudopodia around it and packaging it within a membrane enclosed sac large enough to be called a vacuole. |
| Pinocytosis | Cell "gulps" droplets of extracellular fluid into tiny vesicles |
| Receptor-Mediated Endocytosis | Very specfic, movement of specific molecules into a cell by inward budding of membranous vesicles containing proteins with recepor sites specific to the molecules being taken in |
| Ligands | Extracellular substances that bind to receptors |
| Electrogenic Pump | Transport protein that generates voltage across a membrane |
| Proton Pump | Main electrogenic pump of plants, bacteria and funi, actively transports hydrogen ions (protons) out of the cell |
