Term | Definition |
active transport | method of transporting material that requires energy |
amphiphilic | molecule possessing a polar or charged area and a nonpolar or uncharged area capable
of interacting with both hydrophilic and hydrophobic environments |
antiporter | transporter that carries two ions or small molecules in different directions |
aquaporin | channel protein that allows water through the membrane at a very high rate |
carrier protein | membrane protein that moves a substance across the plasma membrane by changing
its own shape |
caveolin | protein that coats the cytoplasmic side of the plasma membrane and participates in the
process of liquid update by potocytosis |
channel protein | membrane protein that allows a substance to pass through its hollow core across
the plasma membrane |
clathrin | protein that coats the inward-facing surface of the plasma membrane and assists in the
formation of specialized structures, like coated pits, for phagocytosis |
concentration gradient | area of high concentration adjacent to an area of low concentration |
diffusion | passive process of transport of low-molecular weight material according to its
concentration gradient |
electrochemical gradient | gradient produced by the combined forces of an electrical gradient and
a chemical gradient |
electrogenic pump | pump that creates a charge imbalance |
endocytosis | type of active transport that moves substances, including fluids and particles, into a
cell |
exocytosis | process of passing bulk material out of a cell |
facilitated transport | process by which material moves down a concentration gradient (from high to
low concentration) using integral membrane proteins |
fluid mosaic model | describes the structure of the plasma membrane as a mosaic of components including phospholipids, cholesterol, proteins, glycoproteins, and glycolipids (sugar chains
attached to proteins or lipids, respectively), resulting in a fluid character (fluidity) |
glycolipid | combination of carbohydrates and lipids |
glycoprotein | combination of carbohydrates and proteins |
hydrophilic | molecule with the ability to bond with water; “water-loving” |
hydrophobic | molecule that does not have the ability to bond with water; “water-hating” |
hypertonic | situation in which extracellular fluid has a higher osmolarity than the fluid inside the
cell, resulting in water moving out of the cell |
hypotonic | situation in which extracellular fluid has a lower osmolarity than the fluid inside the cell,
resulting in water moving into the cell |
integral protein | protein integrated into the membrane structure that interacts extensively with the
hydrocarbon chains of membrane lipids and often spans the membrane; these proteins can be
removed only by the disruption of the membrane by detergents |
isotonic | situation in which the extracellular fluid has the same osmolarity as the fluid inside the cell,
resulting in no net movement of water into or out of the cell |
osmolarity | total amount of substances dissolved in a specific amount of solution |
osmosis | transport of water through a semipermeable membrane according to the concentration
gradient of water across the membrane that results from the presence of solute that cannot pass
through the membrane |
passive transport | method of transporting material through a membrane that does not require
energy |
peripheral protein | protein found at the surface of a plasma membrane either on its exterior or
interior side; these proteins can be removed (washed off of the membrane) by a high-salt wash |
pinocytosis | a variation of endocytosis that imports macromolecules that the cell needs from the
extracellular fluid |
plasmolysis | detaching of the cell membrane from the cell wall and constriction of the cell
membrane when a plant cell is in a hypertonic solution |
potocytosis | variation of pinocytosis that uses a different coating protein (caveolin) on the
cytoplasmic side of the plasma membrane |
primary active transport | active transport that moves ions or small molecules across a membrane
and may create a difference in charge across that membrane |
pump | active transport mechanism that works against electrochemical gradients |
receptor-mediated endocytosis | variation of endocytosis that involves the use of specific
binding proteins in the plasma membrane for specific molecules or particles, and clathrin-coated
pits that become clathrin-coated vesicles |
secondary active transport | movement of material that is due to the electrochemical gradient
established by primary active transport |
selectively permeable | characteristic of a membrane that allows some substances through but not
others |
solute | substance dissolved in a liquid to form a solution |
symporter | transporter that carries two different ions or small molecules, both in the same direction |
tonicity | amount of solute in a solution |
transport protein | membrane protein that facilitates passage of a substance across a membrane by
binding it |
transporter | specific carrier proteins or pumps that facilitate movement |
uniporter | transporter that carries one specific ion or molecule |