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 uptake 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
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