Key Terms

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Key Terms

Key Terms

active transport
a method of transporting material that requires energy
amphiphilic
a molecule that possesses a polar or charged area and a nonpolar or uncharged area, and is capable of interacting with both hydrophilic and hydrophobic environments
antiporter
a transporter that carries two ions or small molecules in different directions
aquaporin
a channel protein that allows water to pass through the membrane at a very high rate
carrier protein
a membrane protein that moves a substance across the plasma membrane by changing its own shape
caveolin
a protein that coats the cytoplasmic side of the plasma membrane and participates in the process of liquid uptake by potocytosis
channel protein
a membrane protein that allows a substance to pass through its hollow core across the plasma membrane
clathrin
a protein that coats the inward-facing surface of the plasma membrane and assists in the formation of specialized structures, such as coated pits, for phagocytosis
concentration gradient
an area of high concentration adjacent to an area of low concentration
diffusion
a passive process of the movement of low-molecular-weight material according to its concentration gradient
electrochemical gradient
a gradient produced by the combined forces of an electrical gradient and a chemical gradient
electrogenic pump
a pump that creates a charge imbalance
endocytosis
a type of active transport that moves substances, including fluids and particles, into a cell
exocytosis
a process of passing bulk material out of a cell
facilitated transport
a 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
a combination of carbohydrates and lipids
glycoprotein
a combination of carbohydrates and proteins
hydrophilic
a molecule with the ability to bond with water; (water-loving)
hydrophobic
a molecule that does not have the ability to bond with water; (water-hating)
hypertonic
a situation in which extracellular fluid has a higher osmolarity than the fluid inside the cell, resulting in water moving out of the cell
hypotonic
a situation in which extracellular fluid has a lower osmolarity than the fluid inside the cell, resulting in water moving into the cell
integral protein
a 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
a 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
the total amount of substances dissolved in a specific amount of solution
osmosis
the transport of water through a semipermeable membrane according to the concentration gradient of water across the membrane due to the presence of solute that cannot pass through the membrane
passive transport
a method of transporting material through a membrane that does not require energy
peripheral protein
a protein found at the surface of a plasma membrane on either its exterior or interior side; these proteins can be removed (washed off the membrane) by a high-salt wash
pinocytosis
a variation of endocytosis that imports macromolecules from the extracellular fluid that the cell needs
plasmolysis
the 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
a variation of pinocytosis that uses a different coating protein (caveolin) on the cytoplasmic side of the plasma membrane
primary active transport
the active transport that moves ions or small molecules across a membrane, and may create a difference in charge across that membrane
pump
the active transport mechanism that works against electrochemical gradients
receptor-mediated endocytosis
a 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
the movement of material that is due to the electrochemical gradient established by primary active transport
selectively permeable
a characteristic of a membrane that allows some substances through but not others
solute
a substance dissolved in a liquid that forms a solution
symporter
a transporter that carries two different ions or small molecules, both in the same direction
tonicity
the amount of solute in a solution
transport protein
a membrane protein that facilitates the passage of a substance across a membrane by binding to it
transporter
a specific carrier proteins or pumps that facilitate movement
uniporter
a transporter that carries one specific ion or molecule