Sections
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