Key Terms
- 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 plasma membrane's cytoplasmic side and participates in the liquid uptake process 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 plasma membrane's inward-facing surface and assists in forming specialized structures, like coated pits, for phagocytosis
- concentration gradient
- area of high concentration adjacent to an area of low concentration
- diffusion
- passive transport process of low-molecular weight material according to its concentration gradient
- electrochemical gradient
- a combined electrical and chemical force that produces a 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 plasma membrane's structure 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 membrane lipids' hydrocarbon chains and often spans the membrane
- isotonic
- situation in which the extracellular fluid has the same osmolarity as the fluid inside the cell, resulting in no net water movement into or out of the cell
- osmolarity
- total amount of solutes dissolved in a specific amount of solution
- osmosis
- transport of water through a semipermeable membrane according to the water's concentration gradient 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 at the plasma membrane's surface 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 the cell membrane from the cell wall and constricting 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 plasma membrane's cytoplasmic side
- 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 using 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 results from primary active transport to the electrochemical gradient
- selectively permeable
- membrane characteristic that allows some substances through (also known as semipermeable)
- 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 a substance's passage across a membrane by binding it
- transporter
- specific carrier proteins or pumps that facilitate movement
- uniporter
- transporter that carries one specific ion or molecule