5.1: Key Terms

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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