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38 Cards in this Set
- Front
- Back
the movement of materials across a membrane through the use of cellular energy, normally against a concentration gradient.
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active transport
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a channel selective for water formed by proteins that span the cell membrane.
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aquaporin
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a membrane protein that facilitates the diffusion of specific substances across the membrane. The molecule to be transported binds to the outer surface of the carrier protein; the protein then changes shape, allowing the molecule to move across the membrane through the protein.
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carrier protein
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a membrane protein that forms a channel or pore completely through the membrane and that is usually permeable to one or to a few water-soluble molecules, especially ions.
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channel protein
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anchor cell membranes
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attachment proteins
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the number of particles of a dissolved substance in a given unit of volume.
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concentration
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the difference in concentration of a substance between two parts of a fluid or across a barrier such as a membrane.
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concentration gradient
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a strong cell-to-cell junction that attaches adjacent cells to one another.
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desmosome
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the net movement of particles from a region of high concentration of that particle to a region of low concentration, driven by the concentration gradient; may occur entirely within a fluid or across a barrier such as a membrane.
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diffusion
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the process in which the plasma membrane engulfs extracellular material, forming membrane-bound sacs that enter the cytoplasm and thereby move material into the cell.
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endocytosis
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a protein catalyst that speeds up the rate of specific biological reactions.
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enzyme
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the process in which intracellular material is enclosed within a membrane-bound sac that moves to the plasma membrane and fuses with it, releasing the material outside the cell.
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exocytosis
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the diffusion of molecules across a membrane, assisted by protein pores or carriers embedded in the membrane.
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facilitated diffusion
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a liquid or gas.
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fluid
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a model of membrane structure; according to this model, membranes are composed of a double layer of phospholipids in which various proteins are embedded. The phospholipid bilayer is a somewhat fluid matrix that allows the movement of proteins within it.
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fluid mosaic model
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a type of cell-to-cell junction in animals in which channels connect the cytoplasm of adjacent cells.
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gap junction
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a protein to which a carbohydrate is attached.
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glycoprotein
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a difference in concentration, pressure, or electrical charge between two regions.
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gradient
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referring to a solution that has a higher concentration of dissolved particles (and therefore a lower concentration of free water) than has the cytoplasm of a cell.
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hypertonic
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referring to a solution that has a lower concentration of dissolved particles (and therefore a higher concentration of free water) than has the cytoplasm of a cell.
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hypotonic
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referring to a solution that has the same concentration of dissolved particles (and therefore the same concentration of free water) as has the cytoplasm of a cell.
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isotonic
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the diffusion of water across a differentially permeable membrane, normally down a concentration gradient of free water molecules. Water moves into the solution that has a lower concentration of free water from a solution with the higher concentration of free water.
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osmosis
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the movement of materials across a membrane down a gradient of concentration, pressure, or electrical charge without using cellular energy.
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passive transport
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a type of endocytosis in which extensions of a plasma membrane engulf extracellular particles and transport them into the interior of the cell.
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phagocytosis
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a double layer of phospholipids that forms the basis of all cellular membranes. The phospholipid heads, which are hydrophilic, face the water of extracellular fluid or the cytoplasm; the tails, which are hydrophobic, are buried in the middle of the bilayer.
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phospholipid bilayer
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the nonselective movement of extracellular fluid, enclosed within a vesicle formed from the plasma membrane, into a cell.
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pinocytosis
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a cell-to-cell junction in plants that connects the cytoplasm of adjacent cells.
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plasmodesma
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the process by which reduced water pressure in the central vacuole of a plant cell allows the cytoplasm to shrink away from the cell wall. Plasmolysis causes soft parts of plants to wilt.
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plasmolysis
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the selective uptake of molecules from the extracellular fluid by binding to a receptor located at a coated pit on the plasma membrane and pinching off the coated pit into a vesicle that moves into the cytoplasm.
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receptor-mediated endocytosis
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a protein, located on a membrane (or in the cytoplasm), that recognizes and binds to specific molecules. Binding by receptor proteins typically triggers a response by a cell, such as endocytosis, increased metabolic rate, or cell division.
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receptor protein
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a protein or glycoprotein protruding from the outside surface of a plasma membrane that identifies a cell as belonging to a particular species, to a specific individual of that species, and in many cases to one specific organ within the individual.
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recognition protein
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the quality of a membrane that allows certain molecules or ions to move through it more readily than others.
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selectively permeable
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the diffusion of water, dissolved gases, or lipid-soluble molecules through the phospholipid bilayer of a cellular membrane.
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simple diffusion
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a substance that is dissolved in a solvent
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solute
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a liquid capable of dissolving (uniformly dispersing) other substances in itself.
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solvent
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a type of cell-to-cell junction in animals that prevents the movement of materials through the spaces between cells.
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tight junction
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a protein that regulates the movement of water-soluble molecules through the plasma membrane.
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transport protein
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pressure developed within a cell (especially the central vacuole of plant cells) as a result of osmotic water entry.
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turgor pressure
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