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40 Cards in this Set

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active transport
Use of a plasma membrane carrier protein to move a molecule or ion from a region of lower concentration to one of higher concentration; it opposes equilibrium and requires energy.
adhesion junction
Junction between cells in which the adjacent plasma membranes do not touch but are held together by intercellular filaments attached to buttonlike thickenings.
anchoring junction
Junctions that mechanically attach adjoining cells (e.g., adhesion, tight, and gap junctions).
carrier protein
Protein that combines with and transports a molecule or ion across the plasma membrane.
cell recognition protein
Glycoprotein that helps the body defend itself against pathogens.
cell wall
Structure that surrounds a plant, protistan, fungal, or bacterial cell and maintains the cell's shape and rigidity.
channel protein
Protein that forms a channel to allow a particular molecule or ion to cross the plasma membrane.
cholesterol
One of the major lipids found in animal plasma membranes; makes the membrane impermeable to many molecules.
concentration gradient
Gradual change in chemical concentration from one point to another.
crenation
In animal cells, shriveling of the cell due to water leaving the cell when the environment is hypertonic.
desmosome
Intercellular junction that connects cytoskeletons of adjacent cells.
differentially permeable
Ability of plasma membranes to regulate the passage of substances into and out of the cell, allowing some to pass through and preventing the passage of others.
diffusion
Movement of molecules or ions from a region of higher to lower concentration; it requires no energy and tends to lead to an equal distribution.
endocytosis
Process by which substances are moved into the cell from the environment by phagocytosis (cellular eating) or pinocytosis (cellular drinking); includes receptor-mediated endocytosis.
enzymatic protein
Protein that catalyzes a specific reaction.
exocytosis
Process in which an intracellular vesicle fuses with the plasma membrane so that the vesicle's contents are released outside the cell.
facilitated transport
Passive transfer of a substance into or out of a cell along a concentration gradient by a process that requires a carrier.
fluid-mosaic model
Model for the plasma membrane based on the changing location and pattern of protein molecules in a fluid phospholipid bilayer.
gap junction
Junction between cells formed by the joining of two adjacent plasma membranes; it lends strength and allows ions, sugars, and small molecules to pass between cells.
glycolipid
Lipid in plasma membranes that bears a carbohydrate chain attached to a hydrophobic tail.
glycoprotein
Protein in plasma membranes that bears a carbohydrate chain.
hypertonic solution
Higher solute concentration (less water) than the cytoplasm of a cell; causes cell to lose water by osmosis.
hypotonic solution
Lower solute (more water) concentration than the cytoplasm of a cell; causes cell to gain water by osmosis.
isotonic solution
Solution that is equal in solute concentration to that of the cytoplasm of a cell; causes cell to neither lose nor gain water by osmosis.
osmosis
Diffusion of water through a differentially permeable membrane
osmotic pressure
Measure of the tendency of water to move across a differentially permeable membrane; visible as an increase in liquid on the side of the membrane with higher solute concentration.
phagocytosis
Process by which amoeboid-type cells engulf large substances, forming an intracellular vacuole.
phospholipid bilayer
Comprises the plasma membrane; each polar, hydrophilic head is bonded to two nonpolar, hydrophobic tails; contains embedded proteins.
pinocytosis
Process by which vesicle formation brings macromolecules into the cell.
plasmodesmata
In plants, cytoplasmic strands that extend through pores in the cell wall and connect the cytoplasm of two adjacent cells.
plasmolysis
Contraction of the cell contents due to the loss of water.
receptor-mediated endocytosis
Selective uptake of molecules into a cell by vacuole formation after they bind to specific receptor proteins in the plasma membrane.
receptor protein
Protein located in the plasma membrane or within the cell; binds to a substance that alters some metabolic aspect of the cell.
sodium-potassium pump
Carrier protein in the plasma membrane that moves sodium ions out of and potassium ions into animal cells; important in nerve and muscle cells.
solute
Substance that is dissolved in a solvent, forming a solution.
solution
Fluid (the solvent) that contains a dissolved solid (the solute).
solvent
Liquid portion of a solution that serves to dissolve a solute.
tight junction
Junction between cells when adjacent plasma membrane proteins join to form an impermeable barrier.
tonicity
Osmolarity of a solution compared to that of a cell. If the solution is isotonic to the cell, there is no net movement of water; if the solution is hypotonic, the cell gains water; and if the solution is hypertonic, the cell loses water.
turgor pressure
Pressure of the cell contents against the cell wall; in plant cells, determined by the water content of the vacuole and provides internal support.