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39 terms

Chapter 5 (Membrane)

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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 adjacent plasma membranes do not touch but are held together by intercellular filaments attacked to buttonlike thickenings.
aquaporin
channel protein through which water can diffuse across a membrane
bulk transport
movement of elements in an organism in large amount
carrier protein
protein that combines with a molecule or ion to transport it across the plasma membrane
cell recognition protein
glycoprotein that helps the body recognize when it is being invaded by pathogens so that an immune response can occur
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
a steroid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids.
concentration gradient
difference in the number of molecules or ions of any one substance between two adjoining regions
crenation
in animal cell, shriveling of the cell due to water leaving the cell when the environment is hypertonic
desmosome
intercellular junction that connects cytoskeletons of adjacent cells; fastens cells together as strong sheets
differentially permeable
ability of 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
net movement of like ions or molecules from a region where they are most concentrated to an adjoining region where they are less concentrated; they move down their concentration gradient and use no energy
endocytosis
cell uptake of substances by forming vesicles from patches of plasma membrane. three modes: receptor-mediated endocytosis, phagocytosis, and pinocytosis (cell drinking)
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
extracellular matrix
nonliving substance in which animal cells are imbeded; is composed of protein and polysaccharides
facilitated transport
passive transfer of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients. moves from high to low concentration.
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 through cells
glycolipid
lipid in plasma membranes covalently bonded to a carbohydrate
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
hyopotonic 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
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
substances can travel between cells this way
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Plasmodesmata.gif
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
cotransporter that, when energized, actively transports sodium out of a cell and helps potassium passively diffuse into it at the same time
tight junction
junction between cells when adjacent plasma membrane proteins join to form an impermeable barrier
tonicity
the ability of a solution to cause a cell within it to gain or lose water
turgor pressure
pressure of the cell's contents against the cell wall; in plant cells, determined by the water content of the vacuole and provides internal support
junction protein
protein that assists cell-to-cell communication at the plasma membrane