Ap Bio Ch. 7

Front 1

selectively permeability

Back 1

a property of biological membranes that allows some substances to cross more easily than others

Front 2

amphipathic molecule

Back 2

a mole-ecule that has both a hydrophilic region and hydrophobic region

Front 3

fluid mosaic model

Back 3

the currently accepted model of cell membrane as a mosaic of individual protein molecules drifting laterally in a fluid bilayer of phospholipids

Front 4

integral proteins

Back 4

typically a transmembrane protein with hydrophobic regions that completely spans the hydrophobic interior of the membrane

Front 5

peripheral proteins

Back 5

a protein appendage loosely bound to the surface of a membrane and not embedded in the lipid bilayer

Front 6

glycolipids

Back 6

a lipid covalently attached to a carbohydrate

Front 7

glycoproteins

Back 7

a protein covalently attached toa a carbohydrate

Front 8

transport proteins

Back 8

a transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane

Front 9

aquaporins

Back 9

a transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane (osmosis)

Front 10

diffusion

Back 10

the spontaneous tendency of a substance to move down its concentration gradients from a more concentrated to a less concentrated area

Front 11

concentration gradient

Back 11

an increase or decrease in the density of a chemical substance in an area. cells often maintain concentration gradients of ions across their membranes. When a gradient exists, the ions or other chemical substances involved tend to move from where they are more concentrated to where they are less concentrated.

Front 12

passive transport

Back 12

the diffusion of a substance across a biological membrane

Front 13

osmosis

Back 13

the diffusion of water across a selectively permeable membrane

Front 14

tonicity

Back 14

the ability of a solution to cause a cell within it to gain or lose water

Front 15

isotonic

Back 15

having the same solute concentration as another solution

Front 16

hypertonic

Back 16

in comparing two solutions, referring to the one with greater solute concentration

Front 17

hypotonic

Back 17

in comparing two solutions, referring to the one with a lower solute concentration

Front 18

osmoregulation

Back 18

how organisms regulate solute concentrations and balance the gain and loss of water

Front 19

turgid

Back 19

very firm. a walled cell becomes turgrid if it has a greater solute concentration than its surroundings, resulting in entry of water

Front 20

flaccid

Back 20

limp. a walled cell is flaccid in surroundings where there is no tendency for water to enter

Front 21

plasmolysis

Back 21

a phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall when the cell loses water to a hypertonic environment

Front 22

facilitated diffusion

Back 22

the spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients

Front 23

ion channels

Back 23

protein channel in a cell membrane that allows passage of a specific ion down its concentration gradient

Front 24

gated channels

Back 24

a protein channel in a cell membrane that opens or closes in response to a particular stimulus

Front 25

active transport

Back 25

the movement of a substance across a biological membrane agains its concentration or electrochemical gradient with the help of energy input and specific transport proteins

Front 26

sodium-potassium pump

Back 26

a special transport protein in the plasma membrane of animal cells that transportts sodium out of the cell and potassium into the cell against their concentration gradients

Front 27

membrane potential

Back 27

the charge difference between a cell's cytoplasm and the extracellular fluid, due to the differential distribution of ions. membrane potential affects the activity of excitable cells and transmembrane movement of all charged substances

Front 28

electrochemical gradient

Back 28

the diffusion gradient of an ion, representing a type of potential energy that accounts for both the concentration difference of theion across a membrane and its tendency to move relative to the membrane potential

Front 29

electrogenic pump

Back 29

an ion transport protein that generates voltage across a membrane

Front 30

proton pump

Back 30

an active transport mechanism in cell membranes that uses ATP to force hydrogen ions out of a cell, generating a membrane potential in the process

Front 31

cotransport

Back 31

the coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient

Front 32

exocytosis

Back 32

the cellular secretion of macromolecules by the fusion of vesicles with the plasma membrane

Front 33

endocytosis

Back 33

the cellular uptake of macromolecules and particulate substances by localized regions of the plasma membrane that surround the substance and pinch off to form an intracellular vesicle

Front 34

ligands

Back 34

a molecule that binds specifically to a receptor site of another molecule

Front 35

phagocytosis

Back 35

a type of endocytosis involving large, particulate substances, accomplished mainly by macrophages, neutophils, and dendritic cells

Front 36

pinocytosis

Back 36

a type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes

Front 37

receptor-mediated endocytosis

Back 37

the movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with recpetor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances

Front 38

cotransport

Back 38

the coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient

Front 39

exocytosis

Back 39

the cellular secretion of macromolecules by the fusion of vesicles with the plasma membrane

Front 40

endocytosis

Back 40

the cellular uptake of macromolecules and particulate substances by localized regions of the plasma membrane that surround the substance and pinch off to form an intracellular vesicle

Front 41

ligands

Back 41

a molecule that binds specifically to a receptor site of another molecule

Front 42

phagocytosis

Back 42

a type of endocytosis involving large, particulate substances, accomplished mainly by macrophages, neutophils, and dendritic cells

Front 43

pinocytosis

Back 43

a type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes

Front 44

receptor-mediated endocytosis

Back 44

the movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with recpetor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances