Biology - Chapter 7 Vocabulary

Front 1

selective permeability

Back 1

A property of biological membranes that allows them to regulate the passage of substances across them.

Front 2

amphipathic

Back 2

Having both a hydrophilic region and a hydrophobic region.

Front 3

fluid mosaic model

Back 3

The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids.

Front 4

integral proteins

Back 4

A transmembrane protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on one or both side of the membrane.

Front 5

peripheral proteins

Back 5

A protein loosely bound to the surface of a membrane or to part of a integral protein and not embedded in the lipid bilayer.

Front 6

glycoproteins

Back 6

A protein with one of more covalently attached carbohydrates.

Front 7

transport proteins

Back 7

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

Front 8

aquaporins

Back 8

A channel protein in a cellular membrane that specifically facilitates osmosis, the diffusion of free water across the membrane.

Front 9

diffusion

Back 9

The random thermal motion of particles of liquids, gases, or solids.

Front 10

concentration gradient

Back 10

A region along which the density of a chemical substance increases or decreases.

Front 11

passive transport

Back 11

The diffusion of a substance across a biological membrane with no expenditure of energy.

Front 12

osmosis

Back 12

The diffusion of free water across a selectively permeable membrane.

Front 13

tonicity

Back 13

The ability of a solution surrounding a cell to cause that cell to gain or lose water.

Front 14

isotonic

Back 14

Referring to a solution that, when surrounding a cell, causes no net movement of water into or out of the cell.

Front 15

hypertonic

Back 15

Referring to a solution that, when surrounding a cell, will cause the cell to lose water.

Front 16

hypotonic

Back 16

Referring to a solution that, when surrounding a cell, will cause the cell to take up water.

Front 17

osmoregulation

Back 17

Regulation of solute concentrations and water balance by a cell or organism.

Front 18

turgid

Back 18

Swollen or distended, as in plant cells.

Front 19

flaccid

Back 19

Limp, lacing turgor as in a plant cell in surroundings where there is a tendency for water to leave the cell.

Front 20

plasmolysis

Back 20

A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall.

Front 21

facilitated diffusion

Back 21

The passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure.

Front 22

ion channels

Back 22

A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.

Front 23

gated channels

Back 23

A transmembrane protein channel that opens or closes in response to a particular stimulus.

Front 24

active transport

Back 24

The movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins and requiring an expenditure of energy.

Front 25

membrane potential

Back 25

The difference in electrical charge across a cell's plasma membrane due to the differential distribution of ions.

Front 26

sodium-potassium pump

Back 26

A transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell.

Front 27

electrochemical gradient

Back 27

The diffusion gradient of an ion, which is affected by both the concentration difference of a ion across a membrane and the ion's tendency to move relative to the membrane potential.

Front 28

electrogenic pump

Back 28

An active transport protein that generates voltage across a membrane while pumping ions.

Front 29

proton pump

Back 29

An active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient, generating a membrane potential in the process.

Front 30

cotransport

Back 30

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

Front 31

exocytosis

Back 31

The cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane.

Front 32

endocytosis

Back 32

Cellular uptake of biological molecules and particulate matter via formation of vesicles from the plasma membrane.

Front 33

ligands

Back 33

A molecule that binds specifically to another molecule, usually a larger one.