Chapter 7

Question 1

Active Transport

Answer 1

The movement of a substance across a biological membrane against its concentration or electrochemical gradient

Question 2

Amphipathic Molecule

Answer 2

A molecule that has both a hydrophilic region and a hydrophobic region

Question 3

Aquaporins

Answer 3

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

Question 4

Concentration Gradient

Answer 4

An increase or decrease in the density of a chemical substance in an area

Question 5

Cotransport

Answer 5

The coupling of the “downhill” diffusion of one substance with the “uphill” transport against its own concentration gradient

Question 6

Diffusion

Answer 6

the process by which molecules move from an area of higher concentration to an area of lower concentration

Question 7

Electrochemical Gradient

Answer 7

The diffusion gradient of an ion, which is affected by both the concentration difference of the ion across a membrane (a chemical force) and the ion’s tendency to move relative to the membrane potential (an electrical force).

Question 8

Electrogenic Pump

Answer 8

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

Question 9

Endocytosis

Answer 9

the process by which a cell membrane surrounds a particle and encloses the particle in a vesicle to bring the particle into the cell

Question 10

Exocytosis

Answer 10

the process by which a substance is released from the cell through a vesicle that transports the substance to the cell surface and then fuses with the membrane to let the substance out

Question 11

Facilitated Diffusion

Answer 11

the transport of substances through a cell membrane along a concentration gradient with the aid of carrier proteins

Question 12

Flaccid

Answer 12

Limp. Lacking in stiffness or firmness, as in a plant cell in surroundings where there is no tendency for water to enter the cell.

Question 13

Fluid Mosaic Model

Answer 13

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

Question 14

Gated Channels

Answer 14

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

Question 15

Glycolipids

Answer 15

lipid substances with linked sugar groups that are key structural elements in cell membranes and precursors of other biologically active molecules important in cell signaling

Question 16

Glycoprotiens

Answer 16

Proteins that have carbohydrates covalently bonded to them.

Question 17

Hypertonic

Answer 17

when comparing two solutions, the solution with the greater concentration of solutes

Question 18

Hypotonic

Answer 18

when comparing two solutions, the solution with the lesser concentration of solutes

Question 19

Intergral Proteins

Answer 19

extend entirely through the membrane with both hydrophobic and hydrophilic ends (embedded)

Question 20

Ion Channels

Answer 20

a transmembrane protein channel that allows a specific ion to flow across the membrane down its concentration gradient

Question 21

Isotonic

Answer 21

having a solute concentration equal to that of another solution

Question 22

Ligands

Answer 22

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

Question 23

Membrane Potential

Answer 23

The charge difference between a cell’s cytoplasm and the extracellular fluid, due to the differential distribution of ions.

Question 24

Osmoregulation

Answer 24

The control of water balance in organisms living in hypertonic, hypotonic, or terrestrial environments.

Question 25

Osmosis

Answer 25

diffusion of molecules through a semipermeable membrane from a place of higher concentration to a place of lower concentration until the concentration on both sides is equal

Question 26

Passive Transport

Answer 26

The movement of substances across a cell membrane without the use of energy by the cell.

Question 27

Peripheral Proteins

Answer 27

Protein appendages loosely bound to the surface of the membrane and not embedded in the lipid bilayer.

Question 28

Plasmolysis

Answer 28

when a cell is in a hypertonic environment, the cell will lose water to its surroundings, shrink, and its plasma membrane will pull away from the wall

Question 29

Proton Pump

Answer 29

An active transport mechanism in cell membranes that consumes ATP to force hydrogen ions out of a cell and, in the process, generates a membrane potential

Question 30

Selective Permeability

Answer 30

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

Question 31

Sodium-potassium pump

Answer 31

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

Question 32

Tonicity

Answer 32

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

Question 33

Transport Proteins

Answer 33

protein molecules that help to transport substances throughout the body and across cell membranes

Question 34

Turgid

Answer 34

Firm. Walled cells become turgid as a result of the entry of water from a hypotonic environment.