Chapter 7: Membrane Structure and Function

Question 1

Selective Permeability

Answer 1

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

Question 2

Amphipathic

Answer 2

Having both a hydrophilic region and a hydrophobic region

Question 3

Fluid Mosaic Model

Answer 3

• Currently accepted model of cell membrane structure

- Envisions the membrane as a mosaic of protein molecules drifting laterally on a fluid bilateral of phospholipids

Question 4

Integral Protein

Answer 4

• Transmembrane protein
• Hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane
• Hydrophilic regions in contact with the aqueous solution on one or both sides of the membrane (or lining the channel in the case of a channel protein)

Question 5

Peripheral Protein

Answer 5

• A protein loosely bound to the surface of a membrane or to part of an integral protein
• Not embedded in the lipid bilayer

Question 6

Glycolipid

Answer 6

A lipid with one or more covalently attached carbohydrates

Question 7

Glycoprotein

Answer 7

A protein with one or more covalently attached carbohydrates

Question 8

Transport Protein

Answer 8

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

Question 9

Aquaporin

Answer 9

A channel protein in a cellular membrane that specifically facilitates osmosis

Question 10

Diffusion

Answer 10

• Random thermal motion of particles of liquids, gases, or solids in the presence of a concentration of an electrochemical gradient
• Results in the net movement of a substance from a region where it is more concentrated to where it is less concentrated

Question 11

Concentration Gradient

Answer 11

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

Question 12

Passive Transport

Answer 12

• Diffusion of a substance across a biological membrane

- No energy used

Question 13

Osmosis

Answer 13

The diffusion of free water across a selectively permeable membrane

Question 14

Tonicity

Answer 14

Ability of a solution surrounding a cell to cause that cell to gain or lose water

Question 15

Isotonic

Answer 15

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

Question 16

Hypertonic

Answer 16

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

Question 17

Hypotonic

Answer 17

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

Question 18

Osmoregulation

Answer 18

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

Question 19

Turgid

Answer 19

• Swollen or distended, as in plant cells

- A walled cell becomes this if it has a lower water potential than its surroundings, resulting in entry of water

Question 20

Flaccid

Answer 20

• limp or lacking turgor (stiffness or firmness)

- When a plant cell is in surroundings where there is a tendency for water to leave the cell

Question 21

Plasmolysis

Answer 21

• Phenomenon in walled cells where the cytoplasm shrivels and the plasma membrane pulls away from the cell wall
• Occurs when the cell loses water to a hypertonic environment

Question 22

Facilitated Diffusion

Answer 22

• Passage of molecules or ions down their electrochemical gradient across a biological membrane
• Specific transmembrane and transport proteins help
• Doesn’t require energy

Question 23

Ion Channel

Answer 23

Transmembrane protein channel that allows specific ion to diffuse across the membrane down its concentration or electrochemical gradient

Question 24

Gated Channel

Answer 24

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

Question 25

Active Transport

Answer 25

• Movement of a substance across a cell membrane against its concentration or electrochemical gradient
• Mediated by specific transport proteins
• Requires energy

Question 26

Sodium-Potassium Pump

Answer 26

• Transport protein in the plasma membrane of animal cells

- Actively transports sodium (Na) out of the cell and potassium (K) into the cell

Question 27

Membrane Potential

Answer 27

• Difference in electrical charge (voltage) across a cell’s plasma membrane due to the differential distribution of ions
• Affects the activity of excitable cells and the transmembrane movement of all charged substances

Question 28

Electrogenic Pump

Answer 28

Active transport protein that generates voltage across a membrane while pumping ions

Question 29

Electrochemical Gradient

Answer 29

• Diffusion gradient of an ion
• Affected by both the concentration difference of an ion across a membrane and the ion’s tendency to move relative to the the membrane potential (an electrical force)

Question 30

Proton Pump

Answer 30

• Active transport protein in a cell membrane
• Uses ATP to transport hydrogen ions out of a cell against their concentration gradient
• Generates a membrane potential

Question 31

Cotransport

Answer 31

Coupling of the “downhill” diffusion of one substance to the “uphill” transport of another against its own concentration gradient

Question 32

Exocytosis

Answer 32

Cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane

Question 33

Endocytosis

Answer 33

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