Chapter 7

Question 1

Aquaporin

Answer 1

A membrane protein that enables water molecules to pass through the membrane.

Question 2

Amphipathic

Answer 2

Has both a hydrophilic region and a hydrophobic region

Question 3

Fluid mosaic model

Answer 3

The membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids.

Question 4

A membrane is held together primarily by ____

Answer 4

Hydrophobic interactions

Question 5

The membrane remains fluid to a lower temperature if it is rich in phospholipids with ….

Answer 5

Unsaturated hydrocarbon tails.

Question 6

Cholesterol can be thought of as a…

Answer 6

Fluidity buffer for the membrane because it resists changes in membrane fluidity that can be caused by changes in the temperature.

Question 7

Like a tile mosaic, a membrane is…

Answer 7

A collage of different proteins, often clustered together in groups, embedded in the fluid matrix of the lipid bilayer.

Question 8

Proteins determine most of the membrane’s functions.

Answer 8

True

Question 9

Integral proteins

Answer 9

Penetrate the hydrophobic interior of the lipid bilayer. Transmembrane proteins span through the entire membrane.

Question 10

The hydrophobic interior of an integral protein consists of…

Answer 10

Non polar amino acids usually coiled into alpha helices

Question 11

Peripheral proteins

Answer 11

Are not embedded in the lipid bilayer at all; they are appendages loosely bound to the surface of the membrane, often to exposed parts of integral proteins.

Question 12

Six major functions performed by proteins of the plasma membrane

Answer 12

Transport
Enzymatic activity
Signal transduction
Cell-cell recognition
Intercellular joining
Attachment to the cytoskeleton and ECM

Question 13

How membrane sidedness arises:

Answer 13

The asymmetrical arrangement of proteins, lipids, and their associated carbohydrates in the plasma membrane is determined as the membrane is being built by the ER and Golgi apparatus.

Question 14

What molecules can cross the lipid bilayer of the membrane easily?

Answer 14

Non-polar, hydrophobic, molecules

Question 15

The hydrophobic interior of the membrane impedes direct passage through the membrane of….

Answer 15

Ions and polar molecules, which are hydrophilic

Question 16

Channel proteins

Answer 16

-Transport proteins
Have a hydrophilic channel
Ex. Aquaporins

Question 17

Carrier proteins

Answer 17

-Transport protein
Hold onto their passengers and change shape in a way that shuttles them across the membrane.

Question 18

The concentration gradient itself represents ___________ and drives diffusion

Answer 18

Potential energy

Question 19

Tonicity

Answer 19

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

Question 20

Non penetrating solutes

Answer 20

Concentration of solutes that cannot cross the membrane.

Question 21

If there is a higher concentration of non-penetrating solutes in the surrounding solution,

Answer 21

Water will tend to leave the cell, and vice versa

Question 22

In a solution that is hypertonic to the cell,
Hypertonic means

Answer 22

More non-penetrating solutes
-the cell will lose water

Question 23

A solution that is hypotonic to the cell means

Answer 23

Less non-penetrating solutes
-Water will enter the cell

Question 24

A cell without rigid cell walls can tolerate…

Answer 24

Neither excessive uptake nor excessive loss of water

Question 25

Osmoregulation

Answer 25

The control of solute concentrations and water balance.

Question 26

Cell wall helps maintain water balance

Answer 26

True

Question 27

Healthy state for most plant cells:

Answer 27

Turgid in a hypotonic solution

Question 28

Ion channels

Answer 28

Channel proteins that transport ions

Question 29

Many ion channels function as ________

Answer 29

Gated channels

Question 30

Gated channels

Answer 30

Open or close in response to a stimulus

Question 31

Facilitated diffusion is considered passive transport because the solute is moving down its concentration gradient, a process that requires no energy.

Answer 31

True

Question 32

The transport proteins that move solutes against their concentration gradients are all _________

Answer 32

Carrier proteins

Question 33

Sodium-potassium pump

Answer 33

Exchanges Na+ for K+ across the plasma membrane of animal cells.

Question 34

All cells have voltages across their plasma membrane

Answer 34

True

Question 35

Voltage

Answer 35

Electric potential energy

Question 36

Membrane potential

Answer 36

The voltage across a membrane Ranges from about -50 to -200 millivolts (mV)

Question 37

The cytoplasmic side of the membrane is negative in charge relative to the extracellular side

Answer 37

True

Question 38

The membrane potential favors the passive transport of cations into the cell and anions out of the cell because the inside of the cell is negative compared with the outside

Answer 38

True

Question 39

Two forces drive the diffusion of ions across a membrane

Answer 39

A chemical force (the ion’s concentration gradient) An electrical force (the effect of the membrane potential on the ion’s movement)

Question 40

Electrochemical gradient

Answer 40

The combination of forces acting on an ion

Question 41

An ion diffuses down its …

Answer 41

Electrochemical gradient

Question 42

Electrogenic pump

Answer 42

A transport protein that generates voltage across a membrane

Question 43

Proton pump

Answer 43

-electrogenic pump Actively transports protons (H+) out of the cell.

Question 44

Exocytosis

Answer 44

The process where the cell secretes certain molecules by the fusion of vesicles with the plasma membrane

Question 45

In endocytosis,

Answer 45

The cell takes in molecules and particulate matter by forming new vesicles from the plasma membrane.

Question 46

Three types of endocytosis

Answer 46

Phagocytosis Pinocytosis Receptor-mediated endocytosis

Question 47

Ligands

Answer 47

A term for any molecule that binds specifically to a receptor site on another molecule