4.1 - 4.3

Question 1

Molecules of substances within solids, liquids, and gases are in constant motion, and the source of energy causing this motion is ___.

Answer 1

heat

Question 2

Flux is defined as ___.

Answer 2

the amount of material moving in one direction between two compartments in a given period of time

Question 3

Which of the following would increase the time it takes for diffusion equilibrium to be reached between a cell’s intracellular fluid and the blood plasma?

Answer 3

Increasing the distance between the cell and the blood stream

Question 4

Fick’s first law of diffusion states that the rate of diffusion of a substance is proportional to its ___.

Answer 4

concentration gradient

Question 5

Diffusion of polar molecules into and out of cells and organelles is mainly limited by the ___.

Answer 5

lipid bilayer

Question 6

T/F: the energy for simple diffusion comes from ATP.

Answer 6

F

Question 7

To calculate the flux you would need to know the ___ of materials and the unit of time.

Answer 7

amount/quantity

Question 8

T/F: Diffusion equilibrium between two regions of a solution occurs more rapidly when there is a shorter distance between those regions.

Answer 8

T

Question 9

Nonpolar molecules diffuse much more rapidly across plasma membranes because these molecules can dissolve in the nonpolar regions of the membrane occupied by the fatty acid chains of the membrane’s ___.

Answer 9

phospholipids

Question 10

The mathematical formula for Fick’s first law of diffusion is ___.

Answer 10

J=PA(C_o-C_i)

Question 11

Ions are able to cross the cell membrane by ___.

Answer 11

moving through channel proteins

Question 12

The lipid bilayer functions as a barrier to the passage of ___-soluble molecules.

Answer 12

water

Question 13

The resting membrane potential is a result of the inside of a cell membrane having a slight net excess of ___ charges and the outside of a cell having a slight net excess of ___ charges.

Answer 13

negative; positive

Question 14

The ion’s electrochemical gradient results from the combination of a membrane ___ and a difference in ion ___ across a membrane.

Answer 14

potential; concentration

Question 15

The lipid bilayer is more permeable to which type(s) of molecule(s)? Select all that apply.

Answer 15

• lipid-soluble
• nonpolar
• hydrophobic

Question 16

Ion channels can usually be in one of two general states (not including inactivation): the ___ state or the ___ state.

Answer 16

closed; open

Question 17

Ions move across the cell membrane via ___.

Answer 17

integral membrane proteins

Question 18

Diffusion of polar molecules into and out of cells and organelles is mainly limited by the ___.

Answer 18

lipid bilayer

Question 19

Chemical messengers will bind to ___-gated ion channels on the target cell.

Answer 19

ligand

Question 20

The separation of the electrical charge that exists across plasma membranes of most cells is known as the membrane ___.

Answer 20

potential

Question 21

Which two factors directly determine the electrochemical gradient acting on a given ion across a cell membrane?

Answer 21

• the membrane potential

- the concentration gradient for the ion

Question 22

___ are ion channels that open or close in response to changes in the membrane potential.

Answer 22

voltage-gated channels

Question 23

When ion channels change between their open and closed states we can see changes in the membrane’s ___ to ion’s.

Answer 23

permeability

Question 24

The passage of amino acids and glucose and the nondiffusional movements of ions across cell membranes are mediated by integral membrane proteins known as ___.

Answer 24

transporters

Question 25

Which is TRUE about facilitated diffusion across a cell membrane?

Answer 25

The net transport by facilitated diffusion will be zero when concentrations of a substance are equal on the two sides of the membrane.

Question 26

This type of channel experiences a change in shape when a specific molecule binds to it.

Answer 26

Ligand-gated ion channel

Question 27

The difference in electrical charge between the inside and outside of a cell membrane is known as the ___.

Answer 27

membrane potential

Question 28

In active transport, the “active” refers to ___.

Answer 28

the use of energy to power the movement of molecules across a membrane

Question 29

When membrane potential changes cause movement of charged regions on channel proteins which alter the shape these channels are identified as ___-gated ion channels.

Answer 29

voltage

Question 30

Integral proteins tend to make excellent __.

Answer 30

transporters, because they span the plasma membrane

Question 31

Liver cells are able to break down glycogen into glucose, thus causing the intracellular glucose concentration to become higher than the extracellular glucose concentration. What happens to facilitated diffusion of glucose under these conditions?

Answer 31

Facilitated diffusion causes net movement of glucose out of the liver cells.

Question 32

A specific molecule which binds to a channel protein and either directly or indirectly causes changes to the channel’s shape is called a(n) ___.

Answer 32

ligand

Question 33

In an individual who is dehydrated, the numbers of aquaporins in the membranes of the kidney epithelial cells will ___; this will permit ___ water to move from the urine that is being formed in the kidney ducts back into the blood

Answer 33

increase; additional

Question 34

Be able to identify a picture of facilitated diffusion.

Answer 34

x

Question 35

A solute that cannot cross the cell membrane is called a(n) ___ solute.

Answer 35

nonpenetrating

Question 36

Active transport is characterized by ___.

Answer 36

• movement of molecules against their concentration gradient

- the requirement for energy

Question 37

T/F: The permeability of all cells to water is high and constant.

Answer 37

F (number of aquaporins differs in membranes, and in some can be altered by various signals)

Question 38

Which of the following act as transporters for nutrients to cross the plasma membrane?

Answer 38

integral proteins