Chapter 4/Movement of Molecules Across Cell Membranes

Question 1

Movement of molecules from one location to
another as a result of their random thermal
motion

Answer 1

Diffusion

Question 2

Magnitude of net flux influenced by:

Answer 2

-Temperature
– Mass of the solute
– Surface area
– Medium

Question 3

Diffusion time _ in proportion to the _ of the distance over which the
molecules diffuse

Answer 3

increases , square

Question 4

Limited _
* Diffusion is _over a long distance

Answer 4

not effective, distance

Question 5

Membranes considerably slow the diffusion of
molecules

Answer 5

across their surfaces

Question 6

O2, CO2, fatty acids, steroid hormones
rapidly through membranes.

Answer 6

diffuse

Question 7

Polar molecules __readily through
membranes.

Answer 7

do not, diffuse

Question 8

Ions (Na+, K+, Cl–, Ca2+) use __ to diffuse in and out of the ;\;’

Answer 8

protein channels, cell

Question 9

channels form

Answer 9

integral membrane protein

Question 10

Specificity of channel is determined by .

Answer 10

pore
size, charge, and binding sites

Question 11

Separation of electrical charges across the
plasma membrane

Answer 11

Membrane potential

Question 12

Diffusion of ions influenced by

Answer 12

concentration
and membrane potential

Question 13

Channels are regulating

Answer 13

to control movement
of ions in and out of the cell

Question 14

Type of gated channels

Answer 14

-Ligand-gated
– Voltage-gated
– Mechanically gated

Question 15

Molecules that are too large and charged

Answer 15

Mediated Transport Systems

Question 16

Protein transporters bring these molecules

Answer 16

into and out of the cell

Question 17

Magnitude of net flux influenced by

Answer 17

-Solute concentration
– Affinity of transporters for solute
– Number of transporters
– Rate of conformational change

Question 18

Facilitated diffusion

Answer 18

-Net flux from high to low concentration
– Uses transporter to move solute across membrane

Question 19

-Uses energy
– Moves solute against the concentration gradient

Answer 19

Active transport

Question 20

ATPase: hydrolysis of ATP

Answer 20

Use ATP directly

Question 21

-Found in every cell
– Helps establish and maintain membrane potential

Answer 21

Na+/K+-ATPase

Question 22

Use electrochemical gradient across
membrane as energy source

Answer 22

Secondary Active Transport

Question 23

• Ion
  – Cotransported molecule

Answer 23

Two binding sites

Question 24

move
molecules in same
direction

Answer 24

Cotransporters

Question 25

move molecules in
opposite directions

Answer 25

counter transporter

Question 26

Net diffusion of water across a membrane

Answer 26

Osmosis

Question 27

Facilitated by aquaporins

Answer 27

Osmosis

Question 29

of aquaporins varies among cell types

Answer 29

Osmosis

Question 30

The total solute concentration of a solution

Answer 30

Osmolarity

Question 31

1 osmol = 1 mol of solute particles

Answer 31

Osmolarity

Question 32

Higher osmolarity means lower water
concentration

Answer 32

Osmolarity

Question 33

Movement of molecules into the cell via
vesicles

Answer 33

Endocytosis

Question 34

3 general types: endocytosis

Answer 34

-Pinocytosis
– Phagocytosis
– Receptor mediated endocytosis

Question 35

Movement of molecules out of the cell via
vesicles

Answer 35

exocytosis

Question 36

Replace portions of the plasma membrane that
endocytosis removed
– Add new membrane components to plasma
membrane
– Provides a pathway for secretion of membrane-
impermeable molecules

Answer 36

exocytosis

Question 37

diffusion between
adjacent cells.
– Limited by tight junctions

Answer 37

Paracellular pathway

Question 38

movement through the
cell

Answer 38

Transcellular pathway