Ch 4

Question 1

T/F: The plasma membrane is permeable to any type of molecule.

Answer 1

False! The plasma membrane is selectively permeable.

Question 2

Random molecular movement of substances through the membrane either through a channel or pore.

Answer 2

Passive transport

Question 3

What is the energy source for diffusion?

Answer 3

Kinetic energy of matter; substances tend to move along the gradient from greater concentration to areas of lesser concentration

Question 4

Define active transport.

Answer 4

Transport across a cell membrane that occurs against its electrochemical or concentration gradient and requires the use of ATP.

Question 5

What is the difference between diffusion and osmosis?

Answer 5

Diffusion is the random motion of particles and their tendency to move from areas of higher concentration to lower; osmosis is the movement of water through a semipermeable membrane in the presence of a concentration difference

Question 6

Define osmolarity.

Answer 6

Total concentration of all solute particles in a solution.

Question 7

Hydrostatic pressure

Answer 7

Pressure exerted by water against its surrounding membrane

Question 8

A hypertonic solution will cause a cell to:

Answer 8

lose water and shrink

Question 9

A hypotonic solution will cause a cell to:

Answer 9

swell

Question 10

How is filtration different from diffusion?

Answer 10

Filtration: water and solutes forced through membrane by hydrostatic pressure, rather than by the kinetic forces of molecular motion and the effects of concentration gradients.

Question 11

What types of substances most easily diffuse through the cell membrane?

Answer 11

Lipid soluble molecules, such as oxygen, nitrogen, carbon dioxide, alcohols

Question 12

T/F: thicker cell membrane=slower rate of diffusion

Answer 12

TRUE!

Question 13

How does temperature effect rate of diffusion?

Answer 13

Higher temp=greater rate of diffusion

Question 14

How does molecular weight effect rate of diffusion?

Answer 14

Greater molecular weight=greater resistance, i.e. slower diffusion

Question 15

T/F: protein pores are selectively permeable to certain substances

Answer 15

FALSE! Well, unless a molecule is too big to pass through. Otherwise, they are open for passage. Protein channels, on the other hand, are selectively permeable and/or gated, regulated by electrical signals or chemical binding.

Question 16

What type of gate is activated by a change in electrical potential across cell membrane?

Answer 16

Voltage gated protein channel

Question 17

Define a ligand gated protein channel

Answer 17

Protein channel opened by the binding of a chemical substance (a ligand) with the protein.

Question 18

Give an example of ligand gating in the propagation of nerve signals.

Answer 18

Acetylcholine: ACh opens gate of this channel, allows positively charged ions (Na+, K+, Ca2+) to enter to elicit further APs or trigger muscle contraction.

Question 19

Sodium-Potassium Pump: List substances transported, direction of transport, and amount of each

Answer 19

3 Na+ ions out of cell; 2 K+ ions into cell

Question 20

Major function(s) of Na+K+ pump

Answer 20

Maintains concentration differences across the cell membrane; establishes a negative electrical voltage inside the cell (electrogenic); basis for nerve function and nerve signal transmission; controlling cell volume (preventing too much water from entering the cell when there is a high presence of solute in the cell)

Question 21

Calcium Pump: type of transport, function

Answer 21

Primary active transport; pumps calcium out of the cell; homeostatic function (maintain low intracellular Ca2+ level)

Question 22

Coupling mechanism in which more than one substance are carried across the cell membrane

Answer 22

co-transport

Question 23

Which secondary active transport method involves 1 ion entering and 1 ion leaving the cell simultaneously?

Answer 23

Counter-transport

Question 24

Name the secondary active transport method by which glucose can enter a cell utilizing the transport of ANOTHER ion.

Answer 24

Co-transport: transport carrier protein has 2 binding sites, one for sodium and one for glucose; concentration of Na+ outside the cell provides a gradient/energy for transport to occur

Question 25

What are 2 examples of substances that co-transport with Na+?

Answer 25

Amino acids and glucose

Question 26

What is a general rule for predicting the behavior or water in the presence of solutes across a semi permeable membrane (osmosis)

Answer 26

“water follows salt”

Question 27

Explain osmotic pressure

Answer 27

The exact amount of pressure required to stop osmosis. “Resistance” to the flow of water through a semi permeable membrane that is sufficient to stop the movement of water.

Question 28

What are 3 types of gradient that can exist across a cell membrane?

Answer 28

Concentration difference of molecules, electrical (charge) difference, and pressure difference across a cell membrane may contribute to an electrochemical gradient.