Substances Can Cross Membranes by Passive Processes

Question 1

Membranes have __ through __ & __.

Answer 1

selective permeability; passive transport; active transport

Question 2

Where does the energy for passive transport come from?

Answer 2

the concentration gradient

Question 3

List the five factors that determines diffusion rate.

Answer 3

• size & mass of molecules or ions
• temperature of solution
• density
• concentration gradient
• area & distance

Question 4

Diffusion of water

Answer 4

osmosis

Question 5

What are the three types of diffusion of water? Explain.

Answer 5

isotonic - equal water, hypotonic - more water in cell than outside, hypertonic - more water outside cell than inside

Question 6

Facilitated diffusion

Answer 6

polar & charged molecules diffuse with concentration gradients, but facilitated by protein channels or carriers

Question 7

the integral membrane proteins that form a tunnel

Answer 7

channel proteins

Question 8

membrane proteins that bind some substances & speed their diffusion through the bilayer

Answer 8

carrier proteins

Question 9

Ion channels are channel proteins with __ pores. Most are __

Answer 9

hydrophilic; gated

Question 10

__ opens when the protein is __ to change shape by a chemical signal (_) or electrical charge difference (voltage-gated).

Answer 10

gate; stimulated; ligand

Question 11

What does the rate of diffusion depend on?

Answer 11

concentration gradient & # of carrier proteins

Question 12

The diffusion system is saturated if all __ are loaded.

Answer 12

carriers