4.2

Question 1

Define diffusion. (3)

Answer 1

(1) the net movement of particles…
(2) from an area of high conc to an area of low conc…
(3) which is a passive process

Question 2

What is the explanation of diffusion? (3)

Answer 2

(1) all particles in a liquid/gas are CONSTANTLY in motion due to the KE they possess
(2) their motion is random
(3) particles are constantly bouncing off one another

Question 3

What is THE difference between active and passive process? (2)

Answer 3

(1) passive = involves the natural, inbuilt motion of particles (KE)
(2) active = involves ATP

Question 4

What factors affect the rate of diffusion? (5)

Answer 4

(1) conc gradient
(2) size of the area
(3) thickness of exchange surface
(4) composition of the membrane
(5) size & nature of the diffusing molecule

Question 5

What is Fick’s Law (to equal diffusion) ? (3)

Answer 5

(surface area X difference in conc.) / length of diffusion path

Question 6

What does facilitated diffusion involve? (2)

Answer 6

(1) carrier proteins
(2) channel proteins

Question 7

What do protein channels do in facilitated diffusion? (2)

Answer 7

(1) they SELECTIVELY allow water-soluble ions to pass through
(2) if the specific ion they transport is present, they open. If not, they close.

Question 8

What do carrier proteins do in facilitated diffusion? (2)

Answer 8

(1) when the specific molecule binds to the protein outside the cell…
(2) …the carrier protein CHANGES SHAPE so that the molecule is released into the cell