diffusion & facilitated diffusion

Question 1

define diffusion

Answer 1

diffusion is the net movement of molecules (or ions) from a region of higher concentration to a region of lower concentration. the molecules move down the concentration gradient

Question 2

after a period of time, the molecules in diffusion reach…?

Answer 2

an equilibrium

Question 3

what happens when the molecules in diffusion reach an equilibrium?

Answer 3

the molecules are evenly spread out and this is when there is no net movement from either side of the cell membrane

Question 4

what sort of process is diffusion and why?

Answer 4

a passive process since it doesn’t require energy for it to occur

Question 5

why does oxygen diffuse quickly?

Answer 5

its non-polar

Question 6

why does CO2 diffuse quickly?

Answer 6

its polar but very small

Question 7

why does water diffuse quickly?

Answer 7

its polar but very small

Question 8

what factors affect diffusion?

Answer 8

1.the steepness of the conc gradient- bigger difference between 2 sides of membrane, quicker rate
2. thickness of exchange surface- thinner surface means faster rate
3. surface area- greater SA means faster rate. This is because more molecules can pass at any one moment

Question 9

what is diffusion proportional to?

Answer 9

length of diffusion pathway

Question 10

what sort of process is facilitated diffusion?

Answer 10

its passive

Question 11

how is the diffusion of larger molecules and ions sped up?

Answer 11

they diffuse through carrier proteins or channel proteins through facilitated diffusion passively

Question 12

why is it harder for larger molecules such as amino acids and glucose to diffuse?

Answer 12

they diffuse slowly due to their size

Question 13

why is it harder for charged particles such as ions to diffuse?

Answer 13

they’re water soluble and the centre of the bilayer is hydrophobic

Question 14

explain how carrier proteins work in facilitated diffusion

Answer 14

they change shape to pass the molecule through. They move large molecules across. Different proteins facilitate the diffusion of different molecules
1. a large molecule attaches to the protein
2. the protein changes shape
3. this releases the molecule on the opposite side of the membrane

Question 15

explain how channel proteins work in facilitated diffusion

Answer 15

they form pores in the membrane for charged particles to diffuse through. Different channel proteins facilitate the diffusion of different charged particles

Question 16

what factors affect facilitated diffusion?

Answer 16

1. the conc gradient- the higher the gradient the faster the rate up to a certain point (an equilibrium is reached and rate levels off)
2. the number of channel or carrier proteins- once all are in use, FD can’t happen even if you increase conc gradient