diffusion- across cell membrane

Question 1

diffusion is the passive movement of particles
how do the particles move

Answer 1

from a high to low concentration
- molecules will diffuse both ways, but the net movement will always be to the area of low concentration until particles are evenly distributed in the liquid or gas

Question 2

what does passive mean

Answer 2

the process doesnt require energy

Question 3

what is simple diffusion

Answer 3

when molecules diffuse directly through the cell membrane

Question 4

why would larger molecules diffuse slower through the bilayer

Answer 4

would diffuse extremely slowly as they are too big and so larger molecules have to use facillitated diffusion

Question 5

why do charged molecules diffuse slowly

Answer 5

due to them being water soluble and the centre of the bilayer is hydrophobic

Question 6

does facillitated diffusion use energy

Answer 6

no

Question 7

role of channel proteins in facillitated diffusion

Answer 7

channel proteins form pores into the membrane for charged particles to diffuse through (down their concentration gradient)
- different channel proteins facillitate diffusion of different charged particles

Question 8

do channel proteins change shape

Answer 8

no

Question 9

do carrier proteins change shape

Answer 9

yes

Question 10

role of carrier proteins in facillitated diffusion

Answer 10

• carrier proteins move large molecules across membranes, down their concentration gradient. Different carrier proteins facilitate the diffusion of different molecules
  1- first a large molecule attaches to a carrier protein in the membrane
  2- then the protein changes shape
  3- this releases the molecule on the opposite side of the membrane

Question 11

what do channel proteins carry

Answer 11

charged molecules

Question 12

what do carrier proteins carry

Answer 12

large molecules

Question 13

what does simple diffusion depend on

Answer 13

1- concentration gradient (higher it is, the faster the rate of diffusion)
2- thickness of the exchange surface- the thinner it is the faster the rate of diffusion
3- the surface area- the larger the surface area the fast of the rate of diffusion

Question 14

role of microvilli in diffusion

Answer 14

• microvilli are small projections formed on the cell surface membrane
• microvilli give the cell a larger surface area
• in human cells, microvilli can increase the cell surface by 600 times.
• a larger surface area means that more particles can be exchanged in the same amount of time, increasing the rate of diffusion

Question 15

what does facillitated diffusion depend on

Answer 15

1- the concentration gradient- higher the concentration gradient the faster the rate of diffusion. As equillibrium is reached the rate of diffusion will level off
2- number of channel/carrier proteins- the more that are available, the faster the rate of diffusion