cell structure (diffusion)

Question 1

what is diffusion?

Answer 1

the net movement of particles from an area of high concentration to an area of lower concentration

Question 2

what is simple diffusion?

Answer 2

when molecules diffuse directly through a cell membrane

Question 3

what is facilitated diffusion?

Answer 3

diffusion using carrier or channel proteins

Question 4

why is facilitated diffusion necessary?

Answer 4

large molecules would be too big to pass through the membrane
charged particles would diffuse slowly as they are water soluble, and the centre of the bilayer is hydrophobic

Question 5

what do carrier proteins move across a membrane?

Answer 5

large molecules

Question 6

how do carrier proteins work?

Answer 6

large molecule attaches to a carrier protein in the membrane
protein changes shape
releases the molecule on the opposite side of the membrane

Question 7

what do channel proteins move across a membrane?

Answer 7

charged particles

Question 8

how do channel proteins work?

Answer 8

form pores in the membrane for charged particles to diffuse through

Question 9

what does the rate of simple diffusion depend on?

Answer 9

the concentration gradient (larger=faster diffusion)
thickness of the exchange surface
the surface area

Question 10

what does the rate of faciliated diffusion depend on?

Answer 10

the concentration gradient, number of channel/carrier proteins