Facilitated Diffusion

Question 1

Definition

Answer 1

Moves particles down a concentration gradient from a higher to a lower concentration, using carrier or channel proteins

Question 2

What is moved by facilitated diffusion?

Answer 2

Large molecules e.g. glucose

Charged particles e.g. polar molecules

Question 3

What type of process?

Answer 3

Still a passive process - no energy is required

Question 4

Carrier Proteins

Answer 4

Move large molecules across membranes down their concentration gradient

Question 5

How do carrier proteins work?

Answer 5

1. A large molecule attaches to a carrier protein in the membrane
2. The protein changes shape
3. This releases the molecule on the opposite side of the membrane

Question 6

Channel proteins

Answer 6

Form pores in the membrane for charges particles to diffuse through, down their concentration gradient

Question 7

Factors that affect facilitated diffusion

Answer 7

Concentration gradient

Number of channel or carrier proteins

Question 8

How does concentration gradient affect FD?

Answer 8

Higher the concentration gradient the fast the rate

Question 9

How does the number of channel or Carrier proteins affect the rate of FD

Answer 9

Once all the proteins in a membrane are in use, FD can’t happen any faster even if you increase the concentration gradient and therefore the greater the number of channel/carrier proteins the faster the rate of FD