Diffusion

Question 1

what is the definition of diffusion?

Answer 1

the net random movement of particles from an area of higher concentration to an area of lower concentration

Question 1

why do particles move randomly?

Answer 1

due to their kinetic energy

Question 2

what does diffusion describe?

Answer 2

the overall direction and speed of movement

Question 3

what is the equilibrium?

Answer 3

when over time the particles will be equally distributed - this doesn’t mean the particles stop moving

Question 4

what are the four factors that affect the rate of diffusion?

Answer 4

• temperature
• concentration gradient
• distance
• SA:V

Question 5

how does temperature affect diffusion?

Answer 5

at higher temperatures, molecules have more kinetic energy and so move faster - therefore diffusion occurs faster

Question 6

how does concentration gradient affect diffusion?

Answer 6

• if there is a very large difference in concentration between two areas, molecules will diffuse from the higher to the lower concentration quickly
• if the concentration gradient (difference) is small, diffusion will happen more slowly

Question 7

how does distance affect diffusion?

Answer 7

diffusion takes longer if the molecules have to travel further - therefore cells are small (smaller volume reduces distance) - remember molecules do not travel in a straight line which slows the process

Question 8

how does SA:V affect diffusion?

Answer 8

• a larger surface area speeds up the rate of diffusion as there are more opportunities for the molecules to move, which is why surfaces such as alveoli in lungs are so large
• SA:V is more significant, as the two counteract (oppose) each other: an efficient exchange surface has a surface area which is very large compared to the distance the moleules must travel
• SA:V is increased when structures are small