diffusion and facilitated diffusion

Question 1

describe the process of diffusion

Answer 1

• net movement of particles from an area of high concentration to a lower concentration down a concentration gradient until equilibrium is achieved

Question 2

why is diffusion is a passive process

Answer 2

• particles have kinetic energy
• particles move down a concentration gradient

Question 3

list 4 factors that effect the rate of diffusion

Answer 3

• surface area
• diffusion distance
• concentration gradient
• temperature

Question 4

how does an increase in temperature effect the rate of diffusion

Answer 4

• increasing the temperature increases the kinetic energy of molecules and the speeds up the diffusion of particles
• rate of diffusion increases

Question 5

how does an increase in surface area effect the rate of diffusion

Answer 5

• the number of particles that can diffuse at a time increases
• increases the rate of diffusion

Question 6

effect of low SA:V ratio on the rate of diffusion

Answer 6

• the cell increases
• decreasing SA:V ratio
• slow the rate substances can diffuse through a cell
• distance required becomes too large

Question 7

how does an increase in the steepness of a concentration gradient effect the rate of diffusion

Answer 7

• the bigger the difference in the concentration / steeper the concentration gradient the faster the rate
• if there are more molecules on one side on a membrane than on the other, at any one moment more molecules will randomly move across the membrane from that side from the other
• a greater difference in concentration means a greater difference in the number of molecules passing in the two directions and therefore a faster rate of diffusion

Question 8

what does Fick’s law state

Answer 8

• rate of diffusion is proportional to the surface area
• rate of diffusion is proportional to the concentration gradient
• rate of diffusion is inversely proportional to the diffusion distance

Question 8

how does an increase in the diffusion distance effect the rate of diffusion

Answer 8

the larger the diffusion distance the slower the rate of diffusion

Question 9

compare the process of facilitated diffusion and active transport

Answer 9

• facilitated diffusion involves channel or carrier proteins whereas active transport only involves carrier proteins
• facilitated diffusion does not use ATP - it is a passive process whereas active transport in an active process - uses ATP
• facilitated diffusion takes place down a concentration gradient whereas active transport can occur against a concentration gradient
  both involve the movement of particles using some form of an intrinsic protein

Question 10

Give two similarities in the movement of substances by diffusion and by osmosis

Answer 10

(Movement) down a gradient / from high concentration to low concentration
Ignore along / across gradient Reject movement from gradient to gradient
Passive / not active processes; OR Do not use energy from respiration / from ATP / from metabolism; OR Use energy from the solution