5.3 Diffusion

Question 1

Diffusion is?

Answer 1

net passive movement of particles from a region of high concentration to a region of lower concentration until equilibrium

Question 2

Factors affecting rate of diffusion

Answer 2

Temperature: Higher temperature= greater kinetic energy=higher speed= higher rate

Conc. difference: greater concentration gradient= faster rate due to the overall movement from high to low conc being larger

Question 3

What substances can freely move across membranes

Answer 3

non polar molecules (e.g. O2) diffuse through freely down a conc gradient

Polar molecules like water with partial positive and negative charges can diffuse through membranes (but very slowly)

Question 4

What substances cannot freely move across membranes

Answer 4

hydrophobic interior of membrane repels substances with positive or negative charges like ions

Question 5

Rate of molecule/ions diffusion across membranes is affected by?

Answer 5

surface area: larger the area for exchange, the higher the rate of diffusion

thickness of membrane: the thinner the exchange surface, the higher the rate of diffusion

Question 6

Facilitated diffusion

Answer 6

diffusion across a membrane through protein channels
–> selectively permeable as most protein channels are specific to one molecule or ion

Question 7

Factors that affects the rate of facilitated diffusion

Answer 7

temperature, concentration,
membrane surface area and thickness,
number of channel proteins present

Question 8

Factors that affects the rate of facilitated diffusion

Answer 8

temperature, concentration,
membrane surface area and thickness,
number of channel proteins present