transport across membranes

Question 1

what is the definition of diffusion

Answer 1

the net movement of particles from a region of higher concentration to a region of lower concentration

Question 2

factors affecting diffusion

Answer 2

• distance of diffusion: the larger the distance particles have to travel the more collisions take place.
• temperature: particles at higher temperature have more kinetic energy so move at higher speeds
• concentration difference: the greater the difference in concentration between 2 regions the faster the rate of diffusion.

Question 3

what 2 factors affect the diffusion of molecules across a membrane

Answer 3

• surface area: the larger the surface area of an exchange surface the higher the rate of diffusion
• thickness of membrane: the thinner the exchange surface the higher the rate of diffusion.
• polarity: non polar molecules can move down a concentration gradient freely

Question 4

what is facilitated diffusion

Answer 4

• this is the passive movement of molecules down a concentration gradient through channel proteins or carrier proteins.