Diffusion

Question 1

What is simple diffusion?

Answer 1

Net movement of molecules from an area of higher to lower concentration, directly through a cell membrane

Question 2

How does concentration gradient affect rate of diffusion?

Answer 2

The steeper the concentration gradient, the faster the rate of diffusion. As diffusion takes place, the concentration gradient decreases until it reaches an equilibrium

Question 3

How does thickness of exchange surface affect rate of diffusion?

Answer 3

The thinner the exchange surface, the faster the rate of diffusion (shorter distance particles have to travel)

Question 4

How does surface area affect rate of diffusion?

Answer 4

The larger the surface area, the faster the rate of diffusion

Question 5

What is facilitated diffusion?

Answer 5

Passive movement of molecules across a cell membrane via a specific trans-membrane protein, from an area of higher to lower concentration

Question 6

What do carrier proteins do?

Answer 6

Move large molecules across the membrane, down their concentration gradient by changing shape when a molecule attaches to it, moving the molecule across the membrane, releasing it on the other side

Question 7

What do channel proteins do?

Answer 7

Form pores in the membrane for charged particles to diffuse through. Different channel proteins facilitate the diffusion of different charged particles

Question 8

How does number of channel / carrier proteins affect rate of facilitated diffusion?

Answer 8

The greater the number of channel / carrier proteins in the cell membrane, the faster the rate of facilitated diffusion. Once all the proteins in a membrane are in use, facilitated diffusion can’t happen any faster even if you increase the concentration gradient