Cell Membranes- Diffusion

Question 1

What is diffusion?

Answer 1

The net movement of molecules or ions from an area of higher concentration to an area of lower concentration

Question 2

What way will molecules move?

Answer 2

Both ways but net movement will be to area of lower concentration and this continues until evenly distributed

Question 3

What is the concentration gradient?

Answer 3

Path from an area of higher concentration to an area of lower concentration

Question 4

Which way do particles move?

Answer 4

Down the concentration gradient

Question 5

What kind of process is diffusion?

Answer 5

Passive so no energy is required

Question 6

Can particles diffuse across cell membranes?

Answer 6

Yes, as long as they can move freely through the membrane

Question 7

What is simple diffusion?

Answer 7

When molecules diffuse directly through a cell membrane

Question 8

How do larger molecules diffuse through the phospholipid bilayer?

Answer 8

Extremely slowly because they’re so big

Question 9

How do charged molecules diffuse through the phospholipid bilayer?

Answer 9

Slowly because they’re water soluble and the centre of the bilayer is hydrophobic

Question 10

What does facilitated diffusion do?

Answer 10

Speeds up the diffusion of large molecules and charged molecules with carrier or channel proteins in the membrane

Question 11

How is facilitated diffusion similar to simple diffusion?

Answer 11

Molecules move down a concentration gradient and it is a passive process

Question 12

What do carrier proteins do?

Answer 12

Move large molecules across membranes down their concentration gradient

Question 13

What do different carrier proteins do?

Answer 13

Facilitate the diffusion of different molecules

Question 14

How do carrier proteins allow diffusion of large molecules?

Answer 14

1. A large molecule attaches to a carrier protein
2. Protein changes shape
3. Molecules is released on opposite side of membrane

Question 15

What do channel proteins do?

Answer 15

Form pores in the membrane for charged particles to diffuse through

Question 16

What do different channel proteins do?

Answer 16

Facilitate the diffusion of different charged particles

Question 17

What are the three factors that simple diffusion depends on?

Answer 17

Concentration gradient, thickness of exchange surface, surface area

Question 18

How does concentration gradient affect the rate of diffusion?

Answer 18

The higher it is, the faster the rate of diffusion and as diffusion occurs, difference in concentration between both sides decreases until it reaches equilibrium so diffusion slows down over time

Question 19

How does the thickness of the exchange surface affect the rate of diffusion?

Answer 19

The thinner the exchange surface, the faster the rate of diffusion

Question 20

How does surface area affect the rate of diffusion?

Answer 20

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

Question 21

What is the role of microvilli in diffusion?

Answer 21

Gives the cell a larger surface area so increases rate of diffusion

Question 22

What are the two factors that facilitated diffusion depend on?

Answer 22

Concentration gradient and number of channel or carrier proteins

Question 23

How does the concentration gradient affect facilitated diffusion?

Answer 23

Higher the concentration gradient, faster the rate of facilitated diffusion and when equilibrium is reach the rate of facilitated diffusion will level off

Question 24

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

Answer 24

Once all proteins in the membrane are in use, facilitated diffusion can’t happen any faster so the greater the number of channel or carrier proteins in the cell membrane, the faster the rate of facilitated diffusion