2.5 diffusion

Question 1

What are all cells surrounded by?

Answer 1

Partially permeable membranes

Question 2

What do partially permeable membranes do?

Answer 2

Control material entry and exit

Question 3

Why do all cells need to import substances?

Answer 3

To survive and export waste materials

Question 4

What are the three processes by which substances move across membranes?

Answer 4

Diffusion
Osmosis
Active transport

Question 5

What can movement across membranes be?

Answer 5

Passive or active

Question 6

What does all movement require?

Answer 6

Energy

Question 7

Where does passive movement utilise its energy from?

Answer 7

The natural movement of particles

Question 8

is diffusion passive or active?

Answer 8

Passive

Question 9

Define diffusion:

Answer 9

The passive movement of molecules down a concentration gradient, from an area of high concentration to an area of low concentration across a membrane until there is no more net movement and equilibrium had been reached

Question 10

Give an example of diffusion in the body:

Answer 10

Respiration occurs at gaseous exchange surfaces, oxygen diffuses from the capillaries to the alveoli

Question 11

What sort of molecules diffuse quickly through the phospholipids?

Answer 11

Small Jon polar molecules such as oxygen and carbon dioxide

Question 12

What is fick’s law?

Answer 12

Rate of diffusion is proportional to = (surface area x difference in concentration) ÷ length if diffusion path

Question 13

The shorter the diffusion pathway…

Answer 13

… The faster diffusion happens

Question 14

What is the length of diffusion path?

Answer 14

Membrane thickness

Question 15

What affect will increasing the surface area across which particles diffuse have?

Answer 15

Increase in rate of diffusion

Question 16

What effect will increasing the size of the concentration gradient have?

Answer 16

Increase the rate of diffusion

Question 17

What effect will increasing the distance over which diffusion takes place have?

Answer 17

Decrease rate of diffusion

Question 18

Why does respiration occur quickly?

Answer 18

Because alveoli and capillarity are one cell thick so oxygen is able to quickly diffuse

Question 19

What factors affect the rate of diffusion?

Answer 19

Temperature
Concentration difference 
Thickness of exchange surface
Surface area 
Nature of plasma membrane 
Size and nature of diffusing molecule

Question 20

What effect does increasing temperature have on the rate of diffusion?

Answer 20

The higher the temperature the faster the rate of diffusion as molecules have more kinetic energy so they move faster

Question 21

The greater the concentration difference between the two areas…

Answer 21

The faster the rate of diffusion

Question 22

The thinner the exchange surface…

Answer 22

The faster the rate of diffusion as the shorter the distance particles have to travel

Question 23

The larger the surface area of the membrane…

Answer 23

The faster the rate of diffusion