Exchanging materials

Question 1

exchange of oxygen

Answer 1

• alveoli in lungs

- needed for respiration

Question 2

exchange of CO2

Answer 2

• alveoli in lungs

- waste product of metabolism

Question 3

exchange of water

Answer 3

• nephrons in kidney

- needed for cells to function properly

Question 4

exchange of dissolved food molecules

Answer 4

• small intestine

- needed for respiration

Question 5

exchange of mineral ions

Answer 5

• small intestine

- needed for cells to function properly

Question 6

exchange of urea

Answer 6

• nephrons in kidney

- waste product of metabolism

Question 7

What happens as organisms get bigger?

Answer 7

surface area to volume ratio decreases

they can’t rely on diffusion

need specialised exchange surfaces and transport systems

Question 8

adaptations of capillaries

Answer 8

• wall is one cell thick so diffusion happens quickly
• large surface area:volume so more diffusion can take place
• continual flow of blood maintains a concentration gradient
• substances continue to diffuse out the capillary
• substances are carried to other areas of the body

Question 9

Why do substances need to diffuse out of capillaries quickly?

Answer 9

the blood is continuously moving quickly

Question 10

What would happen if the blood in capillaries stopped flowing?

Answer 10

• concentration of substances would balance
• removing the concentration gradient

-preventing diffusion from occurring

Question 11

diffusion

Answer 11

movement of molecules from an area of higher concentration to an area of lower concentration

Question 12

surface area:volume

Answer 12

given as 1 value:

SA / V

e.g. 0.6, 0.3

Question 13

Why do cells have to be small?

Answer 13

so there is enough surface area to meet the demands of the cells volume

a bigger cell needs more materials, but hasn’t got a large enough SA for all of them to diffuse in

material can only get so far through a cell membrane, so in a cell that is too big the material won’t reach the middle