Chapter 3: Transport in cells

Question 1

How is diffusion maximised in the circulatory system?

Answer 1

Alveoli have thin walls with a high surface area, and capillaries have walls only one membrane thick

Question 2

What are alveoli?

Answer 2

Tiny sacs in the lungs where gas exchange between blood and the air takes place

Question 3

How are the lungs adapted to their function?

Answer 3

Moist membranes allow for faster diffusion, thin linings, rich blood supply, breathing (ventilation)

Question 4

What factors affect diffusion?

Answer 4

Temperature, gradient, surface area

Question 5

What are some examples of osmosis (diffusion of water)?

Answer 5

Transpiration in plants, where water enters root hair cells due to the concentration imbalance

Question 6

What are some examples of diffusion in other animals?

Answer 6

Insects get oxygen by diffusion (they have no lungs). Oxygen diffuses through the high-surface area walls of their spiracles (tubes that run into their bodies). Insects cannot grow too large because otherwise their surface area/volume ratio would be too low and they wouldn’t get enough oxygen
Fish gills have high surface areas for maximum diffusion

Question 7

What are some examples of active transport? (opposite of diffusion which requires energy from ATP)

Answer 7

Mineral ions exist in lower concentrations in the soil than in the plant and are absorbed into root hair cells through active transport
The lining of the intestine can move sugars from lower concentrations in the gut to higher concentrations in the blood