Gas exchange and lungs

Question 1

What is Fick’s Law

Answer 1

rate of diffusion is proportional to (surface area x difference in concentrator) ÷ thickness of gas exchange surface

Question 2

What are the properties of gas exchange

Answer 2

• large surface area
• alveoli is one cell thick resulting in short diffusion pathway
• good blood supply (ensures there is a constant supply of oxygen and removal of CO2)
• the alveoli have a large surface area to volume ratio
• alveoli is covered by an extensive network of capillaries

Question 3

Is the concentration of oxygen higher in the alveoli? What happens to the pressure gradient?

Answer 3

• The concentration of oxygen is higher in the alveoli than in the red blood cells
• The pressure gradient causes oxygen to leave alveoli and enter red blood cells (where O2 binds to haemoglobin)
• oxygen diffuses down its pressure gradient

Question 4

How is the structure of the mammalian lungs adapted for rapid gas exchange?

Answer 4

• maximising surface area (large surface area in volume to ratio)
• minimising the length of the diffusion pathway (alveoli is one cell thick, really close to the blood in the capillaries)
• maintaining a concentration gradient
• mammalian lungs support the high metabolic rate of mammals

Question 5

What are the 3 properties that the rate of diffusion is dependent on?

Answer 5

the rate of diffusion is dependent on 3 properties
- surface area
- concentration gradient
- thickness of the gas exchange surface

Question 6

How is the rate of diffusion dependent on surface area?

Answer 6

• rate of diffusion is directly proportional to the surface area
• as the surface increases, the rate of diffusion increases

Question 7

How is the rate of diffusion dependent on concentration gradient?

Answer 7

• rate of diffusion is directly proportional to the difference in concentration gradient across the gas exchange surface.
• the greater the concentration gradient the faster the diffusion

Question 8

How is the rate of diffusion dependent on the thickness of the gas exchange surface?

Answer 8

• rate of diffusion is inversely proportional to the thickness of the gas exchange surface
• the thicker the surface the slower the diffusion