2.1 Gas Exchange surfaces

Question 1

What are the properties of gas exchange surfaces?

Answer 1

• Large SA:V
• Steep concentration gradient
• Thin surface

Question 2

Why is a large SA:V useful?

Answer 2

As organisms get larger the SA:V ratio decreases
- There is less SA for the absorption of nutrients/gases/removal of waste, compared to volume
- Greater volume results in a longer diffusion distance between cells

Question 3

Why is a thin membrane necessary?

Answer 3

The exchange surface will be short and it is easier for particles to diffuse across at a constant flow

Question 4

Why is it important to maintain concentration gradient?

Answer 4

If there is a greater difference in conc. across the membrane then there will be a greater rate of diffusion and particles will move across constantly

Question 5

Explain Fick’s Law of Diffusion?

Answer 5

This expresses the relationship between factors that affect diffusion

Question 6

What is Fick’s Law of Diffusion?

Answer 6

rate of diffusion is DIRECTLY PROPORTIONAL to (S.A x Conc. difference) / membrane thickness

SA or Conc. difference ^ = rate of diffusion ^
membrane thickness decreases = rate of diffusion decreases

Question 7

How is the trachea adapted to its function?

Answer 7

• Tube to allow air to travel
• Cartilage that prevents blockage and prevent collapse
• Mucus lines trachea to trap dust and pathogens
• Cillia waft trapped particles out of trachea through airways

Question 8

Explain how bronchi and bronchioles is adapted to its function?

Answer 8

• Thin walls
• Narrow
• Smooth muscle and elastic fibres enable airways to change depending on amount of airflow needed

Question 9

Explain the structure and function of alveoli?

Answer 9

• Found at the end of bronchioles
• Alveolar wall consists of squamous epithelium
• This is thin, permeable and allows easy diffusion
• Alveoli surrounded by elastic fibres, they can be stretched during inhalation
• Alveoli are surrounded by capillaries - creates a steep conc. gradient for gas exchange
• Moisture lining alveoli facilitates diffusion

CO2 diffuses out of capillaries into alveoli for exhaling
O2 diffuses from the alveoli and into capillaries to be carried around the body

Question 10

How are the lungs adapted for efficient gaseous exchange?

Answer 10

Oxygen diffuses out of the alveoli into the blood
CO2 diffuses into the alveoli to be breathed out
- Many alveoli - large SA for diffusion
- Alveoli lining is 1 cell thick - short diffusion pathway
- Capillaries provide a good blood supply - maintain conc gradient