3.3.2 Gas Exchange

Question 1

Describe changes to the diaphragm upon inspiration. (2)

Answer 1

• Diaphragm contracts
• And flattens

Question 2

Explain how the diaphragm causes air to move into the lungs. (3)

Answer 2

• Diaphragm contracts and flattens
• Increases the volume of the thorax
• Air moves down a pressure gradient and into the lungs

Question 3

Describe how oxygen in the alveoli enters the blood capillaries. (2)

Answer 3

• Oxygen DIFFUSES through the epithelium of the alveoli
• and through the endothelium of the blood capillaries

Question 4

Miner’s lung is a disease caused by breathing in dust in coal mines. The dust causes the alveolar epithelium to become thicker. People with miner’s lung have lower concentration of oxygen in their blood than healthy people.

Describe the path by which oxygen goes from an aveolus to the blood. (2)

Answer 4

• By diffusion
• Through the epithelium of the alevolus and through the endothelium of blood capillaries

Question 5

Explain why people with miner’s lung have a lower concentration of oxygen in their blood. (1)

Answer 5

Thicker alveolar wall so longer diffusion pathway

Question 6

In healthy lungs, a gradient is maintained between the concentration of oxygen in the alveoli and the concentration of oxygen in the lung capillaries.

Describe how ventilation helps to maintain this difference in concentration. (2)

Answer 6

• Air with a higher oxygen concentration DRAWN INTO lungs upon inspiration
• Air with a lower oxygen concentration REMOVED from lungs upon expiration.

Question 7

Give one other way that helps to maintain the difference in oxygen concentration. (1)

Answer 7

Circulation OF BLOOD

Question 8

The diaphragm helps to bring abou the increase in the total volume of air breathed out. Explain how. (3)

Answer 8

• Diaphragm relaxes
• Diaphragm domes
• Volume of the thorax decreases

Question 9

Curve A could be used to find the total volume of air that this person could breathe out in one complete breath. Describe how. (2)

Answer 9

• Extrapolate/ extend the curve
• Read off where curve flattens

Question 10

Destruction of pahgocytes causes the lungs ti be more suspectible to infections. Explain why. (2)

Answer 10

• Phagocytes engulf and destroy pathogens
• Lung infections are caused by inhaling phagocytes/fibres

Question 11

The reduced elasticity of the lungs causes breathing difficulty. Explain how. (2)

Answer 11

• MORE residual air in the lungs as they don’t deflate as much upon expiration
• Reduces OXYGEN concentration between the lungs and the environment
• Reduces rate of OXYGEN diffusion into the blood

Question 12

Apart from reduced elasticity, explain how changes to the lung tissue reduce the effiency of gas exchange. (4)

Answer 12

• Alevolar walls thicken
• Longer diffusion pathway for gas exchange
• Scarred tissue
• Decreases surface area for gas exchange

Question 13

Explain an advantage of a counter-current mechanism. (2)

Answer 13

• Diffusion gradient maintained across the gills
• At every point of contact oxygen concentration in water is higher than the oxygen concentration in the blood
• (or) more oxygen diffuses into the blood

Question 14

Gas exchange in fish takes place in gills. Explain how two features of gills allow efficent gas exchange. (2)

Answer 14

• thin EPITHELIUM so short diffusion pathway
• Many gill filaments and lamellae so large surface area for diffusion
• Counter-current mechanism to maintain diffusion gradient

Question 15

Describe the relationship between body mass and oxygen uptake. (1)

Answer 15

• The higher the body mass, the lower the oxygen uptake per gram of body mass
• Negative corelation

Question 16

Explain what causes the oxygen concentration in the trachae to fall when the spiracles are closed. (2)

Answer 16

• Oxygen used in respiration
• Oxygen moves into cells by diffusion
• More oxygen can’t enter through closed spiracles

Question 17

The insect lives in dry conditions. Suggest an advantage of the pattern of spiracle movements shown in the diagram. (2)

Answer 17

• Spiracles not open all the time
• Less water loss