3.3.2 Gas Exchange

Question 1

(Gas Exchange) Define the term ‘correlation coefficient’.

Answer 1

Scatter diagrams/scattergrams can be plotted and used to identify a relationship between two variables.

Question 2

(Gas Exchange) Fill in the gaps: Just because there is a correlation, ____ ___ mean that there is a ______ ____.

Answer 2

does not
causal link

Question 3

(Gas Exchange) What does a strong correlation consist of?

Answer 3

• Large sample of data points
• Few outliers
• Most plots on/close to line of best fit

Question 4

(Gas Exchange) What are the features of a specialised gas exchange system? (5)

Answer 4

• Large surface area relative to the volume (large SA:VOL ratio).
• Thin so the diffusion pathway is short and gas diffusion is rapid.
• Selectively permeable so specific gases (carbon dioxide and oxygen) can diffuse easily.
• Moist so gases can dissolve easily.
• Maintain a steep concentration gradient using a method of ventilation.

Question 5

(Gas Exchange) What are the examples of specialised gas exchange systems? (3)

Answer 5

Fish (gills)
Insects (tracheal network)
Humans (lungs)

Question 6

(Gas Exchange) Describe the structure of fish gills and how they are adapted for gaseous exchange. (7)

Answer 6

1. Gill arches
2. Pairs of gill filaments
3. Many parallel lamella - large SA:VOL ratio
4. Lamella very thin - short diffusion distance
5. Blood capillaries flow counter current to water
6. Counter current flow maintains concentration gradient along the entire length of the lamella.
7. Blood leaving the gills is almost fully saturated with oxygen / very low carbon dioxide.

Question 7

(Gas Exchange) Describe how fish ventilate their gills to maintain a steep concentration gradient: Inspiration (5)

Answer 7

• The mouth opens
• The operculum closes the opening at the back of the pharynx.
• The floor of the buccal cavity is lowered.
• The volume inside the mouth cavity increases and so the pressure inside the cavity decreases.
• This allows water to flow into the mouth.

Question 8

(Gas Exchange) Describe how fish ventilate their gills to maintain a steep concentration gradient: Expiration (4)

Answer 8

• The mouth closes.
• The floor of the buccal cavity is raised.
• The volume inside the mouth cavity decreases and so the pressure inside the cavity rises, forcing water back over the gills.
• The operculum opens and water flows out.

Question 9

(Gas Exchange) Describe the gas exchange system in insects.

Answer 9

Insect’s abdomen move up and down to change pressure and ventilate the tracheal networks and maintains the concentration gradient.

Tracheoles are ‘open ended’ and filled with fluid to help gases dissolve, speeding up gas exchange with the tissues.

Question 10

(Gas Exchange) What are spiracles, in regards to the gas exchange system in insects.

Answer 10

Valved openings which helps limit water loss by evaporation.

Question 11

(Gas Exchange) What is the purpose of larger trachea and smaller tracheoles?

Answer 11

To provide a large surface area.

Question 12

(Gas Exchange) What are trachea supported by, and why?

Answer 12

Rings of chitin to prevent collapse.

Question 13

(Gas Exchange) Describe how oxygen and carbon dioxide concentrations in trachea change when insects ventilate. (9)

Answer 13

Insect abdomen moves down.
Increase volume and decrease pressure.
Spiracles open and air moves into the tracheae.

Oxygen concentration increases and CO2 concentration decreases as gas exchange through diffusion occurs with the tissues.

Insect’s abdomen moves up.
Decreases volume and increase pressure.
Spiracles close.

Oxygen concentration decreases.
CO2 Concentration increases.

Question 14

(Gas Exchange) Describe the lungs, in regards to the human gas exchange system.

Answer 14

Highly branched network of tubules ending in many air sacs called alveoli - large SA:VOL ratio for ‘gas exchange’.

Question 15

(Gas Exchange) Describe the trachea, in regards to the human gas exchange system.

Answer 15

Flexible airway supported by rings of cartilage to prevent collapse.

Question 16

(Gas Exchange) Describe the bronchi, in regards to the human gas exchange system.

Answer 16

Two tube divisions leading to the left and right lung. Lined with ciliated epithelium and mucus secreting cells to remove dirt particles.

Question 17

(Gas Exchange) Describe the bronchioles, in regards to the human gas exchange system.

Answer 17

Smaller branches with smooth muscle walls. Lined with ciliated epithelium.

Question 18

(Gas Exchange) Describe the alveoli, in regards to the human gas exchange system.

Answer 18

Microscopic, elasticated, very thin air-sacs. Closely associated with pulmonary capillaries. Site of gas exchange.

Question 19

(Gas Exchange) Describe the 6 essential features of the alveolar epithelium as a surface over which gas exchange takes place?

Answer 19

Ventilated from the bronchioles

Thin, flat, one-cell thick alveolar walls

Alveolar epithelium (walls) are folded

Moist

Associated with many capillaries

Capillary cells are thin

Question 20

(Gas Exchange) How does the feature of ‘ventilated from the bronchioles’ aid gas exchange?

Answer 20

Maintains the concentration gradient for gas exchange.

Question 21

(Gas Exchange) How does the feature of ‘thin, flat, one-cell thick alveolar walls’ aid gas exchange?

Answer 21

Short diffusion distance so diffusion is rapid.

Question 22

(Gas Exchange) How does the feature of ‘alveolar epithelium (walls) are folded’ aid gas exchange?

Answer 22

Increases the surface area.

Question 23

Gas Exchange) How does the feature of ‘moist’ aid gas exchange?

Answer 23

Helps gases dissolve (oxygen/carbon dioxide).

Question 24

(Gas Exchange) How does the feature of ‘associated with many capillaries’ aid gas exchange?

Answer 24

Large SA:VOL ratio for gas exchange with the blood.

Question 25

(Gas Exchange) Describe ventilation and the exchange of gases in the lungs: Inspiration. (5)

Answer 25

External intercostal muscle contract.

Diaphragm contracts and flattens out.

Volume in thorax increases.

Air pressure decreases.

Air pressure outside greater than inside so air flows IN, inflating the lungs.

Question 26

(Gas Exchange) Describe ventilation and the exchange of gases in the lungs: Expiration. (6)

Answer 26

Internal intercostal muscle contract
Diaphragm relaxes
Elasticated alveoli recoil
Volume in thorax decreases
Air pressure increases
Air pressure in lungs greater than outside so air flows OUT, deflating the lungs.

Question 27

(Gas Exchange) Write the equation for ‘pulmonary ventilation’.

Answer 27

Pulmonary ventilation rate = tidal volume x breathing rate

Question 28

(Gas Exchange) Describe how the plant xerophytic adaptations to limit water loss of ‘thick cuticle’ and give an example of it.

Answer 28

Stops uncontrolled evaporation from leaf cells.

Example: Cacti and marram grass.

Question 29

(Gas Exchange) Describe how the plant xerophytic adaptations to limit water loss of ‘small leaf SA:VOL ratio’ and give an example of it.

Answer 29

Reduced surface area for evaporation.

Example: Cacti and marram grass.

Question 30

(Gas Exchange) Describe how the plant xerophytic adaptations to limit water loss of ‘stomata sunken it pits’ and give an example of it.

Answer 30

Maintain humid air around stomata so shallower concentration gradient.

Example: Cacti

Question 31

(Gas Exchange) Describe how the plant xerophytic adaptations to limit water loss of ‘leaf hairs’ and give an example of it.

Answer 31

Maintain humid air around stomata so shallower concentration gradient.

Example: Marram grass

Question 32

(Gas Exchange) Describe how the plant xerophytic adaptations to limit water loss of ‘rolled leaves’ and give an example of it.

Answer 32

Maintain humid air around stomata so shallower concentration gradient.

Example: Marram grass

Question 33

(Gas Exchange) Describe how the plant xerophytic adaptations to limit water loss of ‘deep roots’ and give an example of it.

Answer 33

Access deep water sources.

Example: Cacti

Question 34

(Gas Exchange) Describe how the plant xerophytic adaptations to limit water loss of ‘widespread shallow roots’ and give an example of it.

Answer 34

Rapid access to rainwater.

Example: Cacti

Question 35

(Gas Exchange) Describe how dicotyledonous leaves are adapted for gas exchange. (5)

Answer 35

Many small pores
Stomata
Short diffusion distance to cells.
Interconnected air-spaces throughout mesophyll tissue
Large surface area for gas exchange.

Question 36

(Gas Exchange) What 2 functions do lung diseases affect?

Answer 36

Ventilation and gas exchange.

Question 37

(Gas Exchange) State 4 measures of lung function.

Answer 37

• Tidal volume
• Ventilation rate
• Forced expiratory volume (FEV)
• Forced vital capacity (FVC)

Question 38

(Gas Exchange) Describe what ‘tidal volume’ is.

Answer 38

The volume of air in each breath - it’s usually between 0.4 dm3 to 0.5 dm3 for adults.

Question 39

(Gas Exchange) Describe what ‘ventilation rate’ is.

Answer 39

The number of breaths per minute. For a healthy person at rest it’s about 15 breaths.

Question 40

(Gas Exchange) Describe what ‘forced expiratory volume (FEV)’ is.

Answer 40

The maximum volume of air that can be breathed out in 1 second.

Question 41

(Gas Exchange) Describe what ‘forced vital capacity (FVC)’ is.

Answer 41

The maximum volume of air it is possible to breathe forcefully out of the lungs after a really deep breath in.

Question 42

(Gas Exchange) List 4 examples of lung diseases.

Answer 42

Tuberculosis, fibrosis, asthma and emphysema.

Question 43

(Gas Exchange) Explain what tuberculosis, fibrosis, asthma and emphysema reduce and the affects of this.

Answer 43

Reduces the rate of gas exchange in the alveoli.
Less oxygen can diffuse into the bloodstream, the body cells receive less oxygen and the rate of aerobic respiration is reduced. This means that less energy is release and sufferers often feel tired and weak.