3.1.1 - Exchange Surfaces

Question 1

Gas exchange in fish

Answer 1

• Have lamella so there is a large SA for gas exchange
• presence of secondary lamella on primary lamella
• Short distance between blood and water (decreased diffusion distance)
• This maintains a concentration gradient, allowing for a faster rate of diffusion

Question 2

Counter current exchange system

Answer 2

• Blood and water flow in opposite direction across the lamella to maintain the concentration gradient

Question 3

Buccal cavity

Answer 3

• The mouth opening increases volume of the buccal cavity = decreasing pressure, allowing water to move in
• The opercular valves shut and the opercular cavity (containing the gills) expands, causing water to move across the gills
• The opercular valve opens, causing the water to escape

Question 4

Why do larger organisms require specialised gas exchange systems and transport systems?

Answer 4

• Smaller SA:V ratio
• Oxygen cannot quickly diffuse (long diffusion distance) to meet metabolic needs
• Higher metabolic activity

Question 5

Features of an efficient exchange surface

Answer 5

Increased surface area eg root hair cells
= Increased rate of diffusion

Thin layer eg alveoli
= Thin diffusion pathway

Good blood supply/ventilation eg gills
= maintain concentration gradient

Question 6

Goblet cells & Cilia

Answer 6

Goblet cell;
- Secrete mucus, trapping dust/bacteria that enters the lungs

Cilia;
- Waft mucus to the top of the trachea/back of the mouth where it is swallowed or coughed up

Question 7

Elastic fibres role in the lungs

Answer 7

• Recoil to their original shape, expel air and prevent the lungs from bursting
• Return lungs to original size

Question 8

The role of smooth muscle in the lungs

Answer 8

• Smooth muscle in the bronchioles constricts the airway by reducing the diameter of the bronchus

Question 9

Role of cartilage in the lungs

Answer 9

• Provides strength and support for the trachea and bronchi
• Prevents collapse; during breathing in due to pressure decrease in the trachea

Question 10

Gas exchange in insects

Answer 10

• Spiracles allow diffusion of O2 in and CO2 out
• These can close to prevent water loss

Spiracles -> Trachea -> Tracheoles -> Muscles

Question 11

Trachea fluid

Answer 11

Moves from tracheoles to muscles during aerobic respiration = allows more oxygen to enter the muscles, preventing anaerobic respiration

Question 12

Inspiration in mammals

Answer 12

Diaphragm: Contracts and flattens
Ribs: Move up and out
- External intercostal muscles: Contract
- Internal intercostal muscles: Relax
Volume (in thorax): Increases
Pressure: Decreases
Pressure gradient: Air moves into lungs

Question 13

Expiration in mammals

Answer 13

Diaphragm: Relaxes and rises
Ribs: Move down and in
- External intercostal muscles: Relax
- Internal intercostal muscles: Contract
Volume (in thorax): Decreases
Pressure: Increases
Pressure gradient: Air moves out of lungs

Question 14

Spirometer

Answer 14

Used to measure lung capacity

Question 15

Vital capacity

Answer 15

Maximum volume of air a person can breathe out

Question 16

Residual volume

Answer 16

Air that cannot leave lungs

Question 17

Tidal volume

Answer 17

Volume of air breathed in and out at rest
- Apprx. 500cm^3 at rest

Question 18

Breathing rate

Answer 18

**Number of breaths per minute **

Total air breathed per minute = tidal volume x breathing rate

Question 19

Oxygen uptake: Spirometer

Answer 19

The volume of oxygen taken up by the lungs

• The air breathed into a spirometer has the CO2 removed via soda lime; the O2 is used for aerobic respiration