Module 3: Exchange & Breathing

Question 1

Explain why some organisms need specialised exchange surfaces

Answer 1

Large SA:V ratio
High metabolic rate
Cells too deep in the body for diffusion alone to supply them

Question 2

Describe general features of an efficient exchange surface (e.g root hair cells, alveoli, gills)

Answer 2

Large SA
Thin - short diffusion distance
Steep concentration gradient
Good blood supply

Question 3

Describe the function of cartilage

Answer 3

Strong but flexible
Provides support in the trachea and bronchi
Stops trachea and bronchi collapsing when the pressure is low

Question 4

Describe the function of ciliated epithelium

Answer 4

Waft mucus containing microorganisms to the back of the throat
Prevent lung infections

Question 5

Describe the function of goblet cells

Answer 5

Secrete mucus
Mucus traps dust and microorganisms
Stops substances reaching alveoli

Question 6

Describe the function of smooth muscle

Answer 6

Can relax to widen diameter of trachea, bronchi and bronchioles
More air can flow into the alveoli during exercise
Due to less resistance

Question 7

Describe the function of elastic fibres

Answer 7

Recoil to push air out of lungs during exhalation
Present in trachea, bronchi, bronchioles and alveoli

Question 8

Describe mechanism of ventilation in mammals

Answer 8

During inspiration (ORA for exhalation):
External intercostal muscles contract
Ribs move up and out
Diaphragm contracts and flattens
Volume of trachea increases and pressure becomes lower than atmospheric pressure
Air drawn into lungs

Question 9

Define the term tidal volume and state a typical value

Answer 9

Volume of air moved in and out of the lungs with each breath. Approx 0.4-0.5dm3

Question 10

Define the term vital capacity and state a typical value

Answer 10

Maximum volume of air inhaled after maximum possible exhale. Approx 5dm3

Question 11

Describe how a spirometer works

Answer 11

Patient attaches nose clip and sterile mouthpiece
As they inhale air is drawn out of the chamber. The lid moves down and a downwards line is drawn on the trace
As they exhale air is added to the chamber. Lid moves up and upwards line is drawn on trace
Soda lime absorbs C02
Therefore volume in chamber decreases showing steady downwards pattern on trace.

Question 12

Describe the mechanism of ventilation and gas exchange in bony fish

Answer 12

Fish open mouth
Lowers floor of buccal cavity
Volume of buccal cavity increases
Pressure in buccal cavity lower than pressure in water
Water drawn into the buccal cavity
Fish closes mouth
Pressure inside buccal cavity increases
Operculum opens, water moves backwards, over the gills
Oxygen diffuses into the blood

Question 13

Describe the mechanism of ventilation and gas exchange in insects

Answer 13

If active, spiracles open
Air diffuses through spiracles into the trachea
Then into tracheoles
Oxygen diffuses from tracheoles into the cells
CO2 diffuses from the cells into tracheoles
Muscle contraction can increase the volume of thorax if very active

Question 14

Describe how to dissect the gas exchange system in bony fish

Answer 14

Push back operculum
Remove the gills by cutting each gill arch

Question 15

Why do organisms need to exchange substances?

Answer 15

Organism needs to supply every cell with oxygen and glucose for respiration
Organism needs to remove waste products from cell to prevent damage. Urea is toxic