Gas Exchange

Question 1

How do single called organisms gain the oxygen they require for respiration?

Answer 1

Diffusion across cell membrane.

Surface area is huge compared to the volume.

Question 2

What are spiracles?

Answer 2

Holes in the abdomen of insects. Used to let air into the tracheoles.

Question 3

What is the advantage to the insect in opening and closing the spiracles?

Answer 3

Conserve water when closed

Question 4

How does the countercurrent exchange system maximise oxygen absorbed by fish?

Answer 4

Blood and water flow in opposite directions across the gas exchange surface in fish.
Water containing the highest concentration of oxygen meets blood already containing some oxygen
Maintains a steep concentration gradient across the whole lamellae.

Question 5

How is surface area:volume ratio calculated.

Answer 5

Surface area / volume

Question 6

Why is countercurrent an advantage for gas exchange?

Answer 6

Water containing the highest concentration of oxygen meets blood already containing some oxygen
Allows diffusion across the whole gas exchange surface

Question 7

What is the function of stomata?

Answer 7

Open to increase the rate of diffusion of air into the leaf.

Question 8

Explain why plants only open stomata during day time.

Answer 8

Maximise the amount of carbon dioxide entering the leaf.

Close at night to prevent water loss.

Question 9

Give 3 adaptation shown by the alveolus to increase rate of diffusion.

Answer 9

Large surface area.
Short diffusion distance created by flattened cell making up the epithelium.
Blood capillary close to gas exchange surface.
Large concentration gradient - maintained by ventilation of lungs.

Question 10

Describe how a human breathes in.

Answer 10

Diaphragm contracts and moves downwards (flattens).
External intercostal muscles contract. 
Internal intercostal muscle relax
Ribs move out and up.
Volume in thorax increases. 
Pressure in thorax decreases. 
Air is sucked into the lungs.

Question 11

What is the equation for pulmonary ventilation rate is:

What is the pulmonary ventilation when the breathing rate is 15 breathes per minute and the tidal volume is 1.5 litres.

Answer 11

tidal volume X breathing rate

22.5

Question 12

What does tidal volume mean?

Answer 12

The volume of air breathed in with each breath when the body is at rest.

Question 13

Explain how gills are adapted for efficient gas exchange.

Answer 13

Lamellae provide a large surface area for diffusion to happen
Thin squamous epithelium so has a short diffusion distance
Counter current flow maintains concentration gradient across whole length of lamellae.

Question 14

List the structures that air passes through in a human

Answer 14

Nose/mouth
Trachea
Bronchus
Bronchioles
Alveoli

Question 15

Describe the trachea and its function in the mammalian gas exchange system

Answer 15

Wide tube supported by C-shaped cartilage to keep air passage open
Lined by ciliated epithelium cells which move mucus towards the throat to be swallowed

Question 16

Explain the adaptations shown by alveoli for efficient gas exchange

Answer 16

Large surface area for diffusion
Squamous epithelium for a short diffusion distance
Rich blood supply - maintains concentration gradient and a short diffusion distance, preventing lung infections
Carries air to the bronchi

Question 17

Describe the pathway of an oxygen molecule from the alveolus to the blood

Answer 17

Diffuses across single squamous cell of the alveolar epithelium
Diffuses across the single squamous cell of the capillary endothelium

Question 18

What happens to the surface area:volume ratio as an organism gets larger?

Answer 18

Gets smaller

Needs to develop an efficient exchange surface

Question 19

What is Fick’s law?

Answer 19

Diffusion = SA X Concentration gradient/diffusion distance

Question 20

Describe the process of gas exchange in insects

Answer 20

Gases move in and out of the tracheae through the spiracles
Diffusion gradient allow oxygen to diffuse into body tissue and carbon dioxide to diffuse out
Contraction of muscles (abdominal pumping) allows mass movement of air in and out

Question 21

Name and describe the two main features of a fish gas exchange system

Answer 21

Gill -

Question 22

Describe and explain how a human breathes out

Answer 22

External intercostal muscle relax
Internal intercostal muscle contract
Ribs move down and in
Diaphragm relaxes and becomes domed
Volume of thorax decreases
Pressure in thorax increases
Air is forced out of the lungs

Question 23

How is the volume of a cube calculated?

Answer 23

Volume = length x width x height

Question 24

How is the surface area of a cube calculated

Answer 24

Surface area = 6 (length x width)

Question 25

List the structures through which air travels into an insect.

Answer 25

Atmosphere –> spiracle –> tracheae –> tracheole

Question 26

In mammals as the surface area to volume ratio increase what happens to the rate of heat loss?

Answer 26

Increases
Large surface area losing heat.
Small volume replacing heat

Question 27

Explain why a mouse has a high metabolic rate.

Answer 27

Large surface area to volume ratio
Loses heat rapidly
Needs high metabolic rate to release heat
To maintain body temperature