A4 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 and out of the tracheoles.

Question 3

What is the advantage to the insect in 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 reduce water loss.

Question 9

Name structures labelled A, B and C

Answer 9

A = trachea

B = bronchiole

C = diaphragm

Question 10

Explain how 3 adaptation shown by the alveolus increases rate of diffusion.

Answer 10

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

Question 11

Describe how a human breathes in.

Answer 11

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 12

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 12

tidal volume x breathing rate

22.5

Question 13

What does tidal volume mean?

Answer 13

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

Question 14

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

Answer 14

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 15

Explain how gills are adapted for efficient gas exchange.

Answer 15

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 16

List the structures that air passes through in a human

Answer 16

Nose/mouth
Trachea
Bronchus
Bronchioles
Alveoli

Question 17

The diagram show a gill arc. Name structure A

Answer 17

Gill filament

Question 18

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

Answer 18

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

Question 19

The picture shows one of the openings on the side of an insects abdomen.

Name the structure and state its function

Answer 19

Spiracle

Allows air to diffuse into the tracheae

Closes to reduce water loss

Question 20

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

Answer 20

Gets smaller
Needs to develop an efficient exchange surface

Question 21

What is Fick’s law?

Answer 21

Diffusion = SA x Concentration gradient/diffusion distance

Question 22

Describe the process of gas exchange in insects

Answer 22

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 23

Describe and explain how a human breathes out

Answer 23

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 24

How is the volume of a cube calculated?

Answer 24

Volume = length x width x height

Question 25

How is the surface area of a cube calculated?

Answer 25

Surface area = 6 (length x width)

Question 26

List the structures through which air travels into an insect.

Answer 26

Atmosphere –> spiracle –> tracheae –> tracheole

Question 27

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

Answer 27

Increases
Large surface area losing heat.
Small volume replacing heat

Question 28

Explain why a mouse has a high metabolic rate.

Answer 28

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

Question 29

What does countercurrent flow mean and why is it an advantage in a fish gill?

Answer 29

Blood and water flow in opposite directions

Maintains a steep concentration gradient across the gill lamellae