Gas Exchange

Question 1

Features of efficient gas exchange

Answer 1

• Large surface area - increases rate of diffusion
• Thin surface - short diffusion pathway
• A good blood supply to maintain a steep gradient

Question 2

How are fish adapted for gas exchange?

Answer 2

• They have gills with multiple gill filaments which have lamallae
• Blood and water flow in a counter current system. This ensures a steep diffusion gradient so the maximum amount of oxygen is
  diffusing into the deoxygenated blood from the water along the whole length of the gill filament

Question 3

How are insects adapted for gas exchange?

Answer 3

• Air moves into the trachea through the spiracles
• Oxygen travels down the concentration gradient
• Tracheoles have thin, permeable walls
• They use rhythmic abdominal movements to move air in and out

Question 4

How are plants adapted for gas exchange?

Answer 4

• Leaves have many stomata to allow gases to enter and leave
• Stomata also controls water loss, guard cells swell for them to open
• Short diffusion pathway
• The surface of the mesophyll cells have a large surface area

Question 5

How can insects and plants control water loss?

Answer 5

• Insects close their spiracles, they also have a waterproof waxy cuticle and tiny hairs to reduce evaporation
• Plants stomata open during the day for gas exchange, Water enters making them turgid. When the plant gets dehydrated, guard cells lose water which closes the stomata

Question 6

Xerophytic adaptations

Answer 6

• Stomata sunk in pits to trap moist air
• Layer of hairs on epidermis to trap moist air
• Curled leaves which protect the stomata from the wind
• Reduced number of stomata, so fewer places for water to leave
• Waxy, waterproof cuticles to reduce evaporation

Question 7

Mammalian inspiration

Answer 7

• External intercostal and diaphragm muscles contract
• This causes the ribcage to move up and out and the diaphragm to flatten which increases the volume of the thoracic cavity
• The lung pressure decreases
• Air flows from an area of higher pressure to an area of lower pressure
• Requires energy

Question 8

Mammalian expiration

Answer 8

• External intercostal and diaphragm muscles relax
• Ribcage moves down and in and the diaphragm curves
• The volume of the thoracic cavity decreased and the air pressure increases
• Passive process

Question 9

Gas exchange in the alveoli

Answer 9

• Big surface area due to huge number
• It is surrounded by a network of capillaries
• Oxygen diffuses out of alveoli, across alveolar epithelium and capillary endothelium, into the haemoglobin into the blood
• Carbon dioxide moves out into the alveoli and breathed out

Question 10

How are alveoli adapted?

Answer 10

• Thin exchange surface - one epithelium cell thick, so a short diffusion pathway
• A large surface area
• Constant blood supply due to a large network of capillaries, maintaining a steep concentration gradient between O₂ in the alveoli and O₂ in the blood

Question 11

Why is there no cartilage at the back of the trachea?

Answer 11

So that the oesophagus is not constricted

Question 12

What is equipment is used to measure gas exchange in the lungs?

Answer 12

Spirometer

Question 13

What is tidal volume?

Answer 13

Volume of air in a normal breath

Question 14

What is ventilation rate?

Answer 14

The number of breaths a person takes per minute

Question 15

What is forced expiratory volume?

Answer 15

Maximum volume an individual can expire in one second

Question 16

What is vital capacity?

Answer 16

Maximum volume of air that can be breathed in and out of the lungs

Question 17

What is the equation of Pulmonary ventilation rate(PVR)?

Answer 17

PVR = tidal volume x breathing rate

Question 18

What can cause gas exchange problems?

Answer 18

• Decreased surface area
• Increased diffusion pathway
• Decreased concentration gradient

Question 19

How does ventilation help maintain a steep concentration gradient?

Answer 19

By keeping the O₂ levels in the lungs higher than in the blood

Question 20

What is FEV₁

Answer 20

Volume of air forced out of lungs in 1 second

Question 21

How does Pulmonary Tuberculosis affect breathing?

Answer 21

• Cells build walls around the bacteria forming hard lumps called tubercles
• Infected tissue dies damaging the exchange surface
• This leads to a decrease in tidal volume and fibrosis which can further decrease tidal volume
• So less oxygen is taken up in each breath

Question 22

How does fibrosis affect breathing

Answer 22

• Scar tissue forms in the lungs resulting the lung being able to expand normally as scar tissue is thick and less elastic
• FVC and tidal volume decreases
• Rate of gaseous exchange decreases

Question 23

How does asthma affect breathing?

Answer 23

• The airways become irritated and inflamed
• During an attack, the smooth muscle lining the bronchioles contract and produce a large amount of mucus
• The airways become constricted, air flow is reduced
• FEV₁ is reduced

Question 24

How does emphysema affect breathing?

Answer 24

• Foreign particles are trapped in the alveoli
• Causing inflammation which attracts phagocytes that releases an enzyme that breaks down elastin
• Elastin helps the alveoli to return to their normal shape, so without it it can not recoil to expel air
• It reduces the SA so gaseous exchange decreases
• Increased ventilation rate

Question 25

Describe of when a fish moves forward

Answer 25

• Buccal cavity is lowered
• Water flows in, increasing the volume
• Buccal cavity raises increasing the pressure
• Water forced to move over gills out of operculum

Question 26

How does abdominal pumping maintain a steep conc gradient?

Answer 26

• It causes air with high conc of O₂ to move into the tracheal system constantly
• It keeps a steep conc gradient gradient with CO₂ in cells and CO₂ in the tracheoles

Question 27

How are stomata adapted for gas exchange?

Answer 27

• Have large SA:V ratio
• Spongy mesophyll have air filled holes
• Guard cells change shape which controls the size of stomata

Question 28

What measures the rate of transpiration?

Answer 28

Potometer

Question 29

Why is the shoot cut under water?

Answer 29

• To stop air bubbles from causing an air lock so water cannot move through the leaf

Question 30

Why is the shoot cut at an angle?

Answer 30

• To increase surface area