Exchange surfaces

Question 1

Where does exchange occur and give an example of substances exchanged?

Answer 1

Across plasma membranes

e.g O2, glucose, excretory products like urea

Question 2

How does SA to volume ratio affect exchange rate?

Answer 2

High SA:V = mean large surface area relative to their volume so the diffusion of substances is fast

Low SA:V = mean small surface area relative to their volume so the diffusion of substances is slower

Question 3

Why do multicellular organisms require specialised exchange surfaces?

Answer 3

• cells aren’t in direct contact with the external environment
• diffusion distances between cells and their environment is large
• larger organisms have higher metabolic rates

Question 4

How do singled celled organisms exchange substances?

Answer 4

Diffusion directly across the cell membrane

Question 5

What are the key features of a specialised exchange surface?

Answer 5

Large SA = larger area across which substances can be exchanged
Thin walls = minimise the diffusion distance
Good blood supply and ventilation = maintains steep concentration gradients
Selectively permeable membrane = controls what substances are exchanged

Question 6

Describe the trachea structure?

Answer 6

• wide tube supported by c shaped cartilage to keep air passage open during pressure change
• lined by ciliated epithelium cells moving mucus created by goblet cells towards the throat

Question 7

What is the function of the trachea?

Answer 7

carries air to bronchi

Question 8

Describe the structure of the bronchi?

Answer 8

• supported by rings of cartilage
• lined by ciliated epithelium cells and goblet cells
• narrower than trachea and branch of into 2

Question 9

Describe then function of the bronchi?

Answer 9

allow passage of air into the bronchioles

Question 10

Describe the structure of the bronchioles?

Answer 10

• narrower than bronchi
• mostly made up of smooth muscle and elastic fibres (can contract and relax during ventilation)

Question 11

Describe the function of bronchioles?

Answer 11

allow passage of air into alveoli

Question 12

Describe the structure of the alveoli?

Answer 12

• mini air sacs lined with epithelium cells (site of gas exchange)
• 1 cell thick walls covered with a capillary network

Question 13

Describe the function of the alveoli?

Answer 13

facilitate gas exchange

Question 14

Explain the process of inspiration in the lungs?

Answer 14

• external intercostal muscles contract (internal relax)
• the ribs are pulled up and out
• diaphragm contracts and flattens
• volume of the thorax increases and pressure decreases
• air pressure outside the lungs is higher meaning air moves into the lungs

Question 15

Explain the process of expiration in the lungs?

Answer 15

• internal intercostal muscles contract (external relax)
• the ribs move down and in
• diaphragm relaxes and domes
• volume of the thorax decreases (pressure increases)
• air pressure inside the lungs is higher meaning air moves out the lungs

Question 16

Explain how a spirometer works?

Answer 16

Measures lung volume when a person breathes into a air tight chamber leaving a trace on a graph which shows the volume of the breaths

Question 17

Define vital capacity?

Answer 17

Maximum volume of air that can be taken in or expelled from the lungs in one breathe

Question 18

Define tidal volume?

Answer 18

Volume of air we breathe in and out during each breathe

Question 19

Define breathing rate?

Answer 19

Number of breathes taking per minute

Question 20

How can vital capacity, tidal volume and breathing rate be calculated by using a spirometer?

Answer 20

vital capacity = calculated by finding the maximum amplitude

tidal volume = by finding the amplitude at rest

breathing rate = counting the number of peaks in 1 minute

Question 21

Describe the gills in the fish’s gas transport system?

Answer 21

Supported by arches along which are multiple projections of gill filaments (stacked in piles) surrounded by extensive blood vessels covered by an operculum flap

Question 22

Describe the lamelle in the fish’s gas transport system?

Answer 22

• at a right angle to the gill filaments
• increase surface area
• blood and water flow across them in opposite directions (countercurrent)

Question 23

What are the adaptions of the gills for efficient gas exchange?

Answer 23

Lamellae = provide large SA
Lamellae membranes = thin to minimise diffusion distance
Gills = have rich blood supply to maintain steep diffusion gradients
Countercurrent flow = blood and water creates even steeper conc gradients
Overlapping filament tips = increase resistance slowing water flow over gills allowing more time for gas exchange

Question 24

Explain the process of gas exchange in fish?

Answer 24

• buccal cavity volume increases enabling water to flow in (reduced to increase pressure)
• water is pumped over the lamellae by the operculum (O2 diffuses into the blood stream)
• waste CO2 diffuses into the water and flows back out of the gills

Question 25

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

Answer 25

- maintains a steep conc gradient as water is always next to blood of a lower O2 conc - keeps diffusion rate constant enabling oxygen absorbtion

Question 26

Describe the process of countercurrent flow?

Answer 26

1) blood and water flow over lamellae in opposite directions 2) means O2-rich blood meets H2O most O2 rich when it first moves across gills maximising O2 diffusion into blood 3) O2-poor blood returning from body tissues meets O2-reduced water that has most of its O2 removed still allowing diffusion of O2 into blood 4) maintains steep conc gradient across entire gill

Question 27

What happens when a fish opens it's mouth?

Answer 27

1) when a fish opens its mouth volume of the buccal cavity increases 2) decreases pressure pulling H2O into buccal cavity 3) H2O flows over gills 4) H2O flows out through operculum

Question 28

How does ventilation occur via the buccal cavity?

Answer 28

Process at the buccal cavity opens drives unidirectional water flow for ventilation providing freshly oxygenated H2O and removing CO2

Question 29

Why do insects need efficient gas exchange systems?

Answer 29

Deliver O2 to cells = allows aerobic respiration to occur to release energy for cellular processes Remove CO2 from cells = CO2 builds up produced as a waste product of respiration reducing pH denaturing enzymes

Question 30

What have insects gas exchange systems adapted to balance?

Answer 30

- maximise gas exchange efficiency - minimise water loss

Question 31

What is the purpose of an insect exoskeleton?

Answer 31

Covered with a waterproof cuticle to help prevent water loss

Question 32

What are the main structures of an insect gas exchange system?

Answer 32

Tracheae = are air-filled tubes branching through the body Tracheoles = fine branches of tracheae delivering gases to cells Spiracles = external openings of tracheal system on exoskeleton along the abdomen and thorax

Question 33

What are the adaptions of the trachea?

Answer 33

Reinforced chitin spirals = prevent collapsing Multiple tracheae = increases surface area

Question 34

What are the adaptions of the tracheoles?

Answer 34

Directly penetrate tissues = reduces gas diffusion distance Thin walls = reduce gas diffusion distance Highly branched = maximises surface area Not chitin = allows gas exchange to occur Tracheal fluid = allows O2 to dissolve to aid diffusion reducing water loss

Question 35

What are the adaptions of the spiracles?

Answer 35

Open and close = allows them to control gas exchange with atmosphere and minimise water loss

Question 36

What are the stages of gas exchange in insects?

Answer 36

1) air enters tracheal system through open spiracles 2) air moves into larger tracheae diffusing into smaller tracheoles 3) tracheoles branch throughout body transporting air directly to cells 4) O2 dissolves in water in tracheal fluid diffusing down its conc gradient from tracheoles into body cells 5) CO2 diffuses down its conc gradient out of body cells into tracheoles 6) air then carried back to spiracles via tracheae and released from body

Question 37

How is the concentration gradient maintained in insects?

Answer 37

O2 for respiration = keeps O2 conc low in cells CO2 produced in respiration = keeps CO2 conc high in cells Continuous ventilation = fresh air supplied to tracheal system via spiracles

Question 39

How can lactic acid affect rate of gas exchange?

Answer 39

1) lactic acid accumulation reduces Ψ in tracheal fluid at end of tracheoles 2) H2O leaves tracheoles via osmosis 3) higher SA is exposed for gas exchange