12.10 Gas Exchange

Question 1

for survival an organism must to what effectively with its environment

Answer 1

exchange materials

Question 2

examples of materials that need to be exchanged -> respiratory gases

Answer 2

O2 and CO2

Question 3

examples of materials that need to be exchanged -> nutrients

Answer 3

glucose, amino acids and lipids

Question 4

examples of materials that need to be exchanged -> excretory products

Answer 4

CO2 and Urea

Question 5

examples of materials that need to be exchanged -> other

Answer 5

heat

Question 6

exchange takes place at the what of the organism

Answer 6

surface

Question 7

the materials absorbed are what by the cell

Answer 7

used (assimilated)

Question 8

the cell / cells of the organism make up its…

Answer 8

volume

Question 9

for exchange to be effective…

Answer 9

the SA of the organism must be large compared to its volume

Question 10

the SA to V ratio gets smaller as what

Answer 10

the object gets larger

Question 11

SA to V ratio decreases as an organism gets…

Answer 11

larger

Question 12

O2 is required to produce what during what

Answer 12

ATP
aerobic respiration

Question 13

when is CO2 produced and as what

Answer 13

produced as a waste product during this process (aerobic respiration)

Question 14

what does this produce (when CO2 is produced in aerobic respiration as a waste product)

Answer 14

produces concentration gradients of these gases in opposite directions

Question 15

all organisms rely on what for the exchange of O2 and CO2 down their concentration gradients

Answer 15

diffusion

Question 16

single celled organisms (protists and prokaryotes) and some small multicellular organisms have what to meet their gas exchange needs by what across their cell membranes

Answer 16

have large enough SA to V ratio
by diffusion

Question 17

larger organisms (humans, other mammals, insects and fish) have what (by comparison) so cannot rely on what (alone) to meet the oxygen demands to what

Answer 17

have relatively small SA to V ratios
can’t rely on diffusion (alone)
demands to all of their cells

Question 18

therefore larger organisms have developed what and systems which have what to ensure the what

Answer 18

developed specialised gas exchange surfaces
have adaptations
ensure the rapid diffusion of gases

Question 19

larger organisms have…

Answer 19

a smaller SA to V ratio

Question 20

smaller organisms have…

Answer 20

a larger SA to V ratio

Question 21

fick’s law (equation)

Answer 21

rate of diffusion = (SA x conc gradient) / diffusion distance or pathway

Question 22

what makes a good exchange surface

Answer 22

• large SA
• large conc gradients
• thin exchange surface (few membrane or thin walls)

Question 23

dilema of terresterial (land living) insects

Answer 23

the need for gas exchange vs the need to conserve water

Question 24

gas exchange insects: the most effective surface for gas exchange is a…

Answer 24

a large, thin and permeable area

Question 25

gas exchange in insects: these features are also favourable for what leading to potentially what

Answer 25

favourable for evaporation potentially fatal dehydration (dessication)

Question 26

insects must therefore do what to water loss and gas exchange

Answer 26

balance them

Question 27

to limit water loss insects may have (2)...

Answer 27

1 waterproof covering over their body surfaces. this is usually a rigid outer skeleton (exoskeleton) covered with a waterproof cuticle 2 relatively small SA to V ratio to minimise the area over which water is lost

Question 28

movement of O2 through the insect

Answer 28

1 oxygen enters the insect through spiracles and into the tracheae 2 spiracles close 3 oxygen diffuses through the tracheae into the tracheoles (down a conc gradient) 4 oxygen is delivered directly to the respiring tissues

Question 29

what happens to CO2 during the process (movement of oxygen through the insect)

Answer 29

CO2 produced by (aerobically) respiring tissues moves in the opposite direction and exits the insect when spiracles open

Question 30

what are tracheoles and how are they adapted for efficient gas exchange

Answer 30

- small tubes with thin walls so that the diffusion distance is reduced which extend throughout the body tissues - highly branched so that there is a large SA

Question 31

what are tracheae and how are they adapted for efficient gas exchange

Answer 31

- network of tubes supported by strengthened rings - provides tubes full of air so that diffusion is fast

Question 32

why diffusion happens in the gas exchange systems (tracheal system) of insects -> O2 diffusion

Answer 32

1 tissues respire using oxygen, which reduces the conc of oxygen at the tissue 2 oxygen moves from an area of higher conc to lower conc so moves from the tracheae to the tissue 3 this lowers the oxygen conc in the tracheae so oxygen moves into the tracheae from outside the insect via the spiracles

Question 33

why diffusion happens in the gas exchange systems (tracheal system) of insects -> CO2 diffusion

Answer 33

1 respiration produces CO2 increasing the conc at the tissue 2 CO2 moves from an area of high conc at the tissue to the low conc in the tracheae 3 CO2 then moves from high conc in tracheae to low conc outside the insect via the spiracles

Question 34

ventilation (abdominal pumping) in insects

Answer 34

movement of the insects muscles creates a mass movement of air in and out of the tracheae (like a bellow action) thus increasing the rate of gaseous exchange they also have small air sacs in their trachea muscles around the trachea contract and pumps the air in the sacs deeper into the tracheoles

Question 35

how do insects get additional oxygen during flight

Answer 35

- when an insect is at rest, water can build up in the tracheoles - during flight, the insect may partly respire anaerobically and produce some lactate (lactic acid) - this lowers the water potential of the muscle cells. as lactate builds up, water passes via osmosis from the tracheoles into the muscle cells - this adaptation draws air into the tracheoles closer to the muscle cells and therefore reduces the diffusion distance for oxygen when its most needed - so faster diffusion through the air to the gas exchange surface - so larger SA for gas exchange

Question 36

what is the gas exchange organ in fish

Answer 36

gills

Question 37

the gills have what

Answer 37

a large SA

Question 38

each fish has how many gills each side of its head

Answer 38

4

Question 38

how does water move in and out of the fish

Answer 38

water moves in through the mouth and out through / over the gills

Question 39

the gills have finger-like projections called...

Answer 39

gill filaments

Question 39

what happens to the oxygen when water moves in and out of the fish

Answer 39

water carrying oxygen enters thriugh the fish's mouth, passes through the lamellae on the gill filaments where most of the oxygen is removed finally water containing little oxygen leaves through gill opening

Question 40

each filament has many...

Answer 40

lamellae (at 90°C to increase SA)

Question 41

points about lamellae

Answer 41

- each gill filament has gill lamellae - gill lamellae are positioned at right angles to the filaments - lamellae contain capillaries - thin epithelium (for short distance between water and blood)

Question 42

explain 2 ways in which the structure of fish gills is adapted for efficient gas exchange (2)

Answer 42

1 many filaments / lamellae so theres a large surface area 2 lamellae are thin for a short diffusion pathway

Question 43

countercurrent flow in fish gills

Answer 43

1 water and blood flow in opposite directions 2 blood always passing water with a higher oxygen concentration (in water) 3 oxygen diffusion / conc gradient maintained across the full length of the gill lamellae / filaments

Question 44

ventilation in fish gills

Answer 44

ventilation so maintains a conc gradient

Question 45

what are 2 cell layers in fish gills

Answer 45

1 thin epithelium of the lamellae 2 endothelium well of the capillary

Question 46

a fish uses its gills to absorb oxygen from water. explain how the gills of a fish are adapted for efficient gas exchange (6)

Answer 46

1 large SA provided by many lamellae / filaments so that increases diffusion / makes diffusion efficient 2 thin epithelium of lamellae / distance between water and blood so there is a short diffusion distance 3 water and blood flow in opposite directions / counter current so that a conc gradient (along gill) is maintained / equilibrium not reached 4 as water always next to blood with lower conc of oxygen 5 circulation replaces blood saturated with oxygen 6 ventilation replaces water (as oxygen removed)