gas exchange

Question 1

SA:V ratio

Answer 1

as a cell increases in size, its surface area to volume ratio decreases

Question 2

ficks law

Answer 2

rate of diffusion is proportional to: surface area x difference in concentration/length of diffusion path (membrane thickness)

Question 3

spiracles

Answer 3

entry points for gas exchange in an insect

Question 4

trachea and tracheoles

Answer 4

series of branching tubes in an insect, tracheoles close to respiring tissues

Question 5

oxgen in insects

Answer 5

as the oxygen is used up at the end of the tracheoles which maintains the diffusion gradient

Question 6

carbon dioxide in insects

Answer 6

as it is produced at the tissues, it diffuses out down its diffusion gradient in the opposite direction

Question 7

gas exchange vs water loss in insects

Answer 7

-there is always a trade off between gas exchange and water loss through evaporation
-an insect can control the opening of the trachea by controlling the spiracles
-the end of tracheoles have fluid inside
-this can also prevent desiccation

Question 8

insects during active periods

Answer 8

-when the muscle is respiring more lactic acid is produced
-lowers water potential
-water moves into muscle
-moves gas/water interface closer to muscle
-oxygen diffuses more in air than water (faster)

Question 9

insect breathing

Answer 9

-rhythmically moves it thoracic region up and down the insect can force air movement through the trachea

Question 10

fish gas exchange structure

Answer 10

-have a small SA:V ratio for gas exchange
-impermeable membrane
-bony fish have four pairs of gills supported by an arch
-along each arch there are gill filaments with lamellae for gas exchange

Question 11

counter current exchange

Answer 11

-blood and water flow across the lamellae in opposite direction
-maintains steep diffusion gradient so that the maximum amount of oxygen diffusing into the deoxygenated blood from the water
-the projections are held apart by water flow
-in the absence of water they stick together meaning fish cannot survive for long out of water
-80% of oxygen absorbed

Question 12

ventilation in fish

Answer 12

-required to maintain a continuous undirectional flow
-begins with fish opening their mouths followed by the lowering of the floor buccal cavity
-this enables water to flow in
-then the fish closes its mouth, causing the buccal cavity floor to rise, increasing the pressure
-water forced over the gill filaments by the difference in pressure between the mouth cavity and opercular cavity
-operculum acts as a valve and pump, water in and out

Question 13

inspiration in humans

Answer 13

-the external intercostal muscles contract, ribs and sternum move up and out
-diaphragm muscles contract, diaphragm flattens
-thorax volume increases
-pressure in lungs reduced below atmospheric pressure
-air flows in

Question 14

expiration in humans

Answer 14

-external intercostal muscles relax, viscera return to a relaxed position, ribs and sternum move down and in
-diaphragm muscles relax, becomes more dome shaped
-thorax volume decreases
-pressure in lungs increased above atmospheric pressure
-air flows

Question 15

alveoli and gas exchange

Answer 15

-very think, one cell thick, surrounded by capillaries, reduces diffusion pathway for gases
-constant blood supply by capillaries means that a steep concentration gradient is maintained
-large numbers of alveoli provides a large surface area

Question 16

cartilage

Answer 16

involved in supporting the trachea and bronchi, plays an important role in preventing the lungs from collapsing in the vent of a pressure drop during exhalation

Question 17

ciliated epithelium

Answer 17

present in bronchi, bronchioles and trachea, involved in moving mucus along the throat to prevent lung infection

Question 18

goblet cells

Answer 18

present in trachea, bronchi and bronchioles involved in mucus secretion to trap bacteria and dust to reduce the risk of infection with the help lysozymes

Question 19

smooth muscle

Answer 19

contract, constricts airway, controls airflow

Question 20

elastic fibres

Answer 20

stretch when we exhale and recoil when we inhale, controls airflow

Question 21

ficks law (alveoli)

Answer 21

-surface area- lots of alveoli, folded, good blood supply
-diffusion gradient- deoxygenated vs oxygenated blood, constant ventilation + blood circulation, maintains diffusion gradient
-diffusion distance- short, alveoli 1 cell thick

Question 22

spirometer

Answer 22

device used to measure lung volume, airtight chamber, trace of a graph

Question 23

vital capacity

Answer 23

the maximum volume of air that can be inhaled or exhaled in a single breath

Question 24

tidal volume

Answer 24

volume we breathe in and out at each breath rest, up and down

Question 25

residual volume

Answer 25

the air that remains in the lungs after max forceful respiration

Question 26

peak flow

Answer 26

how fast one breath can move out

Question 27

forced expiratory volume

Answer 27

how much you can breathe out in one

Question 28

VO2 max

Answer 28

how effective mitochondria area, CO2 and O

Question 29

thick waxy cuticles (plants)

Answer 29

increase diffusion distance so less chance of gas diffusion out so water loss reduced by the cuticle distance

Question 30

hairs on leaves (plants)

Answer 30

hairs trap moist air which decreases the water potential gradient between the inside of the leaves and the outside, the lower the water potential gradient slows the rate of diffusion of water out of the stomata

Question 31

curled leaves (plants)

Answer 31

so that the stomata are sheltered from the wind, wind increases the rate of diffusion of water from outside the plant, so curling the leaves helps reduce the effect oof wind and so it slows the rate of water loss

Question 32

sunken stomata

Answer 32

the stomata of xerophytes are also sunk into pits in the epidermis which trap moist air when then decreases the water potential between the inside of the leaves and the outside, the lower water potential slows the rate of diffusion of water out of the stomata

Question 33

less stomata (plants)

Answer 33

this means that less water is lost when the stomata open for diffusion

Question 34

reduced SA:V ratio (plants)

Answer 34

-the smaller a SA:V ratio, the slower the rate of diffusion -by having leaves that are small and roughly circular in cross section rather than leaves that are broad and flat the rate of water loss can be reduced