gas exchange Flashcards
what’s flicks law?
shows the relationship between the rate of diffusion and the three factors that affect diffusion.
describe and explain three features of gas exchange system to maximise the rate of gas exchange
1) large surface area to increase rate of diffusion (more places for molecules to diffuse across the membrane)
2)very thin diffusion pathway, so pathway is short
3)movement of environmental medium to maintain diffusion gradient eg ventilation in air
4)movement of internal medium to maintain diffusion gradient eg blood flowing
what is the outside of an insect called? and what are the properties of it?
exoskeleton made of chitin/ waterproof/ impermeable
what are the small pores down an insects thorax and abdomen called?
spiracles
explain why the spiracles open and close
spiracles open and close using a valve. they open in response to high CO2 concentration/ low oxygen concentration forced open due to abdominal pumping or muscle contraction so that gas exchange can occur. they close to limit water loss
describe the pathway that oxygen must take from the air to the cells of an insect
1) the spiracles connect to a network of internal tubes called trachea which are filled with air
2)trachea branch into small tubes called tracheoles
3)the end of the tracheoles are filled with tracheal fluid and are in contact with fluid around the insects cells
4)tracheoles are highly branched extend throughout all body tissues of insect so air is brought directly to respiring tissues
what are the features of the insect gas exchange system that allows for rapid exchange of gases?
tracheoles are thin, the tracheal system is highly branched, highly branched so short diffusion distance to cells, can be ventilated by abdominal pumping or muscular contractions to maintain the diffusion gradient for oxygen
what is the name of the polysaccharide that keeps the tracheae open? why is it an advantage to have it
chitin
stops it fro collapsing
why is the size of an insect limited?
by the relatively slow diffusion of oxygen to cells
if an insect sees a predator how can it rapidly increase the rate of exchange?
abdominal pumping , muscle contraction, exercise
abdominal pumping
rhythmic contractions of the abdomen compresses the tracheal system this decreases the volume of the tracheal system and increases pressure. this causes the movement out of the spiracles down a pressure gradient. Expels air containing carbon dioxide and brings fresh air in which maintains the oxygen concentration gradient
muscle contraction
contraction of muscles during exercise compresses the tracheal system. This decreases the volume of the tracheal system an increases the pressure. this causes movement of air out off the spiracles down a pressure gradient. when the muscles relax, compression stops and air fills the tubes, this maintains the oxygen concentration gradient
exercise
lactate is produced which is double and lowers the water potential of the muscle cells, air is brought further down tracheloles decreasing diffusion distance and increasing rate of diffusion.
describe how the structure of the insect gas exchange system provides cells with sufficient oxygen and limits water loss
1)spiracles tracheae and tracheoles
2)spiracles allow diffusion
3) tracheoles are highly branched so large surface area
4)tracheal walls are thin so short diffusion distance
5) trachole walls are permeable to oxygen/air
6) exoskeleton is impermeable so reduces water loss
7)spiracles can close to reduce water loss
why do fish need a specialised gas exchange system?
water contains relatively low concentration of oxygen. it is much denser and more viscous than air
fish have gills which have a humber of adaptations to maximise the amount of oxygen that can be obtained from water
1)large surface area to maximise gas exchange (due to filaments and lamelle)
2)blood flow to maintain a concentration gradient
3) thin layers of cells so short diffusion distance
4)countercurrent mechanism
5)ventilation (maintains concentration gradient)
describe the process of ventilation in a fish
water that is rich in oxygen enters the mouth of the fish (ducal cavity). the mouth closes the floor of the mouth moves inwards decreasing the volume of the bucal cavity increasing the pressure which forces the water over the surface of the gills then out through the operculum.
explain the adaptions of the fish gills for the rapid exchange of oxygen
each gill arch contains many Gil filaments which provide a large surface area for gas exchange. the gill filaments also contain many further folds called lamella have rich blood supply provided by capillaries. the lamellae consist of a thin layer of cells for short diffusion distance for oxygen from water into the blood. counter current mechanism to maintain the concentration gradient along the entire length of gills. movement of external medium using ventilation. movement of internal medium blood flows to replace blood saturated with oxygen with deoxygenated blood from body
what is the countercurrent mechanism?
blood flows in opposite direction to water blood that is already loaded with oxygen meets water which has its maximum concentration of oxygen. therefore, diffusion of oxygen from the water into the blood occurs. water that has most of its oxygen removed meets blood that has little oxygen. therefore diffsion of oxygen into the blood occurs. a concentration gradient is present along the entire length of the gill filament. therefore diffusion of oxygen into the blood occurs along the entire length of the gill filament
what’s parallel flow?
Parnell flow is where the blood and water flow is in the same direction. water with its highest concentration of oxygen meets blood with its lowest concentration of oxygen and gas exchange occurs. eventually along the length of the gill filaments an equilibrium is reached so no further exchange occurs. this would limit the uptake of oxygen into the blood
why Is the counter currently mechanism is more efficient than a parallel flow current
a concentration gradient is present along the entire length of the fish providing a faster rate of diffusion
what metabolic processes occur in the leaf cells?
respiration, photosynthesis
why do plants have a lower oxygen requirement than animals?
lower metabolic rate, lower rate of aerobic respiration needed as less ATP required
adaptions in plants that allow photosynthesis to occur
stomata, large air spaces
stomata
pores that allow gases to pass in and out of the leaf. these are numerous so that no cell is far away from stoma so diffusion pathway is short