Paper 1 - gas exchange Flashcards
(29 cards)
What is mass transport
Maintains the final diffusion gradient that brings substances to and from the cell membranes of individual cells
It also helps to maintain the relatively stable environment that is tissue fluid
Why do larger animals have a specialised system that fcailitaes gas exchange
The larger the organism the smaller the sa to vol ratio
Gas exchange system overcomes the problem of a long diffusion pathway, allowig for faster diffusion
What does it mean If an organisn has a larger sa to vol ratio
Higher metabloc rate - faster rate of diffusion of O2, faster rate of aerobic respiration, more ATP
What is the investigation into diffusion
- using pink phenolphthalein agar cubes
- to investigate factors affecting diffusion you can change certain variables
- sa to vol ratio = having different sizes and shapes of cubes
- tempo = thermostatically controlled water bath
- conc gradient = using range of acid conc
- phenophylin in the agar will slowly turn colourless as the acid diffuses into the jelly and neutralises the sodium hydroxide
What is ficks law
Rate of diffusion is proportional or equal to SA X conc difference / distance ( diffusion pathway )
What is the tracheal system in insects
- spiracles
- trachea
- tracheoles
What is the movement of 02 through the insect
1) O2 enters through open spiracles into the trachea
2) O2 diffuses through the trachea into the tracheoles
3) O2 is delivered directly to the respiring tissues, down a cocn gradient from air to cells ( due to O2 used in respiration )
4) when spiracles close gas exchange stops
Co2 produced by respiring tissues move in the opposite direction and leaves when spiracles open
What are the adaptions of the tracheal system
- spiracles are small hols in the exoskeleton of an insect they allow diffusion
- tracheoles have thin walls so there is a short diffusion distance
- tracheal system is highly branched with many tracheoles so there is a large SA for gas exchange
- trachea are permeable tubes full of air so fast diffusion of 02 directly into insect tissues
- fluid in the end of the tracheoles that moves out into respiring tissues during excerisise so faster diffusion through the air to the gas exchange surface giving a larger sa for gas exchange
- body of some insects can be moved by muscles to move air through the tracheal system maintaing a high diffusion gradient for O2 and c2
What are the adaptations of terrestrial insects
- exoskeleton made of chitin that has a waxy cuticle to reduce water loss
- body shape may give a smaller SA to vol ratio to minimise water loss
- some spiracles close to prevent water loss
- spiracles have hairs so less water is lost
What is the structure of the gas exchange system in fish
- each fish has 4 gills each side of its head, water moves through the mouth and out through the gills
- each gill is made up of many finger like projections called gill lamellae
- each gill filament has many gill lamelae on their surface to give a large SA for gas exchange
- they are also thin so there is a short diffusion pathway
What is the gill lamellae
- positioned at right angles to the filaments
- contain vast capillary network
- they have a thin epithelium ( for short distance between water and blood )
What is the counter current mechanism in fish
- in bony fish, blood flows through the gill lamellae in the opposite direction to which water flows over them
- this ensures max amount of 02 passes into the blood flowing through the gills as water and blood flow in the opposite directions
- blood is always passing water with a higher O2 conc, so the diffusion gradient is maintained along the entire length of the lamelae
- if wtare and blood flowed in the same direction equilibrium would be reached and so less O2 would diffuse into the blood
How does gas exchange occuring dicotyldenous plants
Occurs through the leaves via the stomata then through the spongey mesophyll toi the palisade mesophyll layer
How is the dictolydenous plant adapted
- stomata iin lower epidermis to allow diffusion of 02 in and co2 out of the spongey mesophyll layer
- spongey mesophyll gives a short diffusion distance between the mesophyll cells and the air
What is the diffusion of co2 for photosynthesus
- palisade mesophyll cells photsyntyhesise using co2 this reduces conc of co2 in the mesophyll
- co2 diffuses from air space into the cells
- this reduces the co2 conc of air spaces causing co2 to diffuse in from the air outside the leaf through the stomata
What Is the diffusion of 02 in plants
- mesophyll cells produce O2 as a result of photosynthesis
- O2 diffuses into the air spaces from the cells
- this increases the cocn of O2 in the air spaces causing 02 to diffuse from the air spaces to the outside of the leaf via the stomata
How does the diffusion of O2 and co2 change in dicotyldenous plants
- air spaces saturated with water vapour from the xylem
- water vapour evaporatesand diffuses out of the stomata
- at night guard cells lose the stomata to prevent water vapour loss
- less c02 is required due to a lack of sunlight
What are the factors affecting the rate of gas exchange in pant s
- more stomata, more co2 uprake, more photosynthesis so fatsre growth
- also means more water vapour lost via transpiration which is needed in photosynthesis
- increase temp increase kinetic energy increases evaporation of water increasing transpiration
- increase humidity
- increase air movement, decreasing trasnpiration
What are xerophytic plants
- live in low water environment
What are the adaptiations of xerophytic plants
- fewer stomata
- hairs to trap water vapour
- stomata sunken in pits to trap water vapour and decrease water potential gradient
- waxy cuticle layer to reduce evaporation and is thick so increases diffusion distance
- leaves rolled or folded to trap water vapour
- some leaves reduced to spines to reduce SA to vol
How do you measure mean diameter using an eyepiece graticuke
- measure each stomata using the eyepiece graticule ensuring you take enough measurements to calculate reliable mean
- calibrate the eyepiece graticule using a stage micrometre
What are the features if the alveoli epithelium
- large SA
- O2 diffuses through squamous alveolar epithelium through smooth endothelium of capillary
- one cell thick - short diffusion pathway
- containes flattened cells - squamous epithelium
- permeable cell layer
What is the purpose of the alveoli
- continually bring oxygenated blood from pulmonary artery and removing oxygenated blood through pulmonary vein
- maintains large cocn gradient between gases in the blood and in the alveoli space
How you calculate pulmonary ventilation rate
PVR = breathing rate x tidal volume
