Gas exchange Flashcards
What is the definition of diffusion?
The net movement of molecules from an area of higher concentration to an area of lower concentration.
What materials must organisms exchange with their environment?
- Respiratory gases (oxygen and carbon dioxide)
- Nutrients (Glucose, amino acids & lipids)
- Excretory products (CO2 & Urea)
- Heat
What is the significance of surface area to volume ratio for organisms?
A large surface area to volume ratio is essential for effective material exchange.
What happens to the surface area to volume ratio as an organism gets larger?
The surface area to volume ratio decreases as an organism gets larger.
What is Fick’s Law?
Rate of diffusion = surface area x concentration gradient / diffusion distance or pathway.
What makes a good exchange surface?
- Large surface area
- Large concentration gradients
- Thin exchange surface (few membranes or thin walls)
How do insects balance gas exchange and water loss?
Insects have a waterproof covering
- Rigid exoskeleton covered with waterproof cuticle
a small surface area to volume ratio
- to minimise area over which water is lost
control spiracle openings
- to minimise water loss, by controlling it
What is the role of spiracles in insects?
Spiracles are tiny pores that open and close to control water loss by evaporation.
How does oxygen enter an insect’s body?
Oxygen enters through spiracles and diffuses through the tracheae into the tracheoles.
What is the countercurrent flow in fish gills?
Countercurrent flow is when water and blood flow in opposite directions, maintaining a concentration gradient.
What adaptations do fish gills have for efficient gas exchange?
- Many filaments/lamellae for a large surface area
- Thin epithelium for a short diffusion pathway
- Countercurrent flow to maintain concentration gradient
How do mesophyll cells in leaves facilitate gas exchange?
Mesophyll cells photosynthesise, reducing CO2 concentration, causing CO2 to diffuse from air spaces into the cells.
What adaptations do xerophytic plants have to reduce water loss?
- Reduced number of stomata
- Stomata in pits
- Hairs to trap water vapour
- Rolled leaves
- Leaves reduced to spines
- Thick waxy cuticles
How does carbon dioxide enter mesophyll cells in a leaf?
- Via stomata
- Opened by guard cells
- Diffuses through air spaces
- Down diffusion gradient
What is the primary function of the gills in fish?
The gills function as the gas exchange organ in fish, absorbing oxygen from water.
What is the significance of lamellae in fish gills?
Lamellae increase the surface area for gas exchange and contain capillaries for efficient oxygen absorption.
Fill in the blank: The _____ of a leaf is adapted to provide a large surface area for gas exchange.
flat shape
True or False: Larger organisms can rely solely on diffusion for gas exchange.
False
Gas exchange in Single Celled Organisms
Oxygen (O2) is required to produce ATP during aerobic respiration.
Carbon dioxide (CO2) is produced as a waste product during this process. This produces concentration gradients of these gases in opposite directions.
Have large enough surface area to volume ratios to meet their gas exchange needs by diffusion across their cell membranes.
SA:Vol in Larger Organisms
Lower
SA:Vol in Smaller Organisms
Higher
What is the issue with having a large, thin and permeable area in insects?
These features are favourable for evaporation, leading to potentially fatal dehydration
Where does CO2 go when insects aerobically respire?
CO2 exits the insect when the spiracles open by aerobically respiring tissues
What are the features of Tracheoles in insects?
- Small tubes with THIN walls so that the diffusion distance is reduced
- Highly branched so that there is a large surface area
What are the Tracheae in Insects?
Network of tubes supported by strengthened rings.
What is the network of tubes supported by strengthened rings in insects?
Tracheae
How do the tracheae help in gas exchange in insects?
Provides tubes full of air so that diffusion is fast.
Oxygen diffusion in Insects
1) Tissues respire using oxygen, which reduces the concentration of oxygen at the tissue.
2) Oxygen moves from an area of higher concentration to lower concentration so moves from the tracheae to the tissue.
3) This lowers the oxygen concentration in the tracheae so oxygen moves into the tracheae from outside the insect via the spiracles.
Carbon dioxide diffusion in insects
1) Aerobic respiration produces CO2, increasing the concentration at the tissue
2) CO2 moves from an area of high concentration at the tissue to the low concentration in the tracheae.
3) CO2 then moves from high concentration in tracheae to low concentration outside the insect via the spiracles
Ventilation (Abdominal pumping) in Insects
Movement of the insects muscles creates a mass movement of air in and out the trachea.
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.
What can happen if an insect is at rest?
When an insect is at rest, water can build up in the tracheoles
What happens to insects when they fly?
When an insect is at rest, water is built up in the tracheoles
During flight, the insects may partly respire anaerobically and produce some lactate
This lowers the water potential of the muscle cells. As the lactate builds up, water passes via osmosis from the tracheoles into the muscle cells.
Why does water passing from the tracheoles to the muscle cells help insects during flight?
This adaptation draws air into the tracheoles closer to the muscle cells and therefore reduces the diffusion distance for oxygen when its most needed
What are features of fish used for gas exchange?
Gills
Gill filaments
Lamellae
What is a feature of gills in fish?
They have a large surface area
How does water move through a fish?
Water moves in through the mouth and through the gills
Most of the O2 is removed when the water passes through the lamellae
Water containing little O2 leaves through the gill opening
What do gills have?
They have gill filaments which have many lamellae which provides a large SA
Explain two ways in which the structure of fish gills is adapted for efficient gas exchange
Many filaments/lamellae so there is a LARGE SA
Lamellae are thin for a short diffusion pathway
Explain how the counter current mechanism in fish gills ensures the maximum amount of oxygen passes into the blood flowing through the gills (3)
- Water and blood flow in opposite directions;
- Blood always passing water with a higher oxygen concentration in water;
- Concentration gradient of OXYGEN maintained across the ** full length of the gill lamellae**
Why does the countercurrent exist?
The position of the lamellae is at 90 degrees
A fish uses its gills to absorb oxygen from water. Explain how the gills of a fish are adapted for efficient gas exchange. (3)
1 Large surface area provided by many lamellae/filaments so that increases the rate of diffusion 2 Thin epithelium of lamellae so that there is short diffusion distance
3 Counter current so that a concentration gradient along gill is maintained
Adaptations of leaf for gaseous exchange
- Flat – gives LARGER surface area to volume ratio
- Many Stomata – pores to allow air to move in and out of leaf, which maintains a CONC GRADIENT
- Air spaces in leaf so short distance between mesophyll cells and air
Diffusion of CO2 for photosynthesis (plants)
Mesophyll cells photosynthesis which reduces the concentration of CO2 in the cells
CO2 diffuses from the air spaces into the cells
This reduces CO2 concentration in the air spaces so CO2 diffuses into the air spaces through the stomata from the air outside the lead
DOWN A CONC GRADIENT
Diffusion of O2 for photosynthesis in plants
- Mesophyll cells produce O2 as a result of photosynthesis.
- O2 diffuses into the air spaces from the cells
- This increases the concentration of O2 in the air spaces, causing O2 to move from the air spaces to outside the leaf via the stomata.
DOWN A CONC GRADIENT
Adaptations in plants to reduce water loss
At night, the guard cells close the stomata to prevent water loss.
Upper & lower surfaces have a waxy cuticle.
Why do the guard cells close the stomata at night?
Less CO2 is required at this time of day due to the lack of available sunlight for photosynthesis.
This also prevents water loss
Adaptations in Xerophytic plants to reduce water loss
Reduced number of stomata SO Less Surface Area for water loss
Stomata in pits SO reduced concentration gradient of water vapour
Thick waxy cuticles SO reduced diffusion distance of water
Hairs to trap water vapour SO Reduced concentration gradient of water
