Gas Exchange Flashcards
Fish : explain how the gills allow efficient gas exchange
Thin lamellae provide a large surface area
Thin epithelium so short diffusion pathway
Counter current flow maintains the concentration gradient across whole length of gill
Lots of blood capillaries and thin surface of cells to speed up diffusion between water and blood
Fish: explain how the highly folded structures of the gill lamellae increase the efficiency of gas exchange
They increase the surface area over which diffusion can take place
Fish: describe and explain how the counter current system leads to efficient gas exchange across the gills of a fish
Water and blood flow in opposite directions
This maintains a concentration gradient across the whole length of the gill
As much oxygen as possible passes into the blood
Name the process by which carbon dioxide is removed from a single called organism
Diffuses out across their body surface
How do single celled organism absorb oxygen
Diffusion across their body surface
What do single celled organisms have that’s different to multicellular organisms
Large SA to volume ratio
Insects: explain how the tracheal system limits the size of the insect
The tracheal system relies on diffusion to bring oxygen to respiring tissues if insects were large it would take too long for oxygen to reach the tissues rapidly enough to supply the insects needs
Insects : give 2 explanations as to why the rate of water loss during gas exchange is very low in most insects
Insects have spiracles that can close to reduce water loss
Insects have sunken spiracles that trap moist air
Explain ways in which plants limits water loss
Plants have a waxy cuticle which prevents the evaporation of water
Plants have hairs on their surface (lower epidermis) that trap moist air reducing water potential gradient. So less water lost by evaporation
Plants have sunken stomata which again traps moist reducing water potential gradient
The stomata can close which reduces evaporation
Leaves: why is there is less water lost by a plant when the air is humid
Humidity reduces the difference in concentration of water between the plant and air. Reduced concentration gradient= less water loss
What are xerophytes ?
Plants that are adapted to living in areas where water is in short supply
Give two examples of how xerophytes limit water loss
Thick cuticle - Waxy cuticle Rolled up leaves Hairy leaves Stomata in pits or grooves Reduced surface area to volume ratio Deep roots sunken stomata
Xerophytes: explain how having rolled up leaves reduces water loss
Traps a region of still air within the rolled leaf
The trapped region has a high water potential
No water potential gradient between the inside and outside of leaf and therefore no water loss
Xerophytes: explain how having hairy leaves reduces water loss
Traps still moist air next to the leaf surface
This reduces the water potential gradient between the inside and the outside of the leaves
Less water lost by evaporation
Xerophytes : explain how having stomata in pits or grooves reduces water loss
Trap moist air next to the leaf and reduce the water potential gradient
Why water is always lost from the gas exchange of terrestrial organisms ( insects and plants)
Gas exchange surfaces are permeable
Higher concentration of water molecules inside the animal than outside
Water will diffuse out
Leaves: what happens to oxygen in a plant
Some oxygen from photosynthesis is used in respiration
Most diffuses out of the plant
Plants: in the dark when photosynthesis is not occurring what is happening to oxygen and carbon dioxide
Oxygen diffuses into the leaf because constantly being used by cells during respiration
Carbon dioxide diffuses out of leaf because it is constantly being produced
How is gas exchange similar in insects and plants
No living cell is far from the external air and therefore is a source of oxygen and carbon dioxide
Diffusion takes place in the gas phase (air)
Both have small surface area to volume ratio
How are leaves adapted for rapid diffusion
Air spaces have a very large surface area to volume ratio
Many small pores called stomata so no cell is far from stoma so short diffusion pathway
Numerous interconnecting air spaces that occur throughout the mesophyll so that gases can readily come in contact with mesophyll cells
Large surface area of mesophyll cells for rapid diffusion
At times what can plants do with the gases they produce
The gases produced in one process can be used for the other
Photosynthesis + carbon dioxide
What is each stoma surrounded by
A pair of guard cells
What do guard cells do ?
Open and close the stomata (for example when it is dark)
Why is the stomata being able to open and close important ?
The stomata can close when there will be excessive water loss to minimise water loss
Describe cross section of the leaf
From bottom to top Guard cells Stomata Spongy mesophyll Palisade mesophyll Upper epidermis
How does carbon dioxide in the air outside the leaf reach mesophyll cells inside the leaf
Carbon dioxide enters via stomata
Stomata is opened by guard cells
Diffuses through air spaces
Down concentration gradient
What does the increase in surface area conflict with
Conserving water
Why does every cell inside an insect have a short diffusion distance/ pathway
They are (cell) only short distance from the trachea or tracheoles
Insects: name the tiny pores on the body surface of insects
Spiracles
How much of the time are the spiracles opened and closed for
They are mostly closed to prevent water loss
Insects : periodically spiracles must open why?
To allow for gas exchange to happen
Insects : What is the trachea strengthened by ?
Rings to prevent them from collapsing
Explain gas exchange in insects
Air moves into trachea through pores (spiracles)
Oxygen is used up so its conc gradient towards ends of
tracheoles falls.
Creates diffusion gradient
Oxygen travels down conc gradient
Trachea branches into tracheoles that go to individual cells
Thin permeable walls- oxygen directly to respiring cells
Co2 produced by respiring cells
Conc gradient in opposite direction
Co2 moves down conc gradient and released in atomsphere
Why does abdominal pumping increase the efficiency of gas exchange between tracheoles and muscle tissue of insect
increasing the
amount of air/oxygen entering→maintains greater concentration gradient for diffusion
removal of water from the tracheoles increases rate of diffusion of oxygen between tracheoles and muscle tissue
Greater surface area exposed to the air
Gases diffuse faster in air than water (more rapid)
Increases volume of air
How does the end of the tracheoles fill up with water
Muscles cell around tracheoles respire
Anaerobic respiration
Lactate
Lower water potential of the muscle cells
Water from tracheoles move into cells by osmosis
Decrease volume of water in tracheoles
Further air drawn in
Why do insects require a specialised breathing system ?
Insects posses an exoskeleton
This prevents gases from diffusing through
Many insects have a high metabolic rate so demand for oxygen
How does oxygen in the tracheoles reach muscle cells
Air diffuses along the trachea and tracheoles
Oxygen is then dissolved in water at the end o tracheoles
Here it diffuses into the muscle cells
The supply of oxygen to the flying muscles is affected by ?
Lactate
Produced by anaerobic respiration
Lowers water potential
Fluid from the tracheoles moves into the cells by osmosis
Allowing air oxygen in the tracheoles to diffuse directly into the cells
The diffusion pathway has been shortened
Fish: What happens if blood and water flow in parallel
Diffusion of oxygen into the blood is less efficient
Only 50%
Equilibrium is reached as the concentration gradient cannot be maintained along the whole filament
Xerophytes: how can reduced sa to vol ration in leaves be achieved
Leaves reduced to pine needles
Lungs: what structures does the air pass through
Trachea- bronchi - bronchioles - alveoli
Lungs: what prevents trachea from collapsing
Rings of cartridge
Adaptions of the alveoli
Squamous epithelium = thin/one cell thick
- Short diffusion pathway→fast diffusion
- Large surface area to volume ratio - Fast diffusion
- Permeable
- Good blood supply from network of capillaries
- Maintains concentration gradient
- Elastic tissue allows it to recoil after expansion
Why is the alveolus being one cell thick efficient for gas exchange
Creates a shorter diffusion pathway
Lungs : why is the alveoli having a constant blood supply from capillaries a good thing ?
Steep conc gradient is constantly maintained
Lungs : what happens to the intercostal as we breathe in
External intercostal contract
Internal intercostal relax
What happens in inspiration (breathing in )
External intercostal muscles contract whilst the internal muscles relax
Causes the ribs to raise upwards
Diaphragm contracts and flattens
Volume inside thoracic cavity increases
Pressure decreases
Difference between pressure inside the lungs and atmospheric pressure creates gradient
Air to be forced into the lungs
What happens expiration ?
Internal intercostal muscles contract
External intercostal muscles relax
Causes ribs to lower
Diaphragm muscles relax and raises upwards
Decrease volume inside the thoracic cavity
Increases pressure
Air pushed down pressure gradient
What is vital capacity
The maximum volume of air that can be inhaled or exhaled in a single breath
What is tidal volume
The volume of air we breathe in and out at each breath at rest
What is the residual volume
Volume of air always present in the lungs
How does oxygen in the air reach capillaries surrounding alveolus
Trachea, bronchi, bronchioles Down pressure gradient Down diffusion gradient Across alveolar epithelium Across capillary epithelium
Alveoli adaptions
The alveoli are very thin being only around one cell thick. These are surrounded by capillaries which are also only one cell thick. This reduces the diffusion pathway for gases.
- The constant blood supply by capillaries means that a steep concentration gradient is constantly maintained.
- The are a large number of alveoli (~300 million), collectively giving a surface area of ~70m2.
