Exchange Flashcards
What is the relationship between the size and structure of an organism and its SA:vol ratio?
As the size or structure of an organism increases the SA:vol ratio decreases because vol increases at much faster rate than SA
What things need to be transferred between an organism and its environment?
Oxygen,co2,urea,heat,waste and nutrients
How do you calculate SA:vol ratio?
Assume a uniform shape calculate SA and volume then divide the surface are by the volume
What is Ficks law
Rate of diffusion = surface area x concentration difference / distance
What are the 6 features of a specialist gas exchange surface?
- Large SA to vol ratio increases rate of exchange
- Very thin so short diffusion distance
- Selectively permeable only allows certain materials to cross
- Movement of environmental medium to maintain steep diffusion gradient eg in air as fastest
- Moist surface
- Located internally to be protected
What is the relationship between surface area to volume ratio and metabolic rate?
The higher the metabolic rate the greater the SA:vol ratio so it looses more heat so needs a higher metabolic rate for greater delivery of o2 to the tissues and cells. Generally smaller organisms
How do single celled organisms exchange substances?
Have a large SA:vol ratio so oxygen is absorbed by diffusion across cell membrane the gas exchange surface making it easier to perform gas exchange
How do larger organisms have to perform gas exchange?
Have a transport system
How are insects adapted for efficient gas exchange?
Evolved an internal network of tubes called trachea supported by strengthened rings to prevent collapse. The trachea divides into smaller dead end tubes called tracheoles which extend into the body tissue of the insects. This creates a short diffusion pathway from oxygen in the air to the respiring tissues via the tracheoles
How do insects reduce water loss? When they need large sa:vol ratio for gas exchange?
Waterproof covering on body made up if chitin with a waterproof cuticle. Spiracles can open and close when they close it reduces water loss and also the tracheal system is internal.
What three ways do respiratory gases move in and out of the tracheal system?
- Along a diffusion gradient
- Mass transport
- The ends of tracheoles are filled with water
How does an insect move gas out along a diffusion gradient?
- Along a diffusion gradient when cells respire oxygen is used up so concentration at ends of tracheoles is low so O2 diffuses down trachea and tracheoles where there is a high concentration. When co2 is produced by respiration it creates a diffusion gradient in opposite direction high to low in air out of trachea. Diffusion occurs in air so much more rapid
How do insects move gas by mass transport?
- Mass transport- contraction of muscles of insects squeeze trachea allowing mass movement of air in and out sped up by abdominal pumping
How does air move into the insect due to water at end of tracheoles?
- The ends of tracheoles are filled with water when cells respire anaerobically produces lactate lowering water potential so water moves into cells from tracheoles by osmosis decreasing volume of water in tracheoles so they can draw air further into them the final diffusion pathway is a gas as rapid but greater water evaporation
What have fish evolved for efficient gas exchange?
Gills located behind the head which are a specialist gas exchange surface.
What are gills made up of and how does this help?
Made up of gill filaments stacked up in piles at right angles are gill lamellae which increase the surface area
What happens to water when it gets to the gills?
Forced over the gills
What are gills made up of?
Gill filaments in piles with gill lamellae at right angles which increases surface area
Why are gills needed?
In water there is 25x less oxygen than air
How do fish maintain steep concentration gradients?
Ventilation and good supply
What is countercurrent flow?
Blood moves through the capillaries in the lamella in the opposite direction to the flow of water over the gill lamella.
Why is countercurrent flow more efficient for diffusion?
Diffusion gradient existe over the whole length of the lamella so oxygen is constantly diffusing from the air down a diffusion gradient into the blood
What is parallel flow?
Water and blood flow in the same direction
Why is parallel flow less efficient?
Only maintained along half the lamella so water cant diffuse when saturations are the same in the blood and water so reach equilibrium
Where does most gas exchange happen in the plant?
In the leaves
What two processes do plants perform?
Photosynthesis and respiration
What two things make diffusion fast in plants?
No living cells are far from air and it takes place in the gas phase so more rapid
How is the leaf adapted for exchange?
- Very thin so short diffusion pathways
- Large surface area to volume ratio
- Stomata so gas can come into contact with mesophyll cells and they can open and close due to the guard cells
How is the leaf adapted to reduce water loss?
Stomata closes so reduces water loss by transpiration
What are some adaptations of xerophytic plants to reduce water loss?
- Stomata in pits or grooves to trap moist air reducing water potential gradient
- Rolling up leaves protects lower epidermis traps region of air so no water potential gradient
- Hairy leaves trap moist air reducing water potential gradient
- Reduced surface area to volume ratio for example needles, cacti, holly, desert plants
How are the lungs adapted for gas exchange?
- Large surface to volume ratio
- Reduced heat loss as it is internal
- Thin alveoli and capillary walls reduces diffusion pathway
- Concentration gradient due to capillaries always moving blood away
- Moist
- Pigment transports co2 and o2
- Contains squamous epithelium
What is the trachea and how is it prevented from collapsing?
A flexible airway lined with ciliated epithelium and goblet cells supported by rings of cartilage to prevent collapse when we breathe in
What is the bronchi and how is it prevented from collapsing?
Where trachea splits in two lined with cilia supported with cartilage to prevent collapse
What are bronchioles?
Made up of muscle lined with epithelium cells so they can constrict to control the flow of air in and out of the alveoli
What are alveoli and why do they have elastic fibres?
Minute air sacs at the end of the bronchiole lined with epithelium and elastic tissue so that they can stretch and fill with air then spring back
What is the pathway of blood from the alveolus to the blood?
Moves across epithelium cells of alveolus then down a concentration gradient through the endothelial cells in the capillaries which are just 1 cell thick
What two ways makes diffusion between alveolus and blood so rapid?
- Pulmonary capillaries are thin so red blood cells are slowed down to fit through so more time for diffusion
- Distance reduced red blood cells are flattened against the capillary walls
What are the 6 ways alveoli are adapted for efficient gas exchange?
- Red blood cells are slowed through pulmonary capillaires allowing more time for diffusion
- Distance reduced red blood cells are flattened against capillary walls
- Walls of alveoli and capillaries are thin diffusion pathway is short
- Alveoli and pulmonary capillaries have large SA
- Breathing constantly ventilated lungs and heart pumps blood around alveoli maintaining a steep concentration gradient
- Blood flow through the pulmonary capillaries maintains a concentration gradient
What is correlation?
When a change in 1 or 2 variables is reflected by a change in another variable
What is causation?
When it is scientifically proven that one variable directly causes something else
What are the risk factors for lung disease?
Smoking, air pollution, genetic makeup, infections, occupation
How does asthma effect the lungs?
Muscle walls of bronchi contract and walls secrete more mucus so diameter of airway is reduced so flow of air is reduced
What happens in inspiration?
External intercostal muscles contract while internal intercostal muscles relax
Ribcage moves upwards and outwards
Diaphragm contracts and flattens
Thoracic volume increases so pressure decreases
Air moves into lungs from atmosphere down a pressure gradient
Active process
What happens in expiration?
External intercostal muscles relax while internal intercostal muscles contract
Ribs move downwards and inwards
Diaphragm relaxes and becomes dome shaped
Thoracic volume decreases so pressure increases
Air moves out if lungs down a pressure gradient
Passive process
Energy only needed for forced expiration
What is ventilation?
When air is constantly moved in and out of the lungs called inspiration and expiration to maintain a diffusion gradient across the alveolar epithelium
What is the equation for pulmonary ventilation rate?
Tidal volume x breathing rate
What is tidal volume?
Volume of air normally taken in at each breath
What is breathing rate?
Number of breaths taken in a minute
