Gas Exchange Flashcards
Features of efficient gas exchange
- Large surface area - increases rate of diffusion
- Thin surface - short diffusion pathway
- A good blood supply to maintain a steep gradient
How are fish adapted for gas exchange?
- They have gills with multiple gill filaments which have lamallae
- Blood and water flow in a counter current system. This ensures a steep diffusion gradient so the maximum amount of oxygen is
diffusing into the deoxygenated blood from the water along the whole length of the gill filament
How are insects adapted for gas exchange?
- Air moves into the trachea through the spiracles
- Oxygen travels down the concentration gradient
- Tracheoles have thin, permeable walls
- They use rhythmic abdominal movements to move air in and out
How are plants adapted for gas exchange?
- Leaves have many stomata to allow gases to enter and leave
- Stomata also controls water loss, guard cells swell for them to open
- Short diffusion pathway
- The surface of the mesophyll cells have a large surface area
How can insects and plants control water loss?
- Insects close their spiracles, they also have a waterproof waxy cuticle and tiny hairs to reduce evaporation
- Plants stomata open during the day for gas exchange, Water enters making them turgid. When the plant gets dehydrated, guard cells lose water which closes the stomata
Xerophytic adaptations
- Stomata sunk in pits to trap moist air
- Layer of hairs on epidermis to trap moist air
- Curled leaves which protect the stomata from the wind
- Reduced number of stomata, so fewer places for water to leave
- Waxy, waterproof cuticles to reduce evaporation
Mammalian inspiration
- External intercostal and diaphragm muscles contract
- This causes the ribcage to move up and out and the diaphragm to flatten which increases the volume of the thoracic cavity
- The lung pressure decreases
- Air flows from an area of higher pressure to an area of lower pressure
- Requires energy
Mammalian expiration
- External intercostal and diaphragm muscles relax
- Ribcage moves down and in and the diaphragm curves
- The volume of the thoracic cavity decreased and the air pressure increases
- Passive process
Gas exchange in the alveoli
- Big surface area due to huge number
- It is surrounded by a network of capillaries
- Oxygen diffuses out of alveoli, across alveolar epithelium and capillary endothelium, into the haemoglobin into the blood
- Carbon dioxide moves out into the alveoli and breathed out
How are alveoli adapted?
- Thin exchange surface - one epithelium cell thick, so a short diffusion pathway
- A large surface area
- Constant blood supply due to a large network of capillaries, maintaining a steep concentration gradient between O₂ in the alveoli and O₂ in the blood
Why is there no cartilage at the back of the trachea?
So that the oesophagus is not constricted
What is equipment is used to measure gas exchange in the lungs?
Spirometer
What is tidal volume?
Volume of air in a normal breath
What is ventilation rate?
The number of breaths a person takes per minute
What is forced expiratory volume?
Maximum volume an individual can expire in one second
What is vital capacity?
Maximum volume of air that can be breathed in and out of the lungs
What is the equation of Pulmonary ventilation rate(PVR)?
PVR = tidal volume x breathing rate
What can cause gas exchange problems?
- Decreased surface area
- Increased diffusion pathway
- Decreased concentration gradient
How does ventilation help maintain a steep concentration gradient?
By keeping the O₂ levels in the lungs higher than in the blood
What is FEV₁
Volume of air forced out of lungs in 1 second
How does Pulmonary Tuberculosis affect breathing?
- Cells build walls around the bacteria forming hard lumps called tubercles
- Infected tissue dies damaging the exchange surface
- This leads to a decrease in tidal volume and fibrosis which can further decrease tidal volume
- So less oxygen is taken up in each breath
How does fibrosis affect breathing
- Scar tissue forms in the lungs resulting the lung being able to expand normally as scar tissue is thick and less elastic
- FVC and tidal volume decreases
- Rate of gaseous exchange decreases
How does asthma affect breathing?
- The airways become irritated and inflamed
- During an attack, the smooth muscle lining the bronchioles contract and produce a large amount of mucus
- The airways become constricted, air flow is reduced
- FEV₁ is reduced
How does emphysema affect breathing?
- Foreign particles are trapped in the alveoli
- Causing inflammation which attracts phagocytes that releases an enzyme that breaks down elastin
- Elastin helps the alveoli to return to their normal shape, so without it it can not recoil to expel air
- It reduces the SA so gaseous exchange decreases
- Increased ventilation rate
Describe of when a fish moves forward
- Buccal cavity is lowered
- Water flows in, increasing the volume
- Buccal cavity raises increasing the pressure
- Water forced to move over gills out of operculum
How does abdominal pumping maintain a steep conc gradient?
- It causes air with high conc of O₂ to move into the tracheal system constantly
- It keeps a steep conc gradient gradient with CO₂ in cells and CO₂ in the tracheoles
How are stomata adapted for gas exchange?
- Have large SA:V ratio
- Spongy mesophyll have air filled holes
- Guard cells change shape which controls the size of stomata
What measures the rate of transpiration?
Potometer
Why is the shoot cut under water?
- To stop air bubbles from causing an air lock so water cannot move through the leaf
Why is the shoot cut at an angle?
- To increase surface area
