Gaseous Exchange Flashcards
(35 cards)
What does surface area:volume ratio mean ?
SA of an organism has to be larger than the volume of the organism in order for efficient gaseous exchange
What do small organisms have ?
Large SA:volume ratio
What do small organism have to do to compensate for their large SA:volume ratio ?
With large SA:VOL more heat is lost so organism will have to increase their metabolic activity
How does gaseous exchange occur in single celled organisms ?
- Happens through cell surface membrane due to large SA:VOL
- Short diffusion pathway
- move down a concentration gradient
How does gaseous exchange occur in insects ?
- O2 enter insect via spiracles then into tracheae
- Spiracles close
- O2 diffuses faster through air in tracheae
- O2 diffuses down concentration gradient from tracheae to tracheoles
- Then into respiring tissues
CO2 moves in opposite way
What’re the adaptations of tracheal system ?
- Chitin keep tracheae open in tracheal system
- Tracheoles highly branched so large SA:VOL
- Short diffusion pathway as tracheoles directly supply O2 to respiring tissues CO2 moves
- Tracheoles walls permeable to O2
- Insect abdominal pumps to maintain its conc gradient
How do insects minimise water loss ?
Have exoskeleton covered in waterproof cuticle which is impermeable so reduces water loss
Spiracles close
Small hairs around spiracles trap water and reduce water potential gradient
How does gaseous exchange occur in fish ?
- Water carrying O2 move through mouth and out through gills
- Gills have gill filaments
- Each filament has many lamellae
- Lamellae contain capillaries and is sure of gaseous exchange
- Water carrying O2 passes through lamellae and most of O2 is removed and enters capillaries
- Water with little O2 leaves via gill opening
What’re the adaptations of the gill ?
- Many gill filaments containing many lamellae providing large SA for diffusion
- Lamellae have thin epithelium for short diffusion distance between water and blood
- Lamellae placed at right angles to allow water to pass through gills
What’s countercurrent flow ?
Blood and water flow in opposite directions
Creating concentration gradient
Over the entire length of gills
How does gaseous exchange occur in leaf ?
Occurs in leaf
- CO2 in atmosphere enters leaf via stomata
- Then diffuses into air spaces of spongy mesophyll down conc gradient
- CO2 move from air spaces into palisade mesophyll cells for photosynthesis to occur
O2 moves in opposite directions
What’re the adaptations of the plant for efficient gaseous exchange ?
Leaves are flat so large SA:VOL
Leaves contain many stomata
Air spaces shorter diffusion pathway
What’re the adaptations of plant to reduce water loss ?
At night guard cells close stomata due to less rate of photosynthesis so not require as much CO2
Upper and lower epidermis layer have waxy cuticle
Most stomata found on lower epidermis
Air spaces saturated with water vapour from xylem reducing water potential gradient
What’re the adaptations of xerophytes to reduce water loss ?
Thick waxy cuticle increases diffusion pathway so reduces transpiration
Hairs around stomata and stomata pits and rolled leaves trap water vapours decreasing water potential gradient
Leaves reduce to spine decrease SA:VOL
How does gaseous exchange occur in lungs ?
- O2 goes in nasal and oral cavity
- Then to trachea
- Then bronchi
- Then bronchioles
- Then alveoli
- Then epithelial cell of alveoli
- Then endothelium cell of alveoli
CO2 in opposite direction
What’re the adaptations of the lungs ?
Alveoli has large SA and large blood supply which ensures conc gradient
Epithelium and endothelium cells of alveoli are one cell thick which decades diffusion pathway
CO2 and O2 are non polar so enter via simple diffusion and epithelial cell of alveoli are permeable to these gases
What is ventilation ?
Results of difference in pressure between lungs and air outside body
How does inhalation occur ?
- External intercostals contract pulling ribcage up and out
- Diaphragm contacts and flattens
- Thoracic cavity volume increase and pressure in lungs decreases
- air moves down pressure gradient into lungs from atmosphere
How does exhalation occur ?
- Internal intercostals contract pulling ribcage in and down
- Diaphragm relaxes and returns to dome shape
- thoracic cavity volume decreases and the pressure in lungs increases
- air moves down pressure gradient out of lungs and into atmosphere
What is the equation for pulmonary ventilation ?
Tidal volume x breathing rate
What is pulmonary ventilation ?
Total volume of air moved through lungs per min (dm^3/min^-1)
What’s tidal volume ?
Amount of air inhaled and exhaled in a normal breath (dm^3)
What’s breathing rate ?
Number of breaths per minute (min^-1)
What’re the risk factors for lung disease ?
Smoking
Air pollution
Genetic makeup
Infections
Occupation
