topic 4.3 - gas exchange Flashcards
1
Q
gas exchange in small organisms
A
for single-celled organisms (eg amoeba) nutrients/oxygen can diffuse directly into cell from external environment and waste products can diffuse directly out
2
Q
why does gas exchange work like that in small organisms
A
- diffusion distance from outside to inside is very small
- SA:V ration is very large; there is large SA so more substances can diffuse in/out
- metabolic demands are low so they don’t regulate own temp/ don’t use much o2 and produce much co2 hence don’t need gas exchange to happen rapidly
- don’t need specialised gas exchange/ transport systems as diffusion is enough to supply their needs
3
Q
gas exchange in larger organisms
A
larger organisms made up of billions of cells so substances need to travel a long distance from outside to reach cytoplasm of cells
4
Q
what is the metabolic rate like in larger organisms
A
- metabolic rate is higher as they control own body temp and are more active
- more demand for O2 + food and CO2 & waste produced is much higher than in smaller organisms
5
Q
where does gas exchange take place in:
- humans
- fish
- insects
- plants
A
- evolved specialised systems to exchange gases they need in and need to remove
- humans - in lungs
- fish - in gills
- insects - in tracheal system
- plants - in leaves
6
Q
what features make a good gas exchange system
A
- a large SA : V
- thin layers as minimise diffusion distance
- rich blood supply to maintain a steep concentration gradient
- moist surfaces to allow gases to dissolve in it
- permeable surfaces to allow free passage of respiratory gases
7
Q
nasal cavity in humans
A
- main entrance for gases into the body
- the lining secretes mucus and is covered in hairs; external air is ‘filtered’ from dust /small particles and pathogens such as bacteria breathed in
- rich blood supply raises temp of air if needed
- moist surfaces increase level of water vapour in air
- basically, air entering lungs has little effect on internal environment.
8
Q
functions of parts involved in gas exchange in mammals
- nasal cavity
- mouth
- epiglottis
- trachea
A
- Nasal cavity - main route by which air enters gas exchange system
- Mouth - air can enter but it misses out on the cleaning of the nasal system
- Epiglottis - Flap of tissue that closes over glottis when food is swallowed to stop food from entering gas exchange system
- Trachea - Airway to bronchi lined with mucus secreting cells and cilia to move mucus / dust / microorganisms away from lungs.
9
Q
- incomplete rings of cartilage
- left and right bronchus
- lung
- bronchioles
- alveoli
A
- incomplete rings of cartilage - prevent trachea + bronchi from collapsing + allow food to be swallowed and move to oesophagus
- Left & Right bronchus - Tubes leading to lungs (similar to trachea structure but narrower and divide to form bronchioles)
- Lung - organ where gas exchange takes place
- Bronchioles - small tubes that spread through lungs and end up in alveoli. (no cartilage and collapse easily)
- Alveoli - Main site of gas exchange in lungs (tiny air sacs)
10
Q
- Ribs
- Intercoastal muscles
- pleural membranes
- pleural cavity
- Diaphragm
A
- Ribs - protective bony cage around the gas exchange system
- Intercoastal muscles - found between ribs and important in breathing
- Pleural membranes - surround the lungs and + line the chest cavity
- Pleural cavity - space between the pleural membranes usually filled with lubricating fluid that allows membrane to slide easily with breathing movements
- Diaphragm - broad sheet of tissue that forms the floor of chest cavity + important in breathing movements
11
Q
alveoli structure
A
- made of single layer of flattened epithelial cells
- capillaries run close also one cell thick wall
- layer of elastic connective tissue between alveoli + capillaries
- hold everything together and help force air out lungs which are stretched when u breath in (elastic recoil of lungs)
- lung surfactant (phospholipids) coats alveoli - preventing alveoli from collapsing which makes breathing easier
12
Q
gas exchange in alveoli
A
- alveoili has high conc of O2 + blood has high conc of CO2
- o2 diffuses into deoxygenated blood’s red blood cells and makes it oxygenated where its then carried to rest of body to use
- CO2 diffuses into alveoli and is then breathed out
13
Q
adaptations of gas exchange system in mammals
A
- Large SA:V - Many (480-500) alveoli in lungs
- walls of alveoli + capillaries are one cell thick so short diffusion pathway
- Continuous flow of blood in capillaries that maintains conc gradient
- Moist walls for gases to dissolve in
14
Q
what is breathing/ventilation
A
The process in which physical movements of the chest change the pressure so that air is moved in or out
15
Q
process of inhalation
A
- inhalation - taking air into the chest
[active, energy-using process] - muscles around diaphragm contract; lowered & flattened
- intercostal muscles between ribs contracts; raising rib cage upwards & outwards
- volume pf chest cavity increases
- reduces pressure in cavity
- pressure within chest is less than atmospheric pressure in air outside
- air moves in through trachea - bronchi - bronchioles - lungs to equalise the pressure inside and out
16
Q
process of exhalation
A
- taking air out lungs - breathing air out
[passive process] - muscles surrounding diaphragm relax
- moves up into resting domed shape
- intercostal muscles relax; ribs move down & in
- volume of chest cavity decreases
- increase in pressure
- pressure inside . pressure outside
- air moves out of lungs through bronchioles - bronchi - trachea - out
17
Q
gas exchange in insects
A
- have high o2 requirement - their respiratory system evolved to deliver o2 directly to the cells and remove co2 same way
17
Q
How your lungs are protected from pathogens and other harmful particles we may breath in?
A
- we breath in lots of tiny particles /dust /pollen / smoke particles/ pathogens (cause disease)
- respiratory system produces loads of mucus that lines airways & traps these little particles / organisms
- moved up the airway by cilia that sweeps up the back of throat
- mucus swallowed
- acid in stomach & digestive enzymes digest the mucus and what its carrying.
18
Q
spiracles
A
- found along the abdomen of most insect
- they are site of entry/exit of respiratory gases
- opened/closed by sphincters (these also control water loss)
19
Q
trachea
A
- largest tubes
- carry air directly into body for gas exchange with cells
- supported by spirals of chitin - hold the trachea open if they are squished
- Chitin makes trachea impermeable to gases hence little gas exchange takes place in these vessels
- Trachea divides to form narrower tubes - tracheoles
20
Q
tracheoles
A
- narrow tube - a single elongated cell
- no chitin hence are freely permeable to gases
- spread through the tissues of insect
- so small and run between and even penetrate into cells
- most gas exchange occurs in tracheoles
21
Q
adaptation in respiratory process
A
- air enters through spiracles
- air moves along the tracheae and tracheoles via diffusion so it reaches all the tissues
- tracheoles may contain water towards end of their length - limiting penetration of gases
- when insect is very active and needs more O2, lactic acid builds up in muscle tissues - effects osmotic conc
- water moves out of tracheoles to the cells via osmosis - more SA on tracheoles for gas exchange
- all oxygen needed is supplied by gas exchange system - up to 25% of co2 produced is lost through cuticles
22
Q
Some insects have very active lifestyles + very high energy demands.
How do they get extra O2 supplied?
A
- mechanical ventilation
- collapsible tracheae
23
Q
mechanical ventilation
A
- air actively pumped into tracheal system.
- when spiracles open, insects make muscular pumping movements of thorax/abdomen
- changes volume + pressure inside body
- drawing air in and out of trachea & tracheoles
24
collapsible tracheae
- increase volume of air moved through respiratory system
- the ventilating movements of abdomen/thorax inflate/deflate them or some by general body movement
25
why can gas exchange not occur in lungs in fish
- water is a lot dense and thick than air
- air is 20% o2 whilst water has a lot less dissolved o2
- lungs - would use up enormous amount energy to move water in and out
- so gills used instead - water flows over them in 1 direction only
- more effective + efficient in terms of energy for fast moving active animals living in water
26
why does gas exchange occur in the gills in fish?
- have high o2 demand due to high active but cannot gas exchange through their scaly external as its not vry permeable to gases = use gills instead
27
gas exchange in fish
- gills contained in a gill cavity + covered by a protective bony flap called the **operculum**
- operculum is important in maintaining flow of water over the gills, even when fish is stationary
28
structure of the gills
- gill filaments (**lamellae**) occur in large stacks
- gill filaments - main site of gas exchange
- need water to keep them apart = to keep large SA needed
- out of water, gill filaments stick together due to lack of water; exposed SA not enough for effective gas exchange & not enough water & o2 can enter
- have a rich blood supply
- blood leaving gills flows in opposite direction to incoming water
- **(counter current exchange system)**
- steep conc gradient maintained
29
Process of Ventilating the gills in bony fish that have an o…….?
- sharks & rays do not have an operculum
- they have to swim all the time to keep water flowing in through their mouths + out over their gills.
- bony fish have operculum so can ventilate their gills even when not moving
30
process of ventilating in the gills
- The floor of the mouth opens, and the operculum (gill flap) closes.
- The floor of the mouth is then raised to increase the pressure but a valve stops water from leaving.
- The increased pressure forces the operculum open which forces water over the gills
31
adaptation to the gas exchange system in fish
- **Large SA** due to gills ligaments being kept apart by water
- Rich **blood supply**
- **thin walls** (short diffusion distance)
- **Countercurrent exchange system** - blood in gill filaments flow in different direction than the water moving over the gills
- steep **conc gradient** maintained
- **Overlapping gill filaments** - tips of adjacent gill filaments overlap - increased resistance to flow of water - slows down the flow of water over gills surface - gives more time for exchange of gases to occur.
