Organisms Exchange Substances Flashcards
How do you calculate the volume of a cell?
4πr3/3
How do you calculate the area of a cell?
4πr²
What are the steps in gas exchange in insects?
1) O2 molecules enter via the spiracle then proceed town the branching tracheae to the tracheoles
2) terminal tips of tracheoles are sometimes fluid-filled, so gas transport may occur in a liquid medium
3) O2 then moves across the tracheolar walls, though the haemolymph, across the plasma membranes of cells and finally through the cytoplasm to the mitochondria
4) CO2 generally follows a reverse path
What are spiracles?
Tiny pore-like holes in the epidermis
Entrance and exit for respiratory gases
Can be opened and closed by sphincters - reduce water loss
When insect is active, O2 demand increases and more spiracles open
What are tracheaes?
1mm - diameter
Carry air directly from spiracles to the body for gas exchange
Held open by spirals of chitin - hold tracheae open if compressed during flight
Chitin makes up scaffolding supporting the epidermis - practically impermeable to gases so very little gas exchange happens in the tracheae
Runs into body and parallel to exoskeleton, along the body surface
What are tracheoles?
0.6 - 0.8μm diameter
Single elongated cell
No chitin supporting structure - permeable to gases
Spread throughout tissues of insect - between and into individual cells
Large surface area - site of gas exchange in insects
How is surface area increased in insects?
End of each tracheole has a small amount of liquid - where gases dissolve
Active muscles produce lactic acid - causes water to move out tracheoles and into tissues via osmosis
Retreating water exposes more surface area for gas exchange
When O2 is reduced, the fluid moves back into tracheoles carrying dissolved CO2 which diffuses out spiracles
What is a fish’s specialised gas exchange system?
4 pairs of gills in the pharynx - each supported by a bony arch
Along each arch is a double row of gill lamellae
Each gill lamellae has gill plates along each side
What is the gas exchange in fish?
Deoxygenated blood passes through capillaries that run though gill plates
O2 passes thought gill plates into capillaries
CO2 pass out of gill plates into water
Blood vessels carry oxygenated blood away from gills so maintaining the concentration gradient
How do fish take in water?
1) Mouth opens
2) Operculum closes at the opening at the back of the pharynx
3) Floor of mouth cavity is lowered
4) Volume inside mouth cavity increases and pressure inside cavity falls
5) Water rushes into mouth
How do fish let water pass out?
1) Mouth closes
2) Floor of mouth cavity raised
3) Volume inside mouth cavity decreases so pressure inside cavity rises, forcing water back over gills
4) Operculum opens
5) Water flows out
How does the counter current system work in fish?
Blood in capillaries flow in opposite direction to flow of water
Blood with low concentration of O2 passes into capillaries of gill lamellae
O2 rich blood now passes out gill lamellae and leaves the gills
Allows fish to receive 80% O2 extraction of O2 from water
What’s an advantage of the counter current system?
It always maintains a steep concentration gradient for O2
How do fish increase the efficiency of gas exchange?
Water passes over gills quickly - reduced amount of O2 and CO2 that can be exchanged
Tips of adjacent gill filaments overlap
Which increases resistance to flow of water
Flow of water slows over gill surfaces - more time for gas exchange to take place
What is transpiration?
movement of water through a plant - ground - (active transport) roots - xylem - leaves - stomata (diffusion)
