11. Gas Exchange Flashcards
Why cant most cells rely on simple diffusion alone?
Most cells to far away from exchange surfaces and larger organisms rely on mass transport.
Single celled organisms rely on diffusion alone as they have a large SA:VOL ratio to meet their gas exchange however larger organisms cant rely on diffusion alone to supply O2 to all their cells for respiration so they have specialised gas exchange systems.
What does a larger SA:VOL ratio mean?
Higher metabolic rate (faster O2 diffusion, faster aerobic respiration, more ATP.)
What is Ficks Law?
Rate of diffusion (directly proportional) SAxConc Difference / distance of diffusion pathway.
Whats the gas exchange in insects?
Via Tracheal System directly to respiring tissues. O2 and CO2 diffuse in opposite directions to maintain a concentration gradient.
O2 enter from air through spiracles, into trachea and into tracheoles and directly into respiring tissues, down a conc gradient. O2 used up in respiration. When spiracles close gas exchange stops.
CO2 moves in opposite directions out insect into air as its produced in respiration in respiring tissues.
What are the adaptations of Gas Exchange in Insects? And how are some adapted to reduce water loss?
- Direct contact with tissue- short diffusion pathway.
- Tracheoles have thin walls- short diffusion pathway
- Respiring tissues use O2 and O2 enter through open spiracles - large concentration gradient.
- Tracheoles highly branched - large surface area.
- exoskeleton made of chitin- waxy cuticle reduce water loss
- smaller sa:vol ratio body shape- reduce water loss
- spiracles close and hairs around spiracles
Whats Gas Exchange in fish? And whats counter current mechanism?
Ventilation of H20 through gill swap H20 and O2. Circulation of blood swaps blood saturated with O2 with low O2 blood.
Each fish has 4 gills on each side and water moves in throigh mouth and out through gills. Each gill is made up of gill filaments and each filament has many lamellae.
Counter current mechanism blood and water flow in opposite directions through the gills, blood is always passing H2O with a higher conc of o2 so a conc gradient is maintained across the full length of the lamellae. So equilibrium is not reached.
How is the fish adapted for gas exchange?
Many lamellae - large SA
Counter current flow - maintain conc gradient
Thin lamellae cells - short diffusion pathway.
How does gas exchange in Dicotyledonous Plants?
- Palisade mesophyll cells photosynthesis using CO2 reducing CO2 conc in mesophyll cell. CO2 diffuses from air through stomata, through spongy mesophyll, palisade mesophyll cells.
- mesophyll cell produce O2 in photosynthesis, increasing the conc of O2 in the air spaces so O2 diffuse out of the leaf via stomata.
What adaptations does a leaf have and what factors affect the rate of gas exchange in plants?
Adaptations: stomata close at night to minimise water loss as less co2 is required at night. Air spaces: fast diffusion rate as less resistance. Thin: short diffusion pathway. Lots of stomata: large SA.
Factors: more stomata so more co2 uptake but more water loss by transpiration. Increased temp more KE increases evaporation of water. Reduce light stomata close. Increase humidity reduces water potential gradient decreasing transpiration .
How are Xerophyte plants adapted?
Live in low water environment so have:
- fewer stomata, less SA, less evaportation
- reduced leaves to spines : less stomata, less SA
- hairs : trap water and water potential gradient decreases.
- rolled leaves: trap water vapour decrease water potential gradient.
- stomata sunken in pits: trap water vapour and decrease water potential gradient.
- thick waxy cuticle: increases diffusion distance.
What are the features of an Alveolar Epithelium?
To enter blood O2 must diffuse through squamous alveolar epithelium and the smooth endothelium of capillary.
- only 1 cell thick-short diffusion pathway.
- contain flattened cells- (squamous epithelium) reduce diffusion distance.
- permeable cells photosynthesis using layer allows diffusion of O2 and CO2.
How is the alveoli adapted?
Thin epithelial lining walls- short diffusion pathway.
Many/Large SA- maximise gas exchange.
Good blood supply/well ventilated- maintain conc gradient
How to calc PVR?
Pulmonary ventilation rate = breathing rate x tidal volume.
PVR is the amount of air exchanged in 1 breathing cycle.
What is the breathing ventilation system? Whats route of air through lungs?
Trachea, Bronchus, Bronchioles, alveoli.
Inspiration(breathing in) : diaphragm contracts and flattens. External intercostal muscles contract and ribcage move up and out, increase volume in thorax, decrease pressure below atmospheric pressure. Air drawn into lungs.
Expiration (breathing out): diaphragm relax and moves upwards, external intercostal muscles relax (forced expiration internal intercostal muscles contract) ribcage move down and in, decrease volume in thorax and increases pressure above atmospheric. Air forced out of lungs.
Analysing data key thing?
SDs overlap = no sig diff
P=1 100% probability of that occurring by chance.
P=0 0% probability that occurring by chance
P=<0.5 is statistically significant
Correlation not linked with causal link.
Correlation -1 says theres a perfect negative relationship between 2 variable ( as one goes up other goes in opposite direction)
Correlation +1 perfect positive relationship
Correlation 0 no relationship
Null hypothesis: no correlation between variables.
