Year 12 - Gas exchange Flashcards
Describe and explain the movement of oxygen in an insect.
Oxygen used in aerobic respiration inside of cells.
Establishes an oxygen concentration gradient.
Spiracles open
Oxygen diffuses in through spiracles.
Spiracles close
Oxygen diffuses through the trachea into the tracheoles.
Delivered directly to respiring tissues.
Describe and explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange.
Tracheoles have thin walls so short diffusion distance to cells.
Highly branches so large surface area for gaseous exchange.
Fluid in the end of the tracheoles moves out into tissues during exercise so faster diffusion through the air to the gas exchange surface.
Body can be moved by muscles to move air (abdominal pumping) so maintains concentration gradient for oxygen and carbon dioxide.
Describe how the structure of the insect gas exchange system is adapted for efficient gas exchange and limits water loss
Gas exchange adaptions:
Spiracles open to allow diffusion of oxygen through spiracles, through tracheae and then through tracheoles.
Tracheoles are highly branches so large surface area
Tracheole walls are thin, highly branched and enter cells so short diffusion distance.
Tracheole permeable to oxygen
To limit water:
Exoskeleteon of insect is impermeable so reduce water loss.
Spiracles can close so no water loss
Hairs around spiracles reduce water loss.
Describe and explain the counter-current principle in gas exchange across a fish gill
Water and blood flow in opposite directions
Maintains concentration gradient of Oxygen
along entire length of lamellae/filament/gill
Oxygen concentration always higher in water than in blood.
Describe and explain three ways in which a fish’s gills system is adapted for efficient gas exchange
Many gill filaments and lamellae so large surface area
Thin epithelium of lamellae with capillary network so short diffusion distance between water and blood
Water and blood flow in opposite directions so that a concentration gradient is maintained across the entire length of lamellae
Describe and explain the movement of Carbon Dioxide into leaves
Mesophyll cells photosynthesise reducing concentration of CO2
CO2 diffuses from air spaces into the cells.
Creating concentration gradient of CO2, from higher concentration outside to lower concentration in air spaces.
Guard cells open stomata in light conditions
CO2 diffuses through stomata down concentration gradient
Suggest and explain how the features of a xerophytic plant help prevent water loss
Rolled leaves so ‘trap’ water vapour and water potential gradient decreased ->less transpiration
Spines/needles so reduces surface area to volume ratio ->less evaporation
Hairs so ‘trap’ water vapour decreasing water potential/concentration Gradient
Sunken Stomata in pits so ‘trap’ water vapour decreasing water potential/concentration gradient.
Thicker cuticle so increases diffusion distance.
Waxy layer so reduces evaporation/transpiration.
Fewer stomata so less surface area for transpiration
Describe how you could use an eyepiece graticule to determine the mean diameter of stomata
Measure using eye piece graticule
Calibrate eyepiece graticule against stage micrometre
Take a large number of repeat measurements to calculate mean
Describe and explain the features of the lungs that allow for efficient gaseous exchange
One cell thick in a single layer of cells so short diffusion pathway
Many alveoli gives a large surface area
Rich blood supply to maintain large concentration gradient
Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs
Oxygen moves through the trachea, bronchi, bronchioles to the alveoli down a pressure gradient.
Oxygen then moves by diffusion:
-Across the alveolar epithelium
-Across the capillary endothelium
Then binds with haemoglobin in a red blood cell.
Describe the gross structure of the human gas exchange system and how we breathe in and out.
Trachea -> bronchi -> bronchioles -> alveoli
Breathing in – diaphragm contracts and external intercostal muscles contract
Causes volume increase and pressure decrease in thoracic cavity so air moves in down a pressure gradient.
Breathing out - Diaphragm relaxes, external intercostal muscles relax and elastic tissue recoils.
Causes volume decrease and pressure increase in thoracic cavity so air moves out down a pressure gradient.
