Exchange And Transport Flashcards
Gas exchange insects
• Insects have spiracles and tracheae that branch into tracheoles
• Gasses (e.g. Oxygen) diffuse through the spiracles and the tracheae/tracheoles
• Tracheoles are very branched so have a large surface area and short diffusion pathway
• Tracheoles are penetrate respiring tissue so have a short diffusion distance
• Abdominal pumping allows more O2 to be brought into the tracheoles, but it is not a structure so is rarely brought up
Water loss insects
• Cuticle exoskeleton that
limits water loss
• Spiracles can close to
prevent water loss
• Hairs around spiracles to
prevent water loss
Gas exchange in fish/counter current flow
• Fish have gills with many gill filaments and lamella to increase the
surface area to volume ratio
• Single layer of cells in lamella so short diffusion pathway
• Blood flows in the opposite direction to water in a counter current
flow
• This maintains the diffusion gradient so O2 conc. Is always higher in
the water than the blood
• Diffusion occurs along the entire length of the lamellae/filament
Ventilation in mammals
• Inhalation: External intercostal muscles and
diaphragm contract internal intercostal muscles
relax
• Ribcage moves up and out diaphragm moves down
• Volume in the thorax increases so pressure
decreases and air moves in
• Exhalation: External intercostal muscles and
diaphragm relax internal intercostal muscles
contract
• Ribcage moves down and in diaphragm moves up
• Volume in the thorax decreases so pressure
increases and air moves out
Gas exchange in mammals
• Alveoli are a single layer of cells to reduce diffusion
distance
• Alveoli are branched so have
a large surface area
• Alveoli have a good blood supply so the oxygen diffusion pathway is maintained
Gas exchange in plants
• Plants have stomata to allow gases to
move in an out of the leaves
• Humidity – affects the diffusion gradient of
water
• Temperature – affects the KE of molecules
• Air movement – affects the diffusion
gradient all molecules
• Light intensity – can open and close
stomata (using guard cells), increases
photosynthesis affecting diffusion gradient
Oxygen cooperative binding to haemoglobin
• As O2 loads to oxygen, its binding cause the
haemoglobin to change shape
• This change of shape makes it easier for more
oxygen to load
• Until all the haem groups are occupied and the
haemoglobin is saturated (full)
• This is called co-operative binding
Bohr shift/CO2
• In exercising or organisms with high metabolism
• CO2 in tissues reduces the affinity of oxygen to
haemoglobin (it’s acidic/changes Hb shape)
• In tissues where there is lots of respiration the oxygen
is more easily unloaded – this makes the curve shift to
the right.
• This can replace used O2 easier
• The impact of CO2 is called the Bohr Shift
Shift to the left
Usually in low oxygen environments e.g. womb, high altitude, under water
1. Higher affinity for oxygen at low
ppO2
2. Oxygen associates/loads more
readily
3. More oxygen can bind where little
oxygen is available e.g foetus
Shift to the right
Usually in metabolically active organisms
e.g. mice or runners
1. Lower affinity of oxygen at higher
ppO2
2. Oxygen disassociates/unloads more
readily
3. More oxygen available in tissues for
More aerobic respiration
Transpiration
• Water evaporates from the leaves/transpiration
• Due to heat/kinetic energy from sunlight
• Water diffuses out of the stomata from a high water potential to low
• The diffusion of water causes tension in the xylem
• This is due to water potential gradient
• Cohesion tension forms a continuous column of water that is pulled through the xylem in a
transpiration stream
• Water’s adhesive properties aid the movement through the xylem
• Transpiration stream lowers water potential in the root cells
• Water is absorbed through the root hair cells by osmosis from a higher water potential to low.
Factors affecting transpiration
• Humidity – increases or decreases the water potential gradient
• Light intensity/stomata opening/no of stomata – more light more
photosynthesise, stomata open in the day close at night
• Temperature – increases kinetic energy, more diffusion
• Wind movement - increases or decreases the water potential gradient
Translocation/mass flow
• Sucrose (and other solutes) are
actively transported into
phloem (or co-transported with
H+) by companion cells
• This lowers the water potential
in the phloem and water moves
in by osmosis
• This creates high hydrostatic
pressure leading to mass flow
to respiring cells/storage organs
• Solutes/sucrose is unloaded
from the phloem by active
transport
