3.3 Transport in living organisms
Material exchange examples
● Respiration - take in oxygen, give out carbon dioxide
● Photosynthesis (green plants) - take in carbon dioxide, give out oxygen
● Nutrition (all living organisms, but in different forms) - take in “food” and other
“nutrients” including mineral ions
● Excretion - pass out waste metabolic materials (body not needed)
● Water (all living organisms) - both take in and pass out (depending on
requirements)
Unicellular/simple organisms: transport by simple diffusion
● Small size, short distance from outside to cytoplasm inside cell where metabolic
reactions take place
● ***Rate of diffusion over short distance is sufficient to supply materials and expel
waste materials through cell membrane
● ***Large surface area to volume ratio
Multicellular organisms
● ***Larger size, greater complexity, more problems of how materials are exchanged
with surroundings and how they are distributed inside organism
● Dependence on simple diffusion for material exchange, far too slow (as relatively
small surface area to volume ratio)
● Have transport systems for distribution of materials within organism
○ Have specialized exchange surfaces with large surface areas (e.g.:
alveoli)
● Plants
○ Root hair cells - provide enormous surface area, allowing entry of water
and mineral ions
○ Xylem - provides transport system carrying water and mineral ions *up*
plant to leaves and other parts of plant
○ Leaves - many stomata, provide large surface area through which gas
exchange takes place
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Material exchange examples
● Respiration - take in oxygen, give out carbon dioxide
● Photosynthesis (green plants) - take in carbon dioxide, give out oxygen
● Nutrition (all living organisms, but in different forms) - take in “food” and other
“nutrients” including mineral ions
● Excretion - pass out waste metabolic materials (body not needed)
● Water (all living organisms) - both take in and pass out (depending on
requirements)
Unicellular/simple organisms: transport by simple diffusion
● Small size, short distance from outside to cytoplasm inside cell where metabolic
reactions take place
● ***Rate of diffusion over short distance is sufficient to supply materials and expel
waste materials through cell membrane
● ***Large surface area to volume ratio
Multicellular organisms
● ***Larger size, greater complexity, more problems of how materials are exchanged
with surroundings and how they are distributed inside organism
● Dependence on simple diffusion for material exchange, far too slow (as relatively
small surface area to volume ratio)
● Have transport systems for distribution of materials within organism
○ Have specialized exchange surfaces with large surface areas (e.g.:
alveoli)
● Plants
○ Root hair cells - provide enormous surface area, allowing entry of water
and mineral ions
○ Xylem - provides transport system carrying water and mineral ions *up*
plant to leaves and other parts of plant
○ Leaves - many stomata, provide large surface area through which gas
exchange takes place
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