AQA GCSE Biology unit 3 notes on exchange materials

A Brief table showing the details of exchanging materials.

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  • Created on: 25-05-09 23:59
Preview of AQA GCSE Biology unit 3 notes on exchange materials

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System Diagram Distance Surface Area Concn Gradient Additional
Capillary walls one cell Many alveoli make up Breathing in and out RBCs lots of
thick very large surface removes CO2 rich air, haemoglobin to carry
Alveolar walls one cell area 160m2 approx brings in O2 rich air lots of oxygen
Lungs thick Flow of blood past Capillaries thin so RBCs
Cells that make up Greater area for alveoli takes away very close to alveolar
walls are flat/ thin gas exchange oxygenated blood walls
short diffusion maintains gradient CO2 carried in blood
distance plasma
Walls of villi only one Small intestine very Good blood supply and Passage of food
cell thick long (approx 7m) lacteals take away through small intestine
Walls of capillaries Villi and microvilli products of digestion takes a long time ­
Gut/ Digestion only one cells provide very large and maintain the increased time for
surface area concentration gradient absorption
short diffusion Greater area for
distance absorption of
products of digestion
Leaf thin ­ short Spongy M cells No ventilation mechn;
distant between air loosely packed
and PM Concn grads maintained
Plants Thin cell walls
Lots of stomata by gases being used/
widely space so air produced (proportions
can get to all parts of depend on conditions and
leaf relative p/s to

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Lamellae walls only one Lots of filaments on Constant flow of fresh Tips of filaments
cell thick stacks and lots of water (by movement or overlap ­ slow down
Capillary walls only one lamellae on filaments ventilation) ­ means 02 flow of water ­ more
Fish cell thick gives very large concn kept high time for gas exchange
surface area Good blood supply takes In some fish, blood and
short diffusion oxygenated blood away ­ water flow in opposite
distance maintains gradient directions to maintain…read more


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