CORE PRINCIPLES

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CORE PRINCIPLES
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ORGANISMS EXCHANGE MATERIALS WITH THEIR
ENVIRONMENT

• Exchange is mainly by diffusion
• Diffusion over the surface of a large organism is
  inefficient - small surface area volume ratio
• Larger organisms have specific systems containing
  exchange surfaces.
• These exchange surfaces are adapted to speed up
  diffusion

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Exchange Surfaces

• Mammals alveoli
• Bony fish gill plates on the lamellae
• Dicotyledonous plant leaves mesophyll cells

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Good exchange surfaces have

• A large surface area increases the SAvolume
  ratio
• A thin surface a shorter distance to travel
• A steep diffusion gradient a greater difference
  in concentration increases the rate of diffusion
  
• more molecules cross the surface
• per unit of time

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Mammals - the lungs remove about 5 of the
total oxygen in the air.ALVEOLI provide a good
exchange surface

• A large SA branched bronchioles
• millions of alveoli
• each alveolus is folded
• A thin permeable surface flattened
  cells of alveolus capillary walls
• two surfaces next to each other
• A diffusion gradient blood carries
  gases to from the surface
• ventilation brings air into
  removes air from the alveoli

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Bony fish gills remove 80 of the total
oxygen in waterGILL PLATES are ideal gas
exchange surfaces

• A large SA 4 pairs of gills with
  lamellae gill plates
• A thin permeable surface surface of the
  gill plates capillary wall
• made up of flattened cells
• total distance for diffusion 5um
• A diffusion gradient - circulation of the
  blood ventilation
• counter current flow
• lamellae held apart by water

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Plant leaves the large number of leaves
contribute to the gas exchange surface

• MESOPHYLL CELLS A large surface area each leaf
  is flat
• mesophyll cells separated with large
  air spaces between them
• A thin permeable membrane rarely
  more than 10 cell layers from top to bottom
  of a leaf
• to enter cells , gases only have to
  cross a cell wall cell surface membrane
• A diffusion gradient mesophyll cells use the
  gases for biochemical reactions

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Need to Know

• Ventilation of the lungs
• pathway of the air
• volume pressure changes
• structures involved
• Ventilation of the gills
• counter current flow
• volume pressure changes
• structures involved

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Digestion

• The structure of the gut wall 3 main layers

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Adaptations

• Oesophagus
• quick passage of food
• Stomach
• temporary storage
• mixing of contents
• some digestion
• Duodenum ileum
• Digestion
• absorption

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Enzyme activity - carbohydrate digestion

• Involves mouth, pancreas small intestine

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Enzyme activity - protein digestion

• Involves stomach, pancreas small intestine

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Enzyme activity - lipid digestion

• Involves the pancreas bile activity

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Absorption

• Glucose amino acids absorbed into blood
  capillaries
• partly by facilitated diffusion partly by
  active transport
• Fatty acids glycerol absorbed into the lacteals
  the blood capillaries
• by simple diffusion

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EXTRACELLULAR DIGESTION
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finally

• Testing for carbohydrase activity
• Starch-agar plates can be used to look for
  carbohydrase activity
• The size of the colourless area gives an
  indication of the activity of the enzyme
• The larger the colourless area, the more active
  the enzyme