Specialised Exchange Systems
- Created by: Jasmine
- Created on: 19-02-16 19:38
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- Specialised Exchange Systems
- Surface Area to Volume Ratio (SA:V)
- Smaller organisms have bigger surface area: volume ratios than bigger organisms
- Specialist Exchange Surfaces
- Single-celled Organisms
- Substances can diffuse directly into or out of the cell across the cell surface membrane
- The diffusion is quick as there is a short distance to travel as they have a very high SA:V
- Multicellular Organisms
- Slow for 3 reasons
- 1) Some cells are deep within the body- big distance to travel
- 2) Larger animals have a smaller SA:V- cannot exchange enough substances to supply a large volume when the SA is small
- 3) Multicellular have a higher metabolic rate compared to single-celled so they use O2 and glucose up faster
- Need specialised exchange surfaces eg alveoli in lungs
- Slow for 3 reasons
- Single-celled Organisms
- Special Features of Exchange Surfaces
- 1) A large SA- increases their efficiency eg root hair cells
- Roots have a large SA so it increases the rate of absorption of water by osmosis
- 2) They are thin- decrease distance of travel for exchange- one cell thick eg alveoli
- Alveolus have a single layer of cells called epithelium- decreases distance for O2 and CO2 to diffuse across- quicker diffusion
- 3) A good blood supply/ventilation-
- Alveoli have a large capillary network so each alveolus has their own blood supply- constantly takes O2 and gives CO2- helps maintain the concentration gradient
- 1) A large SA- increases their efficiency eg root hair cells
- Surface Area to Volume Ratio (SA:V)
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