Exchange Services
- Created by: Abc312
- Created on: 18-04-18 20:39
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- Exchanging Substances
- Surface area to volume ratio
- How easy it is for an organism to exchange substances depends on the surface area to volume ratio
- The bigger an organism the smaller the surface area compared to the volume.
- A single-celled organism has a large surface area compared to the volume and substances can diffuse directly into the cell.
- Multi-cellular organisms have a smaller surface area compared to the volume
- This means specially adapted exchange surfaces are needed for efficient diffusion
- How easy it is for an organism to exchange substances depends on the surface area to volume ratio
- Alveoli in the lungs
- The job of the lungs is to transfer oxygen into the blood and remove carbon dioxide from it.
- The alveoli are air sacs where gas exchange takes place.
- They are specialised to maximise diffusion
- They have a very large surface area
- A moist lining for dissolving gases
- Very thin walls for a short diffusion path.
- A good blood supply
- Villi in the small intestine
- The small intestine is covered in millions of villi.
- They are adapted to absorb digested food quicker.
- The cell walls are only one cell thick.
- They have a very good blood supply.
- The villi increase the surface area of the intestine to increase the surface area to volume ratio and speed up diffusion.
- Structure of Leaves
- The stomata are holes on the underside of the leaf.
- They allow carbon dioxide to diffuse into the leaf.
- Oxygen and water vapour diffuse out of the stomata
- The stomata are controlled by guard cells which close the stomata if the plant loses too much water.
- This stops the plant from wilting and dying.
- The flat shape of the leaf increases the area.
- The walls of the cells inside the leaf are also exchange surfaces.
- The air spaces inside the cell increase the area of the surface so there is more chance for carbon dioxide to get into the cells.
- The stomata are holes on the underside of the leaf.
- Gills in fish
- Gills are where gas exchange happens in fish
- Water (containing oxygen) enters the fish through the mouth and passes out through the gills.
- When this happens the oxygen diffuses from the water into the blood and carbon dioxide goes from the blood to the water.
- Water (containing oxygen) enters the fish through the mouth and passes out through the gills.
- Gills are made from thin plates called gill filaments.
- This increases the surface area for gas exchange.
- The gill filaments are covered in lamellae.
- They increase the surface area even further,
- They have lots of blood capillaries to speed up diffusion.
- They have a thin surface layer to minimise the distance that the gases need to diffuse,
- Blood flows across the lamellae in one direction and water in the opposite direction.
- This maintains a large concentration gradient.
- Gills are where gas exchange happens in fish
- Surface area to volume ratio
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