Movement of molecules in and out of cells
- Created by: Uswa
- Created on: 23-03-13 14:33
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- Movement of molecules in and out of cells
- Dissolved Substances
- Dissolved substances move by diffusion and by active transport.
- OSMOSIS
- Is the diffusion of water molecules from a dilute to a more concentrated solution, through a partially permeable membrane that allows passage of water molecules.
- Water often moves across boundaries by osmosis.
- Differences in concentration of the solutions INSIDE and OUTSIDE of a cell--> cause water to move into our out of cells by osmosis.
- Soft drinks
- Many soft drinks contain WATER, SUGAR and IONS.
- Most drinks contain SUGARS to replace the sugar used in ENERGY RELEASE during the activity
- They contain WATER and IONS to replace the ones lost during SWEATING.
- If water and ions aren't replaced, ion/water balance of body is disturbed
- And cells don't work effectively
- Active Transport
- Substances are sometimes absorbed against a concentration gradient
- Needs use of energy from respiration and is called ACTIVE TRANSPORT.
- Allows cells to absorb ions from very dilute solutions
- Substances are sometimes absorbed against a concentration gradient
- Adaptations
- Gas and solute exchange surfaces are adapted to maximise effectiveness.
- Effectiveness of exchange surface is increased by
- Having a large surface area
- Being thin- Short diffusion path
- [In animals]
- Having efficient and constant blood supply
- Being ventilated (For GASEOUS exchange)
- Size & complexity of an organism increases the difficulty of exchanging materials
- Dissolved Substances
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