GCSE Combined Science AQA - Transport in cells
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- Created on: 05-04-18 11:23
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- Transport in cells
- Diffusion is the spreading out of particles resulting in a net movement from an area of high concentration to an area of low concentration
- Examples include oxygen and CO2 in gas exchange, and excretion of urea into the kidney from plasma.
- The concentration gradient, the temperature and the membrane surface area all affect the rate of diffusion.
- A single celled organism has a large surface area to volume ratio, which allows sufficient transport of molecules into and out of the cell.
- A cell with a small surface area to volume ratio is able to diffuse molecules more efficiently.
- A single celled organism has a large surface area to volume ratio, which allows sufficient transport of molecules into and out of the cell.
- The effectiveness of an exchange surface can be increased by being ventilated, having a large surface area, having a thin membrane or having an efficient blood supply.
- The lungs can have a more effective exchange surface by having alveoli. This alveoli is ventilated as the person breathes, and has huge surface area and a large blood supply.
- The small intestine has villi on it, which also provide a larger surface area and a rich blood supply.
- Fish have to exchange oxygen and CO2 between blood and water through their gills.
- The gills have a rich blood supply.
- Plant roots have root hair cells which increase the surface area.
- Flat thin leaves, the presence of air pockets and the stomata all help a plant to have a larger surface area.
- The lungs can have a more effective exchange surface by having alveoli. This alveoli is ventilated as the person breathes, and has huge surface area and a large blood supply.
- Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
- If external concentration is the same as internal concentration, the solution is isotonic.
- If it is higher than the internal concentration, it is hypertonic
- If it is lower than the internal concentration, then it is hypotonic.
- If this happens, the cell is likely to burst.
- If this happens, the cell will release water and swell up.
- If it is lower than the internal concentration, then it is hypotonic.
- If it is higher than the internal concentration, it is hypertonic
- If external concentration is the same as internal concentration, the solution is isotonic.
- Active transport is the movement of substances from a dilute solution to a more concentrated solution, against the concentration gradient.
- It requires energy from respiration.
- In roots, active transport allows mineral ions to be absorbed into root hairs. Plants require ions for healthy growth.
- It also allows sugar molecules to be absorbed from the gut into the blood. These molecules are used for cell respiration.
- In roots, active transport allows mineral ions to be absorbed into root hairs. Plants require ions for healthy growth.
- It requires energy from respiration.
- Diffusion is across a cell membrane, osmosis is through a membrane, active transport is against a concentration gradient.
- Diffusion is the spreading out of particles resulting in a net movement from an area of high concentration to an area of low concentration
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