Biology Chapter 1 - Part 2
- Created by: elliebaxter
- Created on: 04-01-17 13:54
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- Biology Chapter 1 - Part 2
- Osmosis
- Movement of water across a partially permeable membrane from high water conc. to low water conc.
- 2 solutions have same conc. = isotonic Water with high conc. = hypertonic Water with low conc. = hypotonic
- When plant cells are placed in a hypertonic solution a lot of the water leaves the cell, the vacuole and cytoplasm shrink and the membrane pulls away from the cell wall (plasmolysed)
- Osmosis is important to maintain turgor (turgid shape) in plant cells
- Active transport
- Cells use active transport to absorb substances in short supply across a partially permeable membrane against the conc. gradient
- Active transport requires the energy released during respiration
- Examples of active transport: -Root cells absorb mineral ions from dilute solutions in the soil -glucose can be reabsorbed in the kidney tubules
- Exchanging materials
- Large organisms have many cells that are not in contact with their environment, so have special exchange surfaces to obtain the food and water they need
- Efficient exchange surfaces have: large surface area, thin walls, short diffusion path and efficient transport system ie. blood stream
- Plants have long thin roots and root hair cells increase surface area
- Leaves are flat and thin with internal air spaces and stomata to allow gases in and out of the leaves
- Exchange in the gut
- The villi line the inner surface of the small intestine and are the exchange surface for food molecules.
- Villi increase the surface area od small intestine
- The walls of the villi are very thin and there are many capillaries close to the wall
- The villi use both diffusion and active transport to absorb the product of digestion
- The villi line the inner surface of the small intestine and are the exchange surface for food molecules.
- Osmosis
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