146504
Description
Flashcards by eimearkelly3, updated more than 1 year ago
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Created by eimearkelly3
over 11 years ago
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| Question | Answer |
| A selectively permeable membrane | Allows some but not all substances to pass through |
| A semi-permeable artificial membrane used in the lab | Visking tubing |
| The use of energy to move molecules against a concentration gradient | Active transport |
| Diffusion | The spreading out of molecules from a region of high concentration to a region of low concentration. This is due to the kinetic energy of molecules and is therefore passive (does not require external energy). Diffusion is said to take place across a concentration gradient. |
| Adaptations of the alveoli to improve gas exchange | Large surface area (numerous alveoli) Thin walls Moist |
| Solvent | A liquid that dissolves other substances e.g. water |
| Solute | A substance that is dissolved e.g. salt or sugar dissolved in water |
| Solution | Mixture of solvent and solute e.g. salty water |
| Osmosis | The diffusion of water molecules across a semi-permeable membrane from a region of high water concentration to a region of low water concentration. (Also passive) |
| Hypertonic solution | Lower concentration of water than the other solution |
| Hypotonic solution | Higher concentration of water than the other solution |
| Isotonic solution | Equal concentration of water to the other solution |
| Animal cells in an isotonic solution | Remain the same, water moves in and out at the same rate. |
| Animal cells in a hypotonic solution | Gain water due to osmosis (Amoeba have contractile vacuoles to prevent bursting) |
| Animal cells in a hypertonic solution | Lose water due to osmosis, cells shrivels and dies (crenation) |
| Examples of osmosis | Absorption of water by the plant roots Re-absorption of water by the proximal and distal convoluted tubules of the kidneys The turgor of plant cells gives support to non-woody cells Opening and closing of stomata Absorption of water by the stomach, small intestine, and colon. Flow of water in the amoeba |
| Plant cells in an isotonic solution | Remain the same |
| Plant cells in a hypotonic solution | Gain water due to osmosis, becomes turgid |
| Turgor / turgor pressure | The pressure of the cytoplasm and the vacuole against the cell wall of a plant. |
| Plant cells in a hypertonic solution | Lose water due to osmosis, the vacuole shrivel and move away from the cell wall. Becomes flaccid (limp) and wilts. The cell is then said to be plasmolysed. |
| The reversal of plasmolysis | Deplasmolysis --> put the cells in a hypotonic solution |
| Cell wall of bacteria | Polysacccharides / protein |
| Cell walls of fungi | Chitin |
| Food preservation by osmosis | Salting bacon/fish or preserving fruit and jam by adding sugar (hypertonic solution --> cell loses water --> enzymes no longer work --> cell dies) |
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