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| Frage | Antworten |
| What are the factors that affect permeability/structure? | Temperature Solvents |
| What happens to the cell membrane as the temperature increases? | Increasing temperature increases kinetic energy, meaning that phospholipids vibrate more. This makes the bilayer more unstable, making the membrane more 'leaky', allowing more molecules through that would not normally be able to BUT! Once a certain temperature has been reached, the membrane breaks |
| What happens to the cell membrane at temperatures below 0°C? | The phospholipids don't have much energy, so they can't move very much. They are packed closely together and the membrane is rigid. BUT! Channel/carrier proteins in the membrane denature, increasing the permeability. Ice crystals may form and pierce the membrane, making it highly permeable when it thaws |
| What happens to the cell membrane at temperatures between 0°C and 45°C? | The phospholipids can move around and are not packed as tightly together - the membrane is partially permeable. As the temperature increases, the phospholipids move more because they have more kinetic energy |
| What happens to the cell membrane at temperatures above 45°C? | The phospholipid bilayer starts to melt and the membrane becomes more permeable. Water inside the cell expands, putting pressure on the membrane. Channel/carrier proteins in the membrane denature so they cannot control what enters or leaves the cell - this increases permeability |
| How does the presence of organic solvents affect cell membrane permeability? | Organic solvents damage cell membranes as they dissolve lipids |
| Name two examples of organic solvents which damage cell membranes | Acetone Ethanol |
| How does increasing the concentration of organic solvents affect cell membrane permeability? | Increasing the concentration of the solvent will also increase membrane permeability |
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