The table shows changes in the mean volume of animal cells placed in three solutions. The dissolved substances cannot cross the cell membranes.
Table
| Solution | Initial mean cell volume in arbitrary units | Final mean cell volume in arbitrary units |
|---|---|---|
| P | 100 | 118 |
| Q | 100 | 100 |
| R | 100 | 82 |
Which solution best maintains normal cell volume, and why?
P, because water enters faster than it leaves
Q, because there is no net movement of water
Q, because water cannot cross the cell membrane
R, because water leaves faster than it enters
44 exam-style questions on Edexcel GCSE Biology 7.3 Homeostasis and thermoregulation, covering 7.3.1 Importance of a constant internal environment, 7.3.2 Importance of homeostasis, 7.3.3a Thermoregulation via the skin and hypothalamus, and 7.3.3b Vasoconstriction and vasodilation in thermoregulation. Each one has a worked solution and a mark scheme showing where the marks go.