Unit 3
Transport in cells.
How substances cross a cell's edge: diffusion, osmosis, active transport, and why surface area limits the size of cells.
Before this unit
- Cells and life
- Solutions Chemistry
The unit, lesson by lesson
Lessons
4 lessons · 22 practice questions · about 2 hours
Diffusion
The random motion of molecules, net movement from high concentration to low, dynamic equilibrium, and the effect of temperature.
Osmosis
When only the water can cross: which way it flows, what happens to the concentrations and volumes, and when the flow stops.
Cells in solutions
A red blood cell in hypotonic, isotonic and hypertonic solutions, why a plant cell does not burst, and active transport against the concentration gradient.
Surface area and volume
The square–cube law: when area grows as the square and volume as the cube, the surface area to volume ratio shrinks, which is why cells are small and big animals need lungs.