Building on Grade 9: go deeper into organelle structure and function, the fluid mosaic model of the cell membrane, and how substances move across membranes by diffusion, osmosis and active transport.
Our understanding of cells only became possible with the invention of the microscope. Early lens-based instruments let scientists first see cells; modern light microscopes use glass lenses and visible light, while electron microscopes use beams of electrons to reveal much finer detail — including the internal organelles you'll learn about below.
The cell membrane is described by the fluid mosaic model: a flexible ("fluid") double layer of phospholipids with proteins floating in it like tiles in a mosaic. This structure controls what can move into and out of the cell.
| Process | Description | Energy needed? |
|---|---|---|
| Diffusion | Movement of particles from a high to a low concentration, until evenly spread | No |
| Osmosis | Diffusion of water molecules specifically, across a selectively permeable membrane | No |
| Active transport | Movement of particles against the concentration gradient (low to high) | Yes (uses ATP) |
Beyond the basics you learnt in Grade 9 (membrane, cytoplasm, nucleus, mitochondria, ribosomes), Grade 10 introduces more organelles and their roles:
Watch particles move across a membrane. In Diffusion mode, all particles can cross freely. In Osmosis mode, only water (blue) can cross — solute (orange) stays put — and water moves to balance the concentration.
| Sucrose concentration (mol/dm³) | Initial mass (g) | Final mass (g) |
|---|---|---|
| 0.0 (pure water) | 5.00 | 5.75 |
| 0.2 | 5.00 | 5.30 |
| 0.4 | 5.00 | 5.00 |
| 0.6 | 5.00 | 4.55 |
| 0.8 | 5.00 | 4.20 |