Every living thing is made of cells, every cell comes from another cell, and a cell is the smallest thing that is alive. That’s cell theory. But a cell isn’t a blob with labels. Every part has a job, and its shape gives the job away. Turn this one, slice it open, take it apart, and see for yourself.
This is an animal cell, blown up so it fills the screen. A real one is about a fiftieth of a millimetre across. Tap any part to fly to it.
Electron microscopes (from the 1940s on) use beams of electrons instead of light, and show parts far too small for any lens: the folds inside a mitochondrion, the ER, single ribosomes.
Or pick one from the list below. Each part you look at gets ticked off.
Cell wall and chloroplasts aren’t in an animal cell. You’ll find them in chapter 2.
A plant can’t walk to its food, and it has no bones. It stands in one spot in the sun for its whole life. So would its cells need different parts?
Switch to the plant cell and tap the three things a plant cell has that the animal cell didn’t.
| Part | Animal | Plant | Why a plant needs it |
|---|
Everything else (nucleus, membrane, cytoplasm, mitochondria) is in both. Same factory, three upgrades for a life of standing still in the sun.
Here is one mitochondrion, cut in half. The energy-releasing work happens on its inner layer, so the more inner layer there is, the more energy it can release at once. Unfold it and see what you lose.
A chloroplast is packed with stacks of flat green discs. The discs catch light, and the chloroplast uses that energy to build sugar. Flip the light and watch.
light energy + carbon dioxide + water → sugar + oxygen
The light is off. Nothing is being made.
A stomach cell makes a digestive protein and has to send it outside. Tap the stops in order, in the 3D cell or in the list.
Answer by tapping the part on the cell (or in the list below).
Folds for more surface. A wall for standing still. A tank for pressure. A gate for choosing what comes in. Every part has a job, and its shape gives the job away.
Tap a name to select it, same as tapping it in 3D. Works with a keyboard and screen readers.