Organelles and Their Functions
Identify major organelles and explain how the nucleus, ribosomes, endomembrane system, mitochondria, chloroplasts, cytoskeleton, and vacuoles support cell function.
A lesson of Biology, in Cells and Cellular Processes, about 25 minutes.
Organelles and What They Do
By the end of this lesson, you will be able to name the organelles of an animal cell on a diagram, say what each one does, and explain why a cell needs its jobs kept in separate compartments at all.
A Cell Is a Factory with Rooms
A cell is not a bag of chemicals sloshing together. It is a workshop with rooms, and the rooms exist for a reason.
Respiration releases energy and produces acid. Protein synthesis needs a clean, controlled bench. Digestion of waste needs enzymes that would happily digest the cell itself. Run all three in one open space and each one ruins the others.
So the cell builds compartments, each wrapped in its own membrane, each held at its own conditions. Those compartments are the organelles, and every one of them is a room with a job.
The rule worth carrying through the whole topic:
Structure fits function. If you can see what an organelle looks like, you can usually work out what it does.
The Rooms, and Their Jobs
| Organelle | What it looks like | What it does |
|---|---|---|
| Nucleus | Large, round, its own double membrane | Holds the DNA and issues the instructions |
| Nucleolus | A dense spot inside the nucleus | Builds ribosomes |
| Mitochondrion | Oval, with folded inner membranes | Releases energy from glucose |
| Ribosome | Tiny dots, no membrane | Assembles proteins |
| Cell membrane | The boundary, two layers thick | Controls what enters and leaves |
| Cytoplasm | The fluid filling the rest | Where most reactions happen |
| Vacuole | A fluid-filled sac | Storage |
Read the shapes. A mitochondrion is folded because folding multiplies the surface area available for the reactions of respiration: the same volume, far more workbench. That is structure fitting function, and it is the answer to a surprising number of exam questions.
Label the Diagram: The Animal Cell
Each label goes on the part it names. Hover a slot to see which part it points at.
Sort It: Animal, Plant, or Both
The two decoys above are the point of this. A plant cell has everything an animal cell has, plus three things an animal cell never has.
<!-- SLATE_IF_STRONG: science.biology.cell-structure --> <!-- END_SLATE_IF_STRONG -->