Cells are a strange unit to teach because the whole subject is invisible. Students cannot see the thing we are talking about, so it stays abstract — a poster of labeled blobs they memorize on Thursday and forget by Monday. The turning point in my classroom is always the same moment: when a kid realizes that they are made of these things, trillions of them, all working right now.
Once cells stop being a diagram and start being them, organelles stop being vocabulary and become a tour of jobs that keep something alive. Here is how I teach it for MS-LS1-1 and MS-LS1-2, building from the big idea of cell theory down to the specific parts and how their structure fits their function.
What is cell theory, and why start there?
Cell theory has three parts: all living things are made of one or more cells, the cell is the basic unit of life, and all cells come from existing cells. I start here because it frames MS-LS1-1 — the evidence that living things are built from cells, whether they are a single cell or many. Everything else in the unit hangs on this one foundation.
I lead with the evidence, not the definition. Once students accept that an organism is either one cell or a community of many, the question becomes natural: if cells are the unit of life, what is inside one that lets it stay alive?
What are the main organelles and what do they do?
Organelles are the working parts of a cell, each with a job. The nucleus controls the cell and holds its DNA, the cell membrane controls what enters and leaves, and the cytoplasm is the gel-like fluid everything sits in. Mitochondria release energy through cellular respiration, ribosomes make proteins, and the vacuole stores materials.
- Nucleus: controls the cell and holds its DNA.
- Cell membrane: controls what enters and leaves the cell.
- Cytoplasm: the gel-like fluid that fills the cell and holds the organelles.
- Mitochondria: release energy the cell can use through cellular respiration.
- Ribosomes: build proteins.
- Vacuole: stores water, food, and other materials; especially large in plant cells.
What is the difference between plant and animal cells?
Plant and animal cells are both eukaryotic and share most organelles — nucleus, membrane, cytoplasm, mitochondria, ribosomes, and vacuoles. Plant cells have two extra structures animal cells lack: a cell wall for support and structure, and chloroplasts that carry out photosynthesis. Those additions are why plants can stand upright and make their own food.
I tie each difference to a job. A plant cannot run to find food or lean on a skeleton, so structure and the cell wall handle support and chloroplasts handle making food. Framing it this way keeps MS-LS1-2 front and center: structure relates to function.
What is the difference between prokaryotic and eukaryotic cells?
The key difference is the nucleus. Prokaryotic cells, like bacteria, have no nucleus and no membrane-bound organelles — their DNA floats freely in the cytoplasm. Eukaryotic cells, which make up plants, animals, fungi, and protists, have a nucleus and membrane-bound organelles. This connects to MS-LS1-1: organisms can be a single cell or many cells.
I keep the dividing line simple and memorable: prokaryotes have no nucleus, eukaryotes do. Bacteria are the everyday prokaryote students already know, which gives the abstract term something real to attach to.
How do I build a cell model for MS-LS1-2?
MS-LS1-2 asks students to develop a model showing the parts of a cell and their functions. I have them build a model — diagram, edible, or 3D — and label not just what each organelle is but what it does. The function is the point; a model that names parts without explaining their jobs misses the standard.
After the modeling, I use a low-stakes review so students apply the parts instead of re-reading them. An escape room works well: each puzzle hands students a cell scenario and asks which organelle is responsible and why. They are too busy solving to notice they are reviewing.
Start with the idea that students are made of cells, tie every organelle to a job, and a unit that usually feels like memorizing a diagram turns into a tour of how life actually works.