What is a cell?
A cell is the smallest unit of life that can survive on its own. Think of it like a single brick — every living thing, from a tiny bacterium to a human being, is built from cells.
Two Main Types of Cells
There are two big groups of cells, and the easiest way to tell them apart is one thing: does it have a nucleus?
- Prokaryotic cells — no nucleus. Their genetic material floats freely inside the cell. Bacteria are the classic example.
- Eukaryotic cells — have a nucleus that keeps the genetic material safely wrapped up. Plant cells, animal cells, and fungi are all eukaryotic.
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The Main Parts of a Eukaryotic Cell (and what they do)
Think of a cell like a tiny factory. Every part (called an organelle) has one job:
- Nucleus — the control room. Holds the DNA and directs everything the cell does.
- Mitochondria — the power plant. Breaks down food to release energy (this is why it's called "the powerhouse of the cell").
- Cell membrane — the security gate. Controls what enters and leaves the cell.
- Cytoplasm — the factory floor. The jelly-like substance where all the cell's activities happen.
- Ribosomes — the assembly line. Builds proteins.
- Cell wall (plants only) — an extra rigid outer layer for support. Animal cells don't have this.
Quick Way to Remember
If you see a rigid cell wall and a big vacuole (a storage bag) — it's a plant cell. If you don't see those — it's an animal cell.
Why This Matters for Your Exams
Past questions in this course often ask you to:
- Identify whether a described cell is prokaryotic or eukaryotic.
- List the differences between plant and animal cells.
- Match an organelle to its function.
Go through the diagram above until you can redraw it from memory — that alone answers most classification questions.