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Unit 9: Structure of a cell

About this unit

You, my friend, are made up of cells. Lots and lots of them. Some of them are eukaryotic (human), but many more of them are prokaryotic, thanks to the friendly bacteria of your gut, skin, and other body systems. Jump in to learn more about prokaryotic and eukaryotic cells and the complex and beautiful structures inside of them.

Test your understanding of cell structure!


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Start your cellular journey the right way: with some history and some microscopy! Here, we'll learn more about how cells were discovered, how they can be observed, and how big they are in comparison to other very small things.
Here's a question: what's the difference between you and a bacterium? Probably quite a lot of things! At the cellular level, though, some of the key differences include a cell nucleus and membrane-bound organelles, which you have (and the bacterium lacks). Here, we'll look in detail at the differences between prokaryotes and eukaryotes.
Join us on a voyage through some of the specialized compartments and structures of eukaryotic cells. From the rolling folds of the endoplasmic reticulum to the majestic fibers of the microtubule cytoskeleton, it's a trip you won't regret!
We've spent a lot of time looking at what's inside a cell. But what about the stuff on the outside? Here, we'll look at the extracellular matrix of animal cells and the cell wall of plant cells, as well as the junctions that hold cells together.