The cell organelle responsible for building proteins that is found in prokaryote cells because it's not surrounded by a membrane is the ribosome.

Here's why:

* Protein Synthesis: Ribosomes are the sites of protein synthesis. They read the genetic code from messenger RNA (mRNA) and use that information to assemble amino acids into protein chains.

* No Membrane: Prokaryotic cells lack membrane-bound organelles like the nucleus, endoplasmic reticulum, and Golgi apparatus. Ribosomes, being relatively simple structures, can exist freely in the cytoplasm of prokaryotes without a membrane.

* Presence in All Cells: Both prokaryotes and eukaryotes have ribosomes, highlighting their fundamental role in cellular function.

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