The cellular organelle composed of protein and RNA responsible for the synthesis of soluble proteins is the ribosome.

Here's why:

* Protein and RNA Composition: Ribosomes are made up of ribosomal RNA (rRNA) and proteins.

* 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 polypeptide chains, which fold into functional proteins.

* Soluble Proteins: Ribosomes produce both soluble and membrane-bound proteins. Soluble proteins are those that function in the cytoplasm or other aqueous compartments within the cell.

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