Which organelle is the site of protein synthesis in cells and is found throughout the cytoplasm?

• A. Ribosome
• B. Nucleus
• C. Golgi apparatus
• D. Endoplasmic Reticulum

Answer: (A)

Protein synthesis happens at ribosomes, which are small RNA–protein machines that translate the instructions in mRNA into a chain of amino acids. These ribosomes can float freely in the cytoplasm or be attached to the rough endoplasmic reticulum, giving many proteins immediate access to the cytosol or membranes as they’re made. The nucleus houses DNA and is the site of transcription, not translation. The Golgi apparatus then modifies and ships proteins, while the endoplasmic reticulum, especially the rough ER, provides a site for synthesizing proteins destined for secretion or membranes, but the actual site of protein synthesis dispersed in the cytoplasm is the ribosome itself.