Where does protein synthesis occur within a cell?

Protein synthesis primarily occurs at ribosomes, which are the cellular structures responsible for translating the genetic code carried by messenger RNA (mRNA) into polypeptide chains, culminating in protein formation. Ribosomes can either be free-floating in the cytosol or attached to the rough endoplasmic reticulum, and they play a crucial role in assembling amino acids in the order specified by the mRNA sequence.

While the nucleus is essential for DNA transcription, where genetic information is copied into mRNA, it does not participate directly in protein synthesis. The smooth endoplasmic reticulum is involved in lipid synthesis and detoxification processes rather than directly synthesizing proteins. The Golgi apparatus functions primarily in the modification, sorting, and packaging of proteins produced in the rough endoplasmic reticulum but does not engage in the synthesis itself. Thus, ribosomes are correctly identified as the site where protein synthesis takes place, making this the correct answer.