Where are proteins synthesized in the cell?

Proteins are synthesized in the ribosomes, which are the cellular machinery responsible for translating messenger RNA (mRNA) into polypeptide chains, ultimately folding them into functional proteins. Ribosomes can be found either floating freely in the cytoplasm or bound to the endoplasmic reticulum, which contributes to the rough appearance and is involved in the synthesis of proteins destined for secretion or for use in the cell membrane.

The nucleus, while crucial for the transcription of DNA into mRNA, does not participate directly in protein synthesis. Instead, it is the site where the genetic information is stored and where the initial steps of gene expression occur. Mitochondria, known as the powerhouse of the cell, primarily focus on energy production through ATP synthesis, and while they do have some ribosomes for synthesizing a small number of their own proteins, they are not the main site for protein synthesis. Lysosomes, on the other hand, are involved in the breakdown of cellular waste and do not play a role in synthesizing proteins. Thus, ribosomes are the correct and primary location for protein synthesis in the cell.