What is the primary function of ribosomes in a cell?

Ribosomes play a critical role in the process of protein synthesis, which is the primary function that defines them. These small structures can be found either floating freely in the cytoplasm or attached to the endoplasmic reticulum in eukaryotic cells. Their main task is to translate messenger RNA (mRNA) into polypeptide chains, which eventually fold into functional proteins. This translation process is vital for the cell, as proteins are essential for numerous cellular functions, including acting as enzymes, structural components, and signaling molecules.

In the context of cellular activities, while energy production primarily occurs in organelles like mitochondria, and DNA replication is facilitated by specialized enzymes and does not involve ribosomes, the key distinction lies in the ribosomes’ sole responsibility for synthesizing proteins from amino acids in accordance with the genetic information encoded in DNA. Thus, the correct answer accurately captures the fundamental role of ribosomes within the cell's machinery of life.