What part of the cell is responsible for making proteins?

The ribosomes are the primary sites for protein synthesis within a cell. They read the messenger RNA (mRNA) that is transcribed from DNA in the nucleus, translating the genetic code into polypeptide chains, which then fold into functional proteins. Ribosomes can be found either free-floating in the cytoplasm or attached to the endoplasmic reticulum, which further helps in the synthesis and transportation of proteins.

While the nucleus plays a crucial role in genetic information storage and the initial steps of protein synthesis by producing mRNA, it does not directly make the proteins. The mitochondria are primarily involved in energy production and metabolism, while the endoplasmic reticulum has roles in protein and lipid synthesis but does so in conjunction with ribosomes. Thus, ribosomes are specifically responsible for the actual process of assembling amino acids into proteins.