What cellular structure synthesizes proteins from amino acids?

The synthesis of proteins from amino acids primarily occurs at ribosomes, which are essential cellular structures found in all living cells. Ribosomes translate messenger RNA (mRNA) into polypeptide chains, a process that assembles amino acids in the order specified by the genetic code. As ribosomes read the mRNA, they facilitate the bonding of amino acids to form a protein through a series of steps that involve transfer RNA (tRNA) bringing the appropriate amino acids to the ribosome for incorporation into the growing protein chain.

While other structures in the cell, such as the endoplasmic reticulum and Golgi apparatus, are involved in processing and transporting proteins after they are synthesized, ribosomes themselves are the key sites where the actual translation of genetic information into functional proteins takes place. Hence, ribosomes are often referred to as the "protein factories" of the cell due to their crucial role in protein synthesis.