What do ribosomes contain in addition to proteins?

Ribosomes are complex macromolecular machines essential for protein synthesis in all living cells. In addition to proteins, ribosomes primarily contain ribosomal RNA (rRNA). This type of RNA is a fundamental component of ribosomes, forming both the structural framework and serving crucial functional roles during translation.

rRNA molecules help facilitate the binding of messenger RNA (mRNA) and transfer RNA (tRNA) to the ribosome during protein synthesis, enabling the ribosome to translate the genetic code into a polypeptide chain. The presence of rRNA is vital because it catalyzes the formation of peptide bonds between amino acids, thereby playing an integral role in the assembly of proteins.

While messenger RNA (mRNA) is crucial for providing the genetic blueprint for protein synthesis and transfer RNA (tRNA) is involved in delivering the appropriate amino acids to the ribosome, the question specifically asks what ribosomes contain. Ribosomal RNA is the correct answer as it is a persistent and essential structural component of the ribosomes themselves, in contrast to mRNA and tRNA, which are transiently associated with ribosomes during the process of translation. Additionally, ribosomes do not contain DNA, as they are not involved in the storage or replication of genetic information.