What is the role of ribosomes in the cell?

• A. Ribosomes are RNA-protein complexes that synthesize proteins by translating mRNA.
• B. Ribosomes are DNA-protein complexes that replicate DNA.
• C. They modify proteins in the Golgi apparatus.
• D. They are lipid assemblies in mitochondria.

Answer: (A)

Ribosomes are RNA-protein machines that translate the genetic message in mRNA into a protein. They consist of two subunits that come together on an mRNA, read codons, and recruit tRNAs carrying the appropriate amino acids to form a growing polypeptide chain connected by peptide bonds. In cells, free ribosomes make cytosolic proteins, while ribosomes attached to the rough endoplasmic reticulum synthesize proteins destined for secretion or membranes. They’re built from ribosomal RNA and proteins and use energy during initiation and elongation to place amino acids correctly. This role is distinct from DNA replication, Golgi modification, or lipid structures in mitochondria.