Ribosomes are the site of which process?

• A. Lipid synthesis
• B. Protein synthesis
• C. DNA replication
• D. Energy production

Answer: (B)

Ribosomes are where protein synthesis happens, translating mRNA into a growing polypeptide chain. They are made of ribosomal RNA and proteins and come in two subunits that join around the mRNA. As tRNA brings amino acids to the ribosome, codons on the mRNA are read and peptide bonds form between adjacent amino acids, creating the protein. In eukaryotes, ribosomes can be free in the cytoplasm or attached to the rough endoplasmic reticulum; in prokaryotes they’re free in the cytosol.

Lipid synthesis happens mainly in the smooth endoplasmic reticulum and associated membranes, not at ribosomes specifically. Energy production occurs in mitochondria (and chloroplasts in plants) through processes like oxidative phosphorylation. DNA replication occurs in the nucleus with DNA polymerases.