In which part of the cell does protein synthesis primarily occur?

• A. Nucleus
• B. Mitochondria
• C. Ribosomes
• D. Golgi apparatus

Answer: (C)

Protein synthesis primarily occurs at ribosomes, which are complex molecular machines found in all living cells. Ribosomes translate the genetic information carried by messenger RNA (mRNA) into polypeptide chains, which then fold into functional proteins.

The process begins when mRNA, synthesized during transcription in the nucleus, is transported to the ribosomes in the cytoplasm. There, ribosomes read the sequence of nucleotides in the mRNA and use transfer RNA (tRNA) to bring in the appropriate amino acids in a sequence that corresponds to the genetic code. This process is crucial for creating proteins that are essential for various cellular functions, including enzyme activity, structural roles, and signaling.

Other cellular structures have different roles in the context of protein handling. The nucleus is where DNA is transcribed into mRNA but does not participate in the actual synthesis of proteins. Mitochondria are primarily involved in energy production through cellular respiration, although they have their own ribosomes and can synthesize some proteins necessary for their functions. The Golgi apparatus is involved in modifying, sorting, and packaging proteins for secretion or use within the cell, but it does not synthesize proteins directly.