Which structure in the cell is responsible for protein synthesis?

• A. Nucleus
• B. Ribosome
• C. Endoplasmic reticulum
• D. Golgi apparatus

Answer: (B)

The ribosome is the structure in the cell that is primarily responsible for protein synthesis. Ribosomes can be found free-floating in the cytoplasm or attached to the endoplasmic reticulum, forming rough ER. They read messenger RNA (mRNA) sequences, which are transcribed from DNA, and use that information to assemble amino acids into polypeptides, ultimately folding into functional proteins.

While the nucleus plays a crucial role in the synthesis of mRNA (the transcription of DNA), it does not directly synthesize proteins. The endoplasmic reticulum, particularly rough ER, assists in the production and folding of proteins and the Golgi apparatus is involved in modifying, sorting, and packaging proteins for secretion or delivery to other organelles. However, the ribosome is the actual site where amino acids are linked together to form proteins, making it the key structure responsible for the process of protein synthesis itself.