OCR GCSE Biology Practice Exam 2026 – Comprehensive All-in-One Guide to Exam Success

Protein synthesis primarily occurs at the ribosome, which is often referred to as the "protein factory" of the cell. Ribosomes are small, complex structures composed of ribosomal RNA and proteins. They can either be found floating freely in the cytoplasm or attached to the endoplasmic reticulum, which is then called rough ER.

During protein synthesis, the process begins with transcription in the nucleus, where DNA is converted into messenger RNA (mRNA). This mRNA then travels to the ribosome, where it serves as a template for assembling amino acids into a polypeptide chain, ultimately leading to the formation of proteins. The ribosomes facilitate the translation process by reading the sequences of nucleotide bases on the mRNA and matching them with the corresponding amino acids carried by transfer RNA (tRNA).

In summary, while the nucleus is crucial for the initial transcription step and the endoplasmic reticulum plays a role in folding and modifying proteins, the actual synthesis—where the amino acids are linked together to form proteins—takes place at the ribosome.