The diagram below shows the rough endoplasmic reticulum of a cell as seen under the...

This question focuses on cell structure and function. The rough endoplasmic reticulum (RER) is characterized by the presence of small, dark granules attached to its surface. These granules are ribosomes. Ribosomes are the cellular structures responsible for protein synthesis, as they translate messenger RNA into amino acid chains. The presence of ribosomes gives the rough endoplasmic reticulum its “rough” appearance under an electron microscope. Mitochondria are involved in energy production, centrosomes play a role in cell division, and chromosomes contain genetic material within the nucleus. None of these structures are responsible for protein synthesis on the surface of the RER. The NEX Science exam frequently includes diagrams requiring students to identify organelles and link them to their functions. Recognizing ribosomes as the site of protein synthesis is a fundamental concept in cell biology.