A secretory cell would be most abundant in which structure involved in protein synthesis?

• A. Endoplasmic reticulum
• B. Ribosomes
• C. Golgi apparatus
• D. Lysosomes

Answer: (B)

Proteins for secretion are made by the cell’s protein-synthesis machines. Those machines are ribosomes, which translate genetic instructions into polypeptides. In secretory cells, there are many ribosomes to handle the large volume of protein production, and these ribosomes often sit on the rough endoplasmic reticulum to begin folding and directing the proteins into the secretory pathway. That abundance of ribosomes explains why this structure is most characteristic of a secretory cell. The endoplasmic reticulum itself participates in synthesis and folding, the Golgi packages and ships proteins, and lysosomes break down materials, but the primary driver of high secretory output is the availability of ribosomes to carry out the translation step.