What is the primary difference between the rough endoplasmic reticulum (ER) and the smooth endoplasmic reticulum (ER)?

• A. The rough ER is responsible for detoxification, while the smooth ER is responsible for calcium storage.
• B. The rough ER is found only in animal cells, while the smooth ER is found only in plant cells.
• C. The rough ER is involved in lipid synthesis, while the smooth ER is involved in protein synthesis.
• D. The rough ER has ribosomes on its surface, while the smooth ER does not.

Answer: (D)

Verified step by step guidance

1. Understand the structure and function of the endoplasmic reticulum (ER), which is an essential organelle in eukaryotic cells involved in the synthesis and processing of proteins and lipids.
2. Recognize that the ER is divided into two distinct regions: the rough ER and the smooth ER, each with unique functions and structural characteristics.
3. Identify the rough ER by its surface, which is studded with ribosomes. These ribosomes are the sites of protein synthesis, giving the rough ER its 'rough' appearance.
4. Contrast the smooth ER, which lacks ribosomes on its surface. The smooth ER is involved in lipid synthesis, detoxification processes, and calcium ion storage.
5. Conclude that the primary difference between the rough ER and the smooth ER is the presence of ribosomes on the rough ER, which are absent on the smooth ER.