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

• A. Smooth ER is found only in plant cells, while rough ER is found only in animal cells.
• B. Smooth ER is involved in lipid synthesis, while rough ER is associated with protein synthesis due to ribosomes on its surface.
• C. Smooth ER contains ribosomes on its surface, while rough ER does not.
• D. Smooth ER is responsible for DNA replication, while rough ER is involved in RNA transcription.

Answer: (B)

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. Identify the two types of ER: smooth ER and rough ER. The rough ER is characterized by the presence of ribosomes on its surface, giving it a 'rough' appearance under a microscope.
3. Recognize the primary function of rough ER, which is protein synthesis. The ribosomes attached to the rough ER are the sites where translation occurs, converting mRNA into polypeptide chains.
4. Understand the role of smooth ER, which lacks ribosomes on its surface. It is primarily involved in lipid synthesis, including phospholipids and steroids, and also plays a role in detoxification processes within the cell.
5. Clarify the misconception that smooth ER is found only in plant cells and rough ER only in animal cells. Both types of ER are present in both plant and animal cells, serving their respective functions in cellular metabolism.