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

• A. Smooth ER is involved in protein synthesis, while rough ER is involved in lipid synthesis.
• B. Smooth ER lacks ribosomes on its surface, while rough ER has ribosomes attached to its surface.
• C. Smooth ER is responsible for DNA replication, while rough ER is responsible for RNA transcription.
• D. Smooth ER is found only in plant cells, while rough ER is found only in animal cells.

Answer: (B)

Verified step by step guidance

1. Understand the structure and function of the endoplasmic reticulum (ER) in eukaryotic cells. The ER is a network of membranes within the cell that plays a crucial role in the synthesis and transport of proteins and lipids.
2. Differentiate between the two types of ER: smooth ER and rough ER. The primary structural difference is the presence or absence of ribosomes on their surfaces.
3. Recognize that rough ER has ribosomes attached to its surface, which gives it a 'rough' appearance under a microscope. These ribosomes are sites of protein synthesis, making rough ER integral to the production of proteins.
4. Identify the smooth ER, which lacks ribosomes on its surface, giving it a 'smooth' appearance. Smooth ER is involved in lipid synthesis, detoxification processes, and calcium ion storage, among other functions.
5. Clarify misconceptions: Smooth ER is not involved in protein synthesis, nor is it responsible for DNA replication. Both smooth and rough ER are found in various eukaryotic cells, not limited to plant or animal cells.