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

• A. Rough ER has ribosomes attached to its surface, while smooth ER does not.
• B. Rough ER is located near the cell membrane, while smooth ER is located near the nucleus.
• C. Rough ER is found only in animal cells, while smooth ER is found only in plant cells.
• D. Rough ER is involved in lipid synthesis, while smooth ER is involved in protein synthesis.

Answer: (A)

Verified step by step guidance

1. Begin by understanding the basic structure and function of the endoplasmic reticulum (ER), which is an essential organelle in eukaryotic cells involved in the synthesis and transport of proteins and lipids.
2. Identify the rough endoplasmic reticulum (RER) by its characteristic feature: the presence of ribosomes attached to its cytoplasmic surface, giving it a 'rough' appearance under a microscope.
3. Contrast this with the smooth endoplasmic reticulum (SER), which lacks ribosomes on its surface, resulting in a 'smooth' appearance.
4. Clarify the functional differences: Rough ER is primarily involved in the synthesis of proteins, especially those destined for secretion or for use in the cell membrane, due to the presence of ribosomes. Smooth ER, on the other hand, is involved in lipid synthesis and metabolism, detoxification processes, and calcium ion storage.
5. Correct any misconceptions: Both rough and smooth ER are found in both plant and animal cells, and their location within the cell is not strictly near the cell membrane or nucleus. Rough ER is typically located near the nucleus and the Golgi apparatus, facilitating the transport of synthesized proteins.