Which of the following is synthesized in the rough endoplasmic reticulum?

• A. Lipids for membrane synthesis
• B. Proteins destined for secretion
• C. Cholesterol for steroid hormone production
• D. Glycogen for energy storage

Answer: (B)

Verified step by step guidance

1. Understand the function of the rough endoplasmic reticulum (RER): The RER is studded with ribosomes, which are the sites of protein synthesis. This structure is primarily involved in the synthesis of proteins, especially those that are to be secreted from the cell, incorporated into the cell's plasma membrane, or sent to an organelle.
2. Differentiate between the functions of the rough and smooth endoplasmic reticulum: The smooth endoplasmic reticulum (SER) is involved in lipid synthesis, metabolism of carbohydrates, and detoxification of drugs and poisons. In contrast, the RER is involved in protein synthesis due to the presence of ribosomes.
3. Analyze the options given: Lipids for membrane synthesis are typically synthesized in the smooth endoplasmic reticulum, not the rough endoplasmic reticulum.
4. Consider the synthesis of cholesterol and glycogen: Cholesterol for steroid hormone production is also synthesized in the smooth endoplasmic reticulum, while glycogen is stored in the cytoplasm and not synthesized in the endoplasmic reticulum.
5. Conclude with the correct function of the RER: Proteins destined for secretion are synthesized in the rough endoplasmic reticulum, as it is equipped with ribosomes necessary for protein synthesis.