Which of the following sequences represents the order in which a protein made in the rough endoplasmic reticulum might move through the endomembrane system?

• A. Lysosome → plasma membrane
• B. Golgi apparatus → mitochondria
• C. Plasma membrane → nuclear envelope
• D. Nuclear envelope → lysosome
• E. Golgi apparatus → lysosome

Answer: (E)

Verified step by step guidance

1. Understand the role of the rough endoplasmic reticulum (RER) in protein synthesis. Proteins synthesized in the RER are typically destined for secretion, incorporation into the cell membrane, or for use in lysosomes.
2. Recognize that after synthesis in the RER, proteins are transported to the Golgi apparatus. The Golgi apparatus modifies, sorts, and packages proteins for their specific destinations.
3. Identify that proteins destined for lysosomes are tagged with specific markers in the Golgi apparatus, which directs them to lysosomes.
4. Consider the options provided and eliminate those that do not follow the typical pathway of protein movement through the endomembrane system. For example, proteins do not typically move from the Golgi apparatus to mitochondria or from the plasma membrane to the nuclear envelope.
5. Conclude that the correct sequence for a protein moving through the endomembrane system, starting from the rough endoplasmic reticulum, is: Golgi apparatus → lysosome.