Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

Which sequence correctly orders the parts involved in protein synthesis, packaging, and export?

1. Golgi complex → ribosome → endoplasmic reticulum → cell membrane

2. Ribosome → cell membrane → Golgi complex → endoplasmic reticulum

3. Ribosome → endoplasmic reticulum → Golgi complex → cell membrane

4. Endoplasmic reticulum → Golgi complex → ribosome → cell membrane

The correct answer is: Ribosome → endoplasmic reticulum → Golgi complex → cell membrane

The sequence that correctly orders the parts involved in protein synthesis, packaging, and export is ribosome → endoplasmic reticulum → Golgi complex → cell membrane. This order reflects the actual flow of protein synthesis and processing within the cell. Ribosomes are the cellular structures where protein synthesis begins, translating messenger RNA (mRNA) into polypeptide chains. Once proteins are synthesized, they are often translated into the rough endoplasmic reticulum (ER), which is where they undergo initial folding and structural modifications. Following their synthesis and initial processing in the ER, proteins are transported to the Golgi complex. The Golgi apparatus serves as a processing center where proteins are further modified, sorted, and packaged into vesicles for export. Finally, these vesicles fuse with the cell membrane, allowing for the secretion of proteins outside the cell or their integration into the membrane. This sequence illustrates the sequential nature of these cellular processes, highlighting the critical roles each component plays in ensuring that proteins are correctly synthesized, modified, and exported.