Algonquin College Health Program Assessment (AC-HPAT) Practice Exam

Where are proteins primarily modified and sorted within the cell?

1. Endoplasmic reticulum

2. Golgi apparatus

3. Nucleus

4. Ribosomes

The correct answer is: Golgi apparatus

The Golgi apparatus is the primary location within the cell where proteins are modified and sorted. Once proteins are synthesized in the ribosomes and translocated into the endoplasmic reticulum (ER), they undergo initial folding and modifications in the ER. However, their final modifications and sorting into transport vesicles occur in the Golgi apparatus. The Golgi apparatus receives proteins from the ER and processes them through a series of enzymes that perform various modifications, such as glycosylation or phosphorylation. Once these modifications are complete, the Golgi sorts the proteins and packages them into vesicles for delivery to their designated locations, either inside the cell or for secretion outside of the cell. This function is crucial for the proper distribution and function of proteins within the cell. In contrast, the endoplasmic reticulum is mainly involved in the synthesis and preliminary modification of proteins but does not perform the final sorting. The nucleus is primarily responsible for housing genetic material and is not directly involved in protein modification. Ribosomes are the sites of protein synthesis, not modification or sorting. Thus, the Golgi apparatus is specifically designed for the critical roles of modification and sorting, making it the correct answer.