Humber Admissions Practice Test

Which structure is primarily involved in protein synthesis?

1. Smooth ER

2. Nucleus

3. Rough ER

4. Golgi apparatus

The correct answer is: Rough ER

The rough endoplasmic reticulum (Rough ER) is primarily involved in protein synthesis due to its structure and function. It is studded with ribosomes on its cytoplasmic surface, which gives it a "rough" appearance under a microscope. These ribosomes are the sites where protein synthesis occurs, translating messenger RNA (mRNA) into polypeptide chains. Once synthesized, proteins enter the lumen of the Rough ER, where they undergo folding and modifications necessary for their functionality. The Rough ER is essential for the production of proteins that are either secreted from the cell, incorporated into the cell's plasma membrane, or sent to organelles. This specialized role highlights the significance of the Rough ER in the overall process of synthesizing proteins within the cell. In contrast, while the nucleus is responsible for housing the genetic material and facilitating the transcription of DNA to mRNA, it is not directly involved in the translation process of protein synthesis. The Golgi apparatus plays a critical role in modifying, sorting, and packaging proteins for secretion or delivery to other organelles, but it does not synthesize proteins itself. The smooth endoplasmic reticulum is primarily involved in lipid synthesis and detoxification processes rather than protein synthesis.