Humber Admissions Practice Test 2025 - Free Practice Questions and Study Guide for Humber College Admissions

The synthesis of proteins is fundamentally dependent on ribosomes, which are the cellular machinery responsible for translating messenger RNA (mRNA) into protein chains. These ribosomes can be found either free-floating in the cytoplasm or attached to the rough endoplasmic reticulum (rough ER).

The presence of ribosomes on the rough ER is what gives it a "rough" appearance, and this association is vital for the synthesis of proteins that are either secreted from the cell, incorporated into the cell's membranes, or sent to organelles. Once ribosomes start translating the mRNA, they facilitate the assembly of amino acids in the correct sequence, forming polypeptides that will fold into functional proteins.

The other components listed, while important in their own right, do not play a direct role in the synthesis of proteins. The nucleolus is involved in ribosome production but does not synthesize proteins itself. The nuclear membrane protects the nucleus and regulates the movement of materials in and out of it, without being involved directly in the synthesis of proteins. Lysosomes are primarily responsible for digestion and waste processing within the cell and do not participate in protein synthesis. Therefore, ribosomes are the key players in protein synthesis in association with the rough endoplasmic ret