Humber Admissions Practice Test

What are ribosomes primarily made of?

1. DNA

2. Proteins

3. RNA

4. Phospholipids

The correct answer is: RNA

Ribosomes are primarily made of RNA, specifically ribosomal RNA (rRNA), which forms the core structure of ribosomes and is crucial for their function in protein synthesis. Alongside rRNA, ribosomes also contain proteins that help stabilize the RNA structure and assist in its function, but the defining component and the major structural element is indeed the RNA. This makes ribosomes unique cellular structures because they are not membrane-bound organelles and are fundamentally different from other cellular structures like the nucleus or mitochondria, where DNA predominates. While proteins are important for the overall ribosome structure and function, it is the rRNA that plays a central role in the ribosome's activity of translating messenger RNA (mRNA) into proteins in the process called translation. The other options do not accurately represent the primary composition of ribosomes. DNA is the genetic blueprint of the cell and is located mainly in the nucleus. Phospholipids are key components of cell membranes but do not constitute the ribosomes themselves. Understanding the primary role of RNA in ribosomes is essential for grasping how protein synthesis functions within cells.