Kaplan Nursing Entrance Practice Exam

Which organelle is primarily involved in protein synthesis?

1. Nucleus

2. Mitochondria

3. Ribosome

4. Lysosome

The correct answer is: Ribosome

The ribosome is the organelle primarily responsible for protein synthesis. This is a critical process in the cell, as proteins perform a vast array of functions necessary for cellular structure and regulation. Ribosomes assemble amino acids into polypeptides according to the sequence of messenger RNA (mRNA), which serves as a template derived from DNA in the nucleus. While the nucleus plays a role in the overall process of protein synthesis by housing DNA, which contains the genetic instructions for making proteins, it does not directly synthesize proteins. Instead, it is involved in transcription, where the information in DNA is transcribed to mRNA. The mitochondria are primarily known as the powerhouse of the cell, generating energy in the form of ATP, and they have a role in cellular respiration rather than protein synthesis. Lysosomes, on the other hand, are involved in the degradation of waste materials and cellular digestion. They do not play a direct role in synthesizing proteins. Thus, the ribosome's key role in translating the genetic code into functional proteins makes it the correct answer for this question about protein synthesis.