Biology Regents Practice Exam

In which part of the cell does protein synthesis occur?

1. Nucleus.

2. Ribosome.

3. Mitochondria.

4. Endoplasmic reticulum.

The correct answer is: Ribosome.

Protein synthesis occurs at the ribosome, which is a complex molecular machine found within all living cells. The ribosome is responsible for translating the genetic information encoded in messenger RNA (mRNA) into a sequence of amino acids, thereby forming proteins. This process, known as translation, is a crucial step in gene expression, allowing cells to produce the proteins necessary for various functions and structures. While protein synthesis also involves other cellular components, such as the nucleus – where DNA is transcribed into mRNA – and the endoplasmic reticulum, which plays a role in protein folding and modification, the actual assembly of proteins into polypeptide chains occurs at the ribosomes. Therefore, identifying the ribosome as the site of protein synthesis highlights its essential role in this vital biological process.