**Core Concept:** Protein synthesis is the process by which cells produce proteins from amino acid building blocks based on genetic instructions encoded in messenger RNA (mRNA). Messenger RNA carries the genetic information from the nucleus to the ribosomes in the cytoplasm, where proteins are synthesized.

**Why the Correct Answer is Right:** The correct answer to the question about the RNA molecule removed during protein synthesis is **Option D:** the 5' untranslated region (5'UTR) of mRNA. During translation, the ribosome reads the mRNA sequence and synthesizes the protein based on the genetic code. The 5'UTR contains regulatory elements that control the initiation of translation and the rate of protein synthesis.

**Why Each Wrong Option is Incorrect:** Here are the explanations for each incorrect option:

A. **Option A:** 3'UTR (3' untranslated region) - This is the part of the mRNA molecule that follows the coding sequence, but it is not removed during protein synthesis.

B. **Option B:** Codons - These are the triplet nucleotide sequences that encode specific amino acids in the mRNA sequence. Codons are not removed during protein synthesis, they are the basic building blocks of the genetic code.

C. **Option C:** Amino acids - These are the building blocks of proteins but not removed during protein synthesis. Amino acids are incorporated into the growing polypeptide chain by the ribosome during translation.

D. **Option D:** 5'UTR (5' untranslated region) - This is the part of the mRNA molecule that precedes the coding sequence. The 5'UTR is removed during protein synthesis as it contains regulatory elements that control the initiation of translation and the rate of protein synthesis.

**Clinical Pearl:** Protein synthesis is a critical process in cells, as it plays a vital role in maintaining cell function, growth, and development. Understanding the different regions of the mRNA molecule and their functions is essential for medical students and healthcare professionals alike.