In what part of the molecule are the radioactive amino acids located if protein synthesis is already underway when they are introduced?

In what part of the molecule are the radioactive amino acids located if protein synthesis is already underway when they are introduced?

• A. Only in the center of the molecule
• B. Evenly throughout the entire molecule
• C. Concentrated at the N-terminus
• D. At one end of the molecule

Answer: (D)

During protein synthesis, amino acids are added sequentially to a growing polypeptide chain. When radioactive amino acids are introduced while this process is ongoing, they would be incorporated at the end of the molecule where synthesis is taking place, specifically at the C-terminus. All new amino acids are linked to the free amino group of the growing polypeptide. As a result, the most recent amino acids incorporated, including the radioactive ones, would be located at the end of the protein chain. This process reflects the directional nature of protein synthesis, which occurs from the N-terminus (start) to the C-terminus (end). Therefore, the radioactive amino acids would not be found concentrated at the N-terminus, centrally located in the molecule, or evenly distributed. Instead, they would cluster at the end where the addition occurs, indicating that they are incorporated sequentially into the already synthesized portion.

During protein synthesis, amino acids are added sequentially to a growing polypeptide chain. When radioactive amino acids are introduced while this process is ongoing, they would be incorporated at the end of the molecule where synthesis is taking place, specifically at the C-terminus. All new amino acids are linked to the free amino group of the growing polypeptide. As a result, the most recent amino acids incorporated, including the radioactive ones, would be located at the end of the protein chain.

This process reflects the directional nature of protein synthesis, which occurs from the N-terminus (start) to the C-terminus (end). Therefore, the radioactive amino acids would not be found concentrated at the N-terminus, centrally located in the molecule, or evenly distributed. Instead, they would cluster at the end where the addition occurs, indicating that they are incorporated sequentially into the already synthesized portion.