Question

Where are you likely to find a tRNA with only one amino acid that is not a Met (corresponding to the start codon)?

1) In the cytoplasm
2) In the nucleus
3) In the ribosome
4) In the endoplasmic reticulum

Answer 1

tRNA molecules carrying amino acids other than methionine are typically found within the ribosome during the elongation phase of protein synthesis in the cytoplasm.

Step-by-step explanation:

The location where you are likely to find a tRNA carrying an amino acid that is not methionine (Met) would be within the ribosome. During the process of translation, tRNAs carry amino acids to the ribosome, which assembles them into a polypeptide chain, based on the sequence of codons in the mRNA. Specifically, this occurs in the cytoplasm, as ribosomes can either be free in the cytoplasm or attached to the endoplasmic reticulum, forming what's known as the rough ER.


However, the actual site of the growing polypeptide chain, where tRNAs bring amino acids for incorporation, is the ribosome itself. Therefore, after initiation, only the initiator tRNA carrying methionine aligns at the P-site of the ribosome. Once the polypeptide elongation phase begins, you can find tRNAs carrying different amino acids at the A site of the ribosome just before they are added to the growing polypeptide chain.