Importance Of Protein Synthesis

Protein synthesis is involved in gene expression. Gene expression is the process of DNA that controls protein synthesis. Genes code for certain proteins that are created by DNA transcription and translation (Reece, et al. 334). This happens by using an mRNA template to specify the order of amino acids. Protein synthesis starts on the free ribosomes within the cytosol. The signal sequence that initiates the process is located at the N-terminal end of the polypeptide chain. Different codons along the mRNA are translated into amino acids as a ribosome moves along it. Then, tRNAs act as adapters to control the movement of amino acids to the ribosome. This occurs through the base pairings of the codons of the mRNA and and anti-codon of the tRNA. The ribosome then forms the peptide bonds between the amino acids of the polypeptide chain (Erster Lect. 21). Creation of the polypeptide chain can be divided into three stages of initiation, elongation, and termination. Each stage requires the aid of protein factors. For certain parts initiation and elongation, energy may also be needed.

This answer is incorrect. Termination is the last stage of translation and it is a stage that requires energy. Elongation ends when it encounters a stop codon in the mRNA that has reached the A site of a ribosome. A release factor is then binded to the stop codon which causes a water molecule to be added instead of an amino acid. This would break the bond between the polypeptide chain and the tRNA on the P site so that the polypeptide can be released to the exit tunnel. The rest of the translation assembly is broken down which requires energy from the hydrolysis of two GTP molecules (Reece, et al. 351).

Choice D. This answer is correct. Each of the three stages of protein synthesis explained above require large amounts of energy, there is no answer choice that does not require energy. Initiation, elongation and termination all require GTP molecules as a source of energy in the