Question

What role does peptidyl transferase play in protein synthesis? A. It transports the initiator aminoacyl-tRNA complex. B. It helps the ribosome to advance three nucleotides along the mRNA in the 5? to 3? direction. C. It holds the protein in its tertiary structure. D. It catalyzes the formation of a peptide bond.

Short answer

D. It catalyzes the formation of a peptide bond.

Step-by-step solution

Understand Protein Synthesis

To answer this question, first, understand the basics of protein synthesis. Protein synthesis consists of transcription and translation. Translation involves the ribosome reading mRNA and assembling amino acids into a polypeptide chain.

Identify Peptidyl Transferase

Peptidyl transferase is an enzymatic activity found in the ribosome. It's responsible for catalyzing a key step during translation.

Determine Peptidyl Transferase Function

Peptidyl transferase's specific role in translation is to catalyze the formation of peptide bonds between the amino acids being added to the growing polypeptide chain.

Match with Given Options

Review the options provided: A, B, C, and D. Option D, 'It catalyzes the formation of a peptide bond,' matches perfectly with the known function of peptidyl transferase.

Key concepts

Protein Synthesis

Protein synthesis is a fundamental biological process that creates proteins necessary for the structure, function, and regulation of the body's cells, tissues, and organs. It can be broken down into two main stages: transcription and translation.

• Transcription - This is the first stage where the information in a gene's DNA is transferred to messenger RNA (mRNA) in the nucleus.
• Translation - During this second stage, the mRNA is decoded by the ribosome to produce a specific polypeptide or protein.

Understanding protein synthesis is key to comprehending how genes control the traits and functions of organisms.

Translation

Translation is the process where the genetic code carried by mRNA is translated into a sequence of amino acids to form a polypeptide chain. This takes place in the ribosome, a cellular organelle. The ribosome reads the mRNA in sets of three nucleotides called codons. Each codon specifies a specific amino acid.

• Initiation - The ribosome assembles around the target mRNA. The first tRNA is attached at the start codon.
• Elongation - The ribosome travels down the mRNA, reading codons and bringing corresponding tRNAs charged with amino acids.
• Termination - When a stop codon is reached, translation ends and the polypeptide is released.

By understanding translation, one can appreciate how proteins are exactly synthesized according to the genetic instructions.

Peptide Bond Formation

Peptide bond formation is a crucial step in protein synthesis, linking amino acids together to form a polypeptide chain. This bond forms between the carboxyl group of one amino acid and the amino group of another, releasing a molecule of water (H₂O).

• Peptidyl Transferase - An enzyme with ribosomal activity, peptidyl transferase catalyzes this bond formation during translation.
• Ribosome - The ribosome is the molecular machine that facilitates the formation of peptide bonds.
• Amino Acids - The building blocks of proteins, which are linked together by peptide bonds in a specific sequence ordained by mRNA.

This chemical reaction is crucial for building the primary structure of proteins, setting the stage for their eventual folding into functional forms.

Ribosomal Enzymatic Activity

Ribosomal enzymatic activity is the series of chemical reactions carried out by the ribosome, including the critical role of peptidyl transferase. The ribosome itself is composed of ribosomal RNA (rRNA) and proteins that collectively contribute to its catalytic activity.

• Peptidyl Transferase Center - This is the active site within the ribosome responsible for peptide bond formation.
• RNA Component - The rRNA in the ribosome plays a direct role in recognizing mRNA and tRNAs as well as catalyzing bond formation.
• Catalytic Efficiency - The enzymatic activity of the ribosome ensures that the process of translation is both rapid and accurate.

Understanding the ribosome's enzymatic activity helps us appreciate the molecular details of how proteins are constructed at the cellular level.