Eukaryotic Translation (Protein Synthesis), Animation.

Summary

The translation process involves three main stages: initiation, elongation, and termination. It begins when the small ribosomal subunit binds to the initiator tRNA carrying methionine, scanning for the start codon AUG. During elongation, tRNAs enter the ribosome, matching their anticodons with mRNA codons, facilitating peptide bond formation. This cycle continues until a stop codon is reached during termination, where a release factor cleaves the bond between the polypeptide and tRNA, resulting in the release of the newly formed polypeptide and disassembly of the ribosome for another translation round.

Takeaways

• 😀 Initiation begins when the small ribosomal subunit binds to the initiator tRNA carrying methionine.
• 😀 The complex formed attaches to the cap structure at the 5' end of mRNA and scans for the start codon AUG.
• 😀 Several initiation factors mediate the attachment and scanning process.
• 😀 The ribosome has three sites: A-site (entry for new tRNA), P-site (holds growing polypeptide), and E-site (exit for used tRNA).
• 😀 The initiator tRNA is positioned in the P-site at the start of translation.
• 😀 During elongation, a new tRNA carrying an amino acid enters the A-site of the ribosome.
• 😀 The anticodon of the incoming tRNA is matched against the mRNA codon in the A-site, ensuring accuracy through proofreading.
• 😀 A peptide bond forms between adjacent amino acids as the ribosome moves one triplet forward on the mRNA.
• 😀 The process of elongation continues until a stop codon enters the A-site.
• 😀 Termination occurs when a release factor binds to the stop codon, leading to the release of the polypeptide and disassembly of the ribosome.

Q & A

What initiates the translation process?

The translation process begins with the binding of the small ribosomal subunit to the initiator tRNA carrying methionine, which then attaches to the cap structure at the 5' end of the mRNA and scans for the start codon AUG.

What role do initiation factors play in translation?

Initiation factors help facilitate the binding of the ribosomal subunits and tRNA to the mRNA, ensuring the proper assembly of the translation initiation complex.

What are the three sites on the ribosome, and what are their functions?

The three sites on the ribosome are: A-site (entry site for aminoacyl-tRNA), P-site (occupied by peptidyl-tRNA carrying the growing polypeptide chain), and E-site (exit site for tRNA after it delivers the amino acid).

How does the ribosome ensure the correct tRNA is matched with the mRNA codon?

The ribosome matches the anticodon of the incoming tRNA with the mRNA codon in the A-site. Incorrect tRNAs are rejected through a proofreading mechanism.

What occurs when the correct aminoacyl-tRNA enters the A-site?

When the correct aminoacyl-tRNA enters the A-site, a peptide bond is formed between the amino acids of the tRNAs in the A-site and P-site.

What happens to the tRNA in the P-site after a peptide bond is formed?

The tRNA in the P-site releases its amino acid to the tRNA in the A-site and becomes empty, allowing the ribosome to move forward.

What triggers the termination of the translation process?

Termination occurs when one of the three stop codons (UAA, UAG, or UGA) reaches the A-site, where no matching tRNA can fit.

What is the role of the release factor in termination?

The release factor binds to the stop codon in the A-site, catalyzing the cleavage of the bond between the polypeptide and the tRNA, leading to the release of the polypeptide.

What happens to the ribosome after the termination of translation?

After termination, the ribosome disassociates into its subunits, which can be reused for another round of translation.

What is the significance of the translation process in biology?

Translation is crucial for protein synthesis, enabling cells to produce the proteins necessary for various biological functions based on the genetic information encoded in mRNA.