Amino Acids and tRNA Function in Protein Synthesis

Introduction to Amino Acids and tRNA

• Amino Acids: The basic building blocks of proteins, coded by codons in mRNA.

• tRNA Function: tRNA (transfer RNA) is responsible for bringing the correct amino acid to the ribosome during protein synthesis.

  • Each tRNA has a specific anticodon that pairs with complementary codons on the mRNA.

Codons and Anticodons

• Codon: A sequence of three nucleotides on mRNA that codes for a specific amino acid.

  • Example: The codon "UUU" codes for phenylalanine.

• Anticodon: A sequence of three nucleotides on tRNA that pairs with the codon on mRNA.

  • Needs to be complementary for correct amino acid incorporation.

• Hydrogen Bonding:

  • Hydrogen bonds form between the codon and anticodon, ensuring that the correct amino acid is brought in.

  • If bonding does not occur, the amino acid will not be incorporated into the protein chain.

Importance of tRNA Structure

• Three-Dimensional Structure: The shape of tRNA is crucial for its function. It is a single-stranded molecule that folds into a specific shape due to hydrogen bonding within the strand.

  • Contains an anticodon on one end and an amino acid attachment site on the other end.

• Diversity of tRNA:

  • There are multiple tRNAs, each with different anticodons corresponding to the various amino acids needed during protein synthesis.

Initiation of Translation

• Steps:

  1. Binding of mRNA to Ribosome:

  • The messenger RNA binds to the small subunit of the ribosome.

  1. Initiator tRNA:

  • The first tRNA (which carries methionine) binds to the start codon on mRNA.

  • The anticodon of the tRNA pairs with the start codon, initiating the formation of a polypeptide chain.

  1. Large Subunit Attachment:

  • After the tRNA binds, the large subunit of the ribosome joins the complex, allowing for peptide bond formation.

Peptide Bond Formation

• Dipeptide Formation:

  • The process creates a peptide bond between two amino acids, releasing water through dehydration synthesis.

  • This bond forms between the carboxyl group of one amino acid (C-terminus) and the amino group of the next amino acid (N-terminus).

• C-Terminus and N-Terminus:

  • The C-Terminus (carboxyl end) is where subsequent amino acids are added.

  • The N-Terminus (amino end) is the start of the polypeptide chain.

Summary

• tRNA and the process of translation are vital for protein synthesis, ensuring that amino acids are assembled in the correct order as dictated by the mRNA codons. Proper hydrogen bonding between codons and anticodons is crucial for accuracy in protein formation, starting with methionine and proceeding along the ribosome to create functional proteins.