tRNA (Transfer RNA) in Protein Synthesis
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Questions and Answers

What is the primary function of the large 60S subunit in the process of translation?

  • To synthesize the polypeptide chain (correct)
  • To recruit the small ribosomal subunit and tRNA
  • To bind to the 5' end of the mRNA strand
  • To read the mRNA nucleotides in groups of three

    • What is the purpose of the P site on the ribosome?

  • To hold a tRNA that carries a growing polypeptide (correct)
  • To bind to the mRNA codons
  • To release the completed polypeptide chain
  • To accept an incoming tRNA bound to an amino acid

    • What is the result of the elongation step of translation?

  • The initiation of transcription
  • The recruitment of the small ribosomal subunit
  • The formation of a peptide bond between amino acids (correct)
  • The separation of the ribosome from the mRNA strand

    • What is the purpose of the anticodon on the tRNA?

    <p>To bind to the mRNA codons</p> Signup and view all the answers

    What is the function of the stop codon in the mRNA?

    <p>To terminate the translation process</p> Signup and view all the answers

    The small 40S subunit of the human ribosome contains a 28S RNA with 4700 nucleotides.

    <p>False</p> Signup and view all the answers

    During translation, the tRNA carrying the first amino acid in the protein is always bound to the amino acid methionine (Met).

    <p>True</p> Signup and view all the answers

    The ribosome travels along the mRNA strand from the 3' end to the 5' end during elongation.

    <p>False</p> Signup and view all the answers

    The E site on the ribosome is where the tRNA binds to the codon on the mRNA.

    <p>False</p> Signup and view all the answers

    The sequence of amino acids in the polypeptide chain is determined by the sequence of codons in the tRNA.

    <p>False</p> Signup and view all the answers

    Study Notes

    tRNA Structure and Function

    • tRNA is a single-stranded molecule with bases U, A, C, and G.
    • It has two attachment sites: one for amino acids and one for anti-codons.
    • tRNA acts as an adapter molecule, linking amino acids to their specific codons in mRNA.
    • Aminoacylation of tRNA is the first step in protein synthesis.
    • tRNA is specific to each amino acid.

    Ribosome Structure

    • Prokaryotic (bacterial) ribosomes have a sedimentation constant of 70S (2.7×10^6 Daltons) with small subunit 30S and large subunit 50S.
    • Eukaryotic ribosomes have 80S ribosomes (4×10^6 Daltons) with small subunit 40S and large subunit 60S.
    • Ribosomes have two subunits: small and large.

    Protein Synthesis (Translation)

    • Translation is the process of converting mRNA into an amino acid chain.
    • DNA stores the information for proteins in its nucleotide sequence.
    • There are three steps to translation: initiation, elongation, and termination.

    Initiation

    • The small subunit of the ribosome attaches to the 5' end of the mRNA strand.
    • The small subunit reads the mRNA nucleotides in groups of three (codons) until it runs into the start codon (AUG).
    • The ribosome recruits the large ribosomal subunit and the transfer RNA (tRNA).
    • Key ingredients for translation to start: ribosome, mRNA with codon, and tRNA carrying the first amino acid (methionine).

    Elongation

    • The complete ribosome travels along the mRNA strand and reads the nucleotides in groups of three (codons).
    • The ribosome grabs tRNAs from the surrounding areas and matches their anticodons to the respective codons.
    • Amino acids are joined together by peptide bonds, and the tRNAs leave.
    • Elongation always goes from the 5' end of the mRNA molecule towards the 3' end.

    Termination

    • The third step of translation is when the ribosome runs into a stop codon (UAA, UAG, or UGA).
    • The ribosome places the last amino acid and severs the protein.
    • The ribosome breaks off from the mRNA strand.
    • There are three places on the ribosome where tRNAs bind: A, P, and E site.

    tRNA Binding

    • tRNAs bind to mRNAs inside the ribosome.
    • As tRNAs enter slots in the ribosome and bind to codons, their amino acids are linked to the growing polypeptide chain in a chemical reaction.
    • The end result is a polypeptide whose amino acid sequence mirrors the sequence of codons in the mRNA.

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    Description

    Learn about tRNA (Transfer RNA) and its role in protein synthesis. Understand its structure, functions, and importance in linking amino acids to specific codons in mRNA.

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