Translation

a. Roles of mRNA, tRNA, and rRNA; RNA Base-pairing Specificity
  • Messenger RNA (mRNA), genes that encode proteins.
  • Ribosomal RNA (rRNA), form the core of ribosomes.
  • Transfer RNA (tRNA), adaptors that link amino acids to mRNA during translation.
  • Small regulatory RNA, also called non-coding RNA.
b. Role and Structure of Ribosome 
Ribosome is cell organell that consist of 65% RNA – ribosome (RNA-r) and 35% protein ribosome or ribonukleoprotein (RNP) that stick or not on the external surface from RE membrane. Ribosome consist of two sub unit, there are large sub-unit and small sub-unit.
Anatomy of ribosome
  • P hole is space to tRNA peptidil.
  • A hole is space to amino-asil.
  • E hole is exit space to tRNA that will leave from ribosome.
  • Ribosome participated bind tRNA and mRNA in located new amino acid at tip of carboxyl.
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                    Biology 8th ed by Campbell and Reece


Role of ribosome
  • Play important role in protein synthesis as a catalyst.
  • The small subunit of ribosome binds mRNA and tRNA
  • The large subunits of ribosome play a role in the process of polypeptide bond formation.


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  c.  Mechanism of Translation

        Video Of Translation Process
  • Initiation
Brings together mRNA, a tRNA with the first amino acid, and the two ribosomal subunits.
  1. First, a small ribosomal subunit binds with mRNA and a special initiator tRNA, which carries methionine and attaches to the start codon.
  2. Initiation factors bring in the large subunit such that the initiator tRNA occupies the P site.

  •  Elongation
Consists of a series of three-step cycles as each amino acid is added to the proceeding one, binding of aminoacyl-trna to the a site, peptide bond formation, and  translocation.
  •  Termination
        Occurs when one of the three stop codons reaches the A site.
  1. A release factor (eRF= RF1). RF1 is bound by a complex consisting of releasing factor RF3 with bound GTP. This complex, with the peptidyl transferase, promotes hydrolysis of the bond between the peptide and the tRNA occupying the P site.
  2. This frees the polypeptide and the translation complex disassembles.  

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