2.5.2

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  1. In bacteria, transcription and translation can occur...
    simultaneously
  2. In bacterial cells, do bacterial ribosomes wait for the RNA polymerase to finish transcribing to start translating mRNA?
    No, they often begin translating mRNA while the RNA polymerase is still transcribing.
  3. Are translation and transcription concurrent in Eukaryotic cells?
    no, they are separated by time and space
  4. What do tRNAs do?
    act as adaptor molecules between amino acids and mRNA

    ***Transfer RNA
  5. Who proposed the idea that tRNA acts as an adaptor molecule ?
    Francis Crick
  6. What did Francis Crick propose?
    an adaptor molecule holds amino acids in place while interacting dierectly and specifically with a codon in mRNA
  7. How many nucleotides make up tRNAs in length?
    75-85 nucleotides
  8. What is the secondary structure of of tRNA look like?
    clover leaf
  9. What did researchers noted about their experiment of having radioactive labeled lysine?
    lysines binded to small RNA molecules (tRNAs)
  10. What allows the tRNAs to hold its shape?
    hydrogen bonds between sets of nucleotides
  11. How many different tRNAs are present in a cell?
    20 because there are 20 amino acids
  12. (how amino acids are loaded onto tRNAs) 1.) What binds ATP and amino acid together?
    an active site on aminoacyl tRNA synthetase (enzyme)
  13. (how amino acids are loaded onto tRNAs) Are aminoacyl tRNA synthetase specific to one amino aicd?
    yes
  14. (how amino acids are loaded onto tRNAs) 2.) What happens After the aminoacyl tRNA synthetase binds ATP and amino acid? (3)
    -2 phosphate groups are released

    • -reaction leaves AMP(1 phosphate group) and amino acid bound to the enzyme
    • ***amino acid is "activated" and as high potential energy
  15. (how amino acids are loaded onto tRNAs) 3rd step? (2)
    • -activated amino acid is transferred from tRNA synthetase to the tRNA specific to that amino acid
    • ***when this happens, AMP leaves
  16. (how amino acids are loaded onto tRNAs) 4th step (2)
    -the tRNA synthetase and AMP leave

    -Aminoacyl tRNA is ready to participate in translation
  17. When the tRNA has an amino acid attached to it, what is it called?
    aminoacyl tRNA
  18. How many types of tRNA synthetases are in a cell?
    20 different types
  19. The anticodon portion of the tRNA...
    associates with the complementary bases pairs on mRNA
  20. (initiating translation) What is the Shine-Dalgarno region?
    • portion of mRNA that initially binds to small ribosomal subunit (AGGAGGU)
    • ***this part does not get translated into the protein
  21. (initiating translation) What are initiation factors?
    • -help in associating mRNA to small ribosomal subunit
    • *helps mRNA fit nicely
  22. (initiating translation) IN eukaryotes, what do initiation factors bind to?
    the 5' cap on the mRNA
  23. What is a ribosome composed off?
    • nucleotides
    • *they are made by an RNA polymerase II
  24. (initiating translation) 1st step (2)
    • -a ribosome binding site sequence binds to a complementary sequence in the RNA molecule in small subunit of the ribosome
    • **with the help of initiation factors
  25. (initiating translation) 2nd step
    the aminoacyl tRNA binds to mRNA to start codon
  26. (initiating translation) 3rd step (2)
    • -the large subunit of ribosome binds
    • **this marks the beginning of translation
  27. what are 3 compartments of large subunit of ribosome?
    -A compartment

    -P-compartment

    -E- compartment
  28. What does the a-site do?
    -accepts the next tRNA

    • **acceptor area
    • ** Aminoacyl site
  29. (elongation of polypeptides during translation) 1st step
    -another aminoacyl tRNA comes into the A-site, where its anticodon pairs with the mRNA codon
  30. Why is a ribosome called a ribozyme? (2)
    • the acitve site in the ribosome that catalyzes the peptide bond is all RNA
    • ***this is a type of enzymatic actiivty by the the RNA
  31. (elongation translation) 2nd step
    amino acid attached to tRNA in P site forms peptide bond with tRNA in A site
  32. (elongation translation) 3rd step
    -ribosome moves mRNA down.

    -tRNAs move down one spot to the left.

    - A-site is empty because the tRNA attached to polypeptide moved to the P-site
  33. (elongation translation) which direciton is ribosome traveling ?
    it is moving to the right
  34. (elongation translation) which direction is the mRNA moving as the ribosome moves to the right?
    left in a 5' to 3' direction
  35. (elongation translation) 4th step
    new tRNA binds to the a-site binding its anticodon to the base pair in mRNA
  36. (elongation translation) 5th step (2)
    -peptide bond formation

    -the polypeptide that was attached to the t-RNA  is transferred to the aminoacyl tRNA in the A-site
  37. (elongation translation) step 6th (4)
    -ribosome moves the mRNA down

    -the tRNA attached to polypeptide chain moves into P-Site

    • -empty tRNA from P-site moves down to E-site
    • *it is ejected

    -A-site empty again
  38. How many amino acids are assocaited with the tRNA with the stop codon?
    0
  39. Does a tRNA show up when we reach stop codon?
    • no, a protein release factor shows up.
    • **it is not assocaited with any amino acids
  40. (termination of translation) 1st step (2)
    - when translocation opens A-site and exposes a stop codon, a protein release factor fills the A-site

    -release factor catalyzes the hydrolysis of the bond linking the tRNA in the p-site wth the polypetide chain
  41. (termination of translation) 2nd step (3)
    -the hydrolysis reaction frees the polypeptide which is released from the ribosome

    -empty tRNAs are released either along with the polypeptide or when;

    • -the ribosome separates from the mRNA
    • *the two subunits dissociate
  42. (termination of translation) 3rd step (2)
    -two subunits of ribosomes dissociate

    -subunits are ready to attach to the start codon of another message and start translation anew.
  43. Can there by many ribosomes working on an mRNA at once?
    yes there can be many working on the mRNA
  44. Protein growth AND 5 prime to the 3 prime mRNA
    -protein growth grows as they go from 5' to the 3' of mRNA
  45. Are all the ribosomes in the mRNA making the same protein?
    • yes all the same protein because the mRNA is the same code
    • **only way to get a different proteins is if you change the code

Card Set Information

Author:
 efrain12
ID:
 204546
Filename:
 2.5.2
Updated:
2013-03-03 07:07:16
Tags:
bios
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Description:
translation
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