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9 Cards in this Set
- Front
- Back
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Describe the ribosome.
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2 subunits made of rRNA molecules and proteins.
Euk: 80 S; 60 + 40 rRNA functions: catalytic, H bonds to mRNA protein function: promote binding of molecules |
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Describe the tRNA.
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Made from a larger piece of precursor DNA that is cleaved. Usually modified to contain unusual bases
Has a cloverleaf structure |
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Describe charging/aminoacylation.
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How amino acids are added to tRNAs.
1. Amino acid binds to enzyme and is coverted into active form through ATP hydrolysis -> becomes aminoacyladenic acid 2. AA transferred to 3' adenine end of tRNA |
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What are the 3 steps of Translation?
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Initiation
Elongation Termination |
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Describe Initiation.
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Needs IFs to enhance binding proteins. IFs (1-3) bind to small su which can then bind to mRNA.
Shine-Delgarno sequence: base pairs with rRNA of small ribosomal su to make sure the start codon is in the correct position and aligns it correctly: Facilitates initiation. Initiator tRNA carrying f-met binds to P site: IF-3 is released, large su binds to small su, GTP hydrolyzed, IF-1 and 2 are released. EF-Tu binds to tRNA allowing entry to the A site, anticodon bonds with mRNA codon, forming initiation complex. |
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Describe elongation.
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3 sites: E, P (peptido, polypeptide is made), A (aminoacyl tRNA binds first)
The bond between aa and tRNA in P site is broken. At the same time ribosome catalyzes bond formation between f-met and 2nd aa (Now peptide attached to tRNA in A site) Uncharged tRNA from P moves to E, then leaves ribosome complex. Entire complex shifts from A to P site. Large subunite has a tunnel that allows the growing peptide chain to come out. |
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How is Ef-Tu restored?
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wgaf
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Describe termination.
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Termination codon signals action of GTP-dependent factors to cleave peptide from last tRNA.
tRNA released, ribosome units disassemble. |
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Differences in euk. translation.
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More complex. Initiation differs cuz mRNA has poly A tail and 5' cap. Only happens in cytoplasm. Small su scans mRNA till finds start codon in Kozak sequence, which allows binding.
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