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25 Cards in this Set
- Front
- Back
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translation |
decoding and mrna into a polypeptide chain by the ribosome followed by modification of the polypeptide into a fxnl protein |
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translation apparatus |
3 components 1. ribosomes 2. trna's 3. mrna's |
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Ribosomes |
large complex cell organelles that serve as sites for translation made up of small subunit=40 s (18s plus ribonuclear proteins) and large subunit=60s (5s + 5.8s + 28s plus ribonuclear proteins) |
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small ribosomal subunit |
40s; from 18s reads the mrna from which a protein is synthesized; monitors complementarities btwn codons and anticodons |
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Large ribosomal subunit |
60s; from 5s, 5.8s, 28s joins the AAs to form polypeptide chain, facilitates the peptide bond formation between AAs has 3 binding sites on it: E, P and A and has rrna and proteins present: ribozymes (ribonucleic acid enzymes) or catalytic rnas are present in the 60s; they catalyze peptide bond formation |
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A site aka Aminoacyl site |
binds to aminoacyl trna or a trna bound to an aa new aa |
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P site aka peptidyl site |
bind to a peptidly trna or a trna containing the growing polypeptide chain peptide bond formation |
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E site or exit site |
binds to free or uncharged trna (trna without an aa) before it leaves the ribosome bind e then fall off |
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trna and structural features |
small single standed cytoplasmic rna with a folded 3d structure that serves as an adapter in translating the language of nucleic acids (mrna) into proteins cloverleaf model has amino acid arm |
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prokaryotic and eukaryotic aa's are coded for by the same codons |
this is universality of the genetic code |
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degeneracy of the genetic code |
the number of codons exceeds the number of amino acids present in a cell. there are only 20 amino acids in the cell and 4 to the 4=64 possible codon combos. each AA can be coded for by more than one codon (multiple codons) in a cell. this is what makes the genetic code degenerate like 3 different codons can give me leucine |
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wobble hypothesis |
each trna has to be able to recognize and bind to more than one codon that codes for its particular aa it has attached to it. the first two bases (5' end) on the mrna are strong bp'd to their complement on the 3' end of anticodon on the trna the 3rd and last base (3 end) on mrna wobbles, pairs loose and nonspecific to the last base (5 end) on anticodon. this enables trna to bind on multiple codons differing in the 3rd base multiple codons coding for a particular aa differ in the 3rd base of their codon. A is never found in 5' anticodon position C binds normall I, U and G are the wobble bases (on the trna) the presence of any of these bases at the 5' end (end) of an anticodon of trna enables the trna to bind multiple mrna codons differing in their 3rd base |
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I at 5' end of anticodon (trna) |
can bind AUC |
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U at 5' end of anticodon (trna) |
can bind A, G |
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G at 5' end of anticodon (trna) |
can bind C or U |
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the 5' end of trna |
contains poly guanylate (pG) residues |
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D arm of trna |
contains 2-3 residues of an unusual base dihydrouridine d is the side loop close to 5' end |
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TuC |
contains riothymidine and pseudouridine (modified bases) its the side loop on 3' side |
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D and TuC |
these arms (the side loops) enable folding of the trna mlcl and are used for orientation of the trna in aminoacyl trna synthetases |
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mrna's role in translation |
mrna provides the genetic code that is decoded into AA sequence of specific proteins by translation has 5' methyl cap and 3' poly tail cap helps mrna bind to small subunit of ribosome |
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start codon |
AUG coding for methionine |
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stop codons |
UAA, UAG, UGA |
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Reading mrna during translation is in what direction |
5' to 3' |
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first step of translation |
activate AA's occurs when they get attached to their specific trnas in the cytosol. enzme aminoacyl trna synthetase leads this process formation of ester linkage btwn cooh OF aa AND OH group on adenine residue of the CCA sequence, A is last one on 3' this rxn occurs in 2 steps and requires 2 ATPS. one used directly and one used to regenerate ADP from the AMP produced. AA + tRNA + 2ATP --> Aminoacyl-trna +AMP+2Pi |
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aminoacyl trna synthetase |
2 fnxs: it activates AA by attaching it to its specific tRNA and this prepares it for incorporation into a protein it has proofreading fxn which ensures attachment of correct AA to its specific trna and thus placement of the correct AA at the specific position of a growing polypeptide chain |
