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20 Cards in this Set
- Front
- Back
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Regulation of protein synthesis |
Highly energy demanding so coordinated Uses 90% of chemical energy of cell Number of copies made corresponds to number of copies needed Proteins are targeted to cellular locations Degradation keeps pace with synthesis |
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Proteins synthesis is complex |
In eukaryotes: Requires >300 bio molecules 70 > ribosomal 20 AA And so on |
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3 early advances in proteins synthesis |
Proteins synthesized at ribosomes AAs activated for synthesis by attachment to tRNA via Aa-tRNA syhthetases TRNA acts as an adapted to translate mRNA into protein |
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Genetic code for proteins consist of triplets of nucleotides |
20 common AAs 4 letter code in groups of 2 is insufficient but a 4 letter code in groups of 3 is sufficient Use overlapping mRNA code |
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tRNA brings AA to mRNA |
Adaptor |
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Overlapping v no overlapping |
Non: do not share nucleotides Provides much more flexibility and is used in all living systems |
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Genetic code features |
Written in 5’-3’ direction First codon establishes reading frame 61/64 codons code for AAs There are 3 termination codes: UAA, UGA, UAG AIG is start code and Met |
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Most AAs have more than one code |
20 AAs with 61 possible codons Only Met and Trp have a single codon Some codons are less subject to causes mutation |
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Some exceptions with code |
Mitochondria encode their own DNA and use a slightly different code |
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Wobble |
Weak H bonds formed Contain inosinate |
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Molecular recognition |
The codon sequence is complementary with the anticodon sequence Codon base pies with anticodon in MRNA via h bonds The alignment of 2 RNA segments is antiparallel |
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Resistant to mutations |
Degenerates (have same meaning) allows certain mutations to still code for the same AA Silent mutations-different nucleotide but same AA in protein Mutation in first base produces a conservative substitution (a change in AA) GUU-Val but AUU-leu |
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Some mRNAs are edited before protein synthesis |
Alteration, addition, deletion of nucleotides Editing uses guide RNAs (gRNA) that hybridize with mRNAabd act as a template for editing |
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5 stages of protein synthesis |
1. Activation of AAs: AA is attached to tRNA 2. Initiation: mRNA and tRNA bind to small ribosomal subunit, then large unit binds 3. Elongation: cycles of peptide binding occur until stop codon 4. Termination: translation stops when stop codon is reached. MRNA and protein detach and ribosome is recycled 5. Protein folding: posttranslational processing |
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Ribosome |
Make up 25 % of weight in bacteria 65% rRNA (forms core and does peptide bond formation) 35% protein Made of 2 subunits |
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Ribosome bacteria v eukaryotic |
Similar in 2 subunits with mRNA in between them Euk: larger, more complex contain >80 proteins Chloroplasts and mitochondria have simpler ribos than bacteria |
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Characteristics of tRNAs |
Amino acid arm Anticodon arm D arm (contributes to folding) T psi c arm (binding btw base and ribose, helps in folding) |
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tRNA synthetases |
Specific for both AA and tRNA (second genetic code) Specific tRNA molecule for a specific synthetase Anticodon region |
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During intiation. Stage |
First is unique. AUG (met) Initiation factors bind to ribosome then met joins complex EPA: exit, peptide, accept AA |
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During elongation |
Binding to amino site GTP hydrolysis |
