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Protein Synthesis

Ch. 30

QuestionAnswer
What does TRANSLATION employ? Translation employs the GENETIC CODE.
2 Amino Acids encoded by unique codons Methionine and Tryptophan
tRNA's bridge what? the two languages. Nucleic Acids to Amino Acids.
5'-UUU-3' Codon Encodes Phenylalanine
5'-AUG-3' Codon on mRNA specifies methionine
3 Different Translation-Termination Signals/Codons 5'-UAA-3' 5'-UAG-3' 5'-UGA-3'
Translation initiation signal/codon 5'-AUG-3' (that also, codes for methionine).
5'-UGG-3' Codon specifies Tryptophan
The 3rd position of the Codon binds to what part of the Anticodon? 1st position of the anticodon.
What protein (enzyme) is the true bilingual speaker? Aminoacyl tRNA synthetases.
The ribosome is the site of translation, discovered in what type of experiment conditions? The ribosome is the site of translation, discovered in in vitro protein synthesis.
What is the least number of tRNAs needed? 31 tRNAs
Wobble is specific to what? Wobble is specific to ONLY the third position (the 3'-most position) of the Codon (which is the same as saying the 1st position of an anticodon).
What are Shine-Delgarno Sequences? They are Cis-elements of Translation initiation in PROKARYOTES only.
What end (5' or 3') on mRNA is the Guanosine CAP located? 5'. Which is the right-most end, or most upstream.
What are the Cis-elements in Eukaryotic Translation Initiation? The 5-'AUG-3' Codon.
What are the Trans-elements in Eukaryotic Translation Initiation? Small Ribosomal Subunit. Initiating tRNA. Initiating Factors.
How many tRNA binding sites are on the Eukaryotic ribosome (as a whole)? 3. The E,P, and A sites.
Of which Eukaryotic Ribosomal subunit does the E,P, and A, tRNA binding sites belong to? The E,P, and A sites are a product of the coming together of both the small and large ribosomal subunits.
To which Eukaryotic Ribosomal subunit does the enzymatic activity, Peptidyl Transferase, belong to? The Large Ribosomal Subunit.
What does Peptidyl Transferase do? makes the peptide bonds that join amino acids to make a polypeptide. In Eukaryotes
Where is the Pt Site located? Only on the large ribosomal subunit of Eukaryotes.
Where is mRNA draped acrross in Translation Elongation? mRNA is draped acrross the Small Ribosomal Subunit it Translation Elongation.
What do the E,P,and A sites include? What do they consist of? the tRNA binding sites, and, the mRNA binding sites.
How are the tRNA binding sites and mRNA binding sites (E,P, and A) created? By the two ribosomal subunits coming TOGETHER.
Where is the Pt and Polypeptide exit channel located? Only on the Large ribosomal subunit
When is the only time have an aminoacyl tRNA in the P-site? Translation Initiation
Usually we have what located at the Ribosomal P-site? Peptidyl-tRNA. A tRNA that has an ester-linkage to a peptide - a polypeptide chain that is growing.
When does the initiation complex form? The end of Translation initiation.
The Initiation Complex of Translation Initiation has what bound to its P-site? Initiating tRNA.
What is the name for the aminoacyl tRNA that is present the only time have an aminoacyl tRNA in the P-site? Initiating tRNA.
What does the A-site of the ribosome do? The A-site, Aminoacyl-site, allows the binding of an aminoacyl tRNA.
EF-tu has what kind of protein-activity? GTP-ase. It is a fidelity timer.
EF-tu has homology to what? EF-tu has homology to the small G-proteins like Ras, and heterotrimeric G-proteins. And just like those, it uses its GTP-ase activity as a timer.
EF-tu is what kind of acting factor? EF-tu is a Translation trans-acting factor.
Amino-acyl tRNA's that are NOT bound to EF-Tu's, do not stay where? The A-site.
If Amino-acyl tRNA-s, bound to EF-Tu, stay in the A-site long enough, what can, and should happen? EF-Tu hydrolyzes GTP, causing the Amino-acyl tRNAs to
How are activated amino acids (aminoacyl-tRNAs) made? The Carboxyl group of an amino-acid is bound to the 3'-end of a tRNA molecule.
The linking of an amino acid to its correspding tRNA is catalyzed by what enzyme? Aminoacyl tRNA Synthetase.
What is the energy source for Aminoacyl tRNA Synthetase activity? ATP cleavage.
tRNA serves as the adaptor moecule that binds to what? A specific codon and brings with it an amino acid for incorporation into the polypeptide chain.
What end of tRNA does Amino Acids bind to? The 3'-OH group of the adenosine residue at the 3' terminus of the tRNA molecule.
What 5' end of tRNA is made up of what? The 5'-end of tRNA is phosphorylated pG.
All tRNA molecules are usually how long? A single chain of 73-93 ribonucleotides.
All tRNA molecules contain many unusual what? All tRNA molecules contain many unusual bases. Some are methylated or dimethylated derivatives of A, U,C and G.
The unusual bases of tRNA, like methylated bases, have what repercussions? Some prevent formation of correct base pairings, some create hydrophobic-ness that prevents correct binding to other proteins.
The 3'-CCA terminal region of tRNA is called what? The acceptor stem.
What is the code for the tRNA acceptor stem. 3'-CCA terminal region.
What is the DHU loop of tRNA made of? Dihydro Uracil residues.
What is the L-shaped structure? 3D tRNA. The anticodon loop is the top of a capital L. The 3'-CCA is the end/bottom of an L.
Where is the anticodon located in tRNA? In a loop near the center of the sequence.
The activated Amino Acid and the Anticodon are located at what position of tRNA L-shape? The activated Amino Acid and the Anticodon are located at opposite ends of the L-shape.
What bond connects the tRNA 3'CCA terminus to an Activated Amino Acid? Amino acids bind the 3'CCA end of tRNA by either connecting to tRNA'S 2'- or 3'-OH of the 3'-adenosine residue.
Why is amino acid binding to tRNA crucial? amino-acid = tRNA binding established the genetic code. Codon/Anticodon binding dictates the AA position in a polypeptide chain. Second, a peptide bond between free-amino acids is not thermodynamically favorable. The amino acid must fist be "activated".
Amino acids become activated, or charged, by what process? AA are activated by Adenylation. Catalyzed by activating enzymes called aminoacyl-tRNA synthetases.
What is the first step in the formation of activated AA? Formation of an aminoacyl adenylate, from an AA and ATP.
What are the substrates for aminoacyl-tRNA synthetases? AA, ATP.
What are the names of Activated Amino Acids? Aminoacyl-AMP. Aminoacyl adenylate.
Once an Amino Acid is activated, or charged, how does it attach to tRNA? The Aminoacyl group of Aminoacyl Adenylate, aka, Aminoacyl-AMP, is transfered to tRNA, to form aminoacyl-tRNA.
The equivalence of two molecules of what energy source is consumed in the synthesis of EACH aminoacyl-tRNA? The equivalence of 2 molecules of ATP. One of them is consumed in forming the ester linkage of Aminoacyl-tRNA, and the other is consumed in driving the rxn forward.
Explain the rxn that makes aminoacyl adenylate The carboxylate group of the correctly positioned AA attacks the alpha phosphoryl group of ATP.
The Aminoacylated 3'CCA of Aminoacyl-tRNA Synthetase can swing where? The Aminoacylated 3'CCA of Aminoacyl-tRNA Synthetase can swing OUT of the activation site, and into the editing site.
Aminoacyl-tRNA can be edited without what? Dissociating from the synthetase.
Class I aminoacyl tRNA synthetases bind where on tRNA? They acylate the 2'-OH of the 3'CCA terminus Adenosine of the tRNA.
Class II aminoacyl tRNA synthetases bind where on tRNA? They acylate the 3'-OH of the 3'CCA terminus Adenosine of the tRNA.
rRNAS are folded into what? folded into defined structures with many short duplex regions.
Protein Synthesis goes in what direction? Protein Synthesis begins at the amino terminus and extends toward the carboxyl terminus.
In what direction is mRNA translated? mRNA is translated in the 5'-3' direction. The same as Transcription.
In Prokaryotic Transcription, what end of mRNA transcript interacts with the ribosome to start translation? The 5' end of the new mRNA transcript.
Explain the Polysome. Many ribosomes can be translating an mRNA molecule at the same time. The group of ribosomes bound to an mRNA molecule is a polyribosome, or, polysome.
The first translated codon is nearly always located where? more than 25 nucleotides away from the 5' end.
mRNA molecules in prokaryotes are _____ Polycistronic. Encode two or more polypeptide chains.
The purine Rich region, located on the 5' side of the initiator codon, in Prokaryotes is what? Shine-Dalgarno sequence.
Each initiator region of prokaryote mRNA contain what? 5'-AUG-3' codon. A purine-rich sequence on the 5'side of that codon (Shine-Dalgarno Sequence).
What is complementary to the Shine-Dalgarno sequence? 3'end of the rRNA component of the small subunit.
What 2 reaction determine where protein synthesis starts? 1. the pairing of mRNA bases with the 3'end of 16S rRNA (on the ribosome). 2. Pairing the initiator codon on mRNA with the anticodon of the initiator tRNA molecule (aka the aminoacylated tRNA).
Proteins synthesis in BACTERIA (prokaryotes) stars with what? N-formylmethionine (fMet).
What is the difference between tRNA subM, and tRNA subF? Only tRNA subF is an initiator tRNA in prokaryotes. tRNA sub M inserts Methionine into internal positions (not used to start protein synthesis in Prokaryotes). tRNA subF is the initiator tRNA for bacteria.
What does the "f" in tRNA sub F stand for? Indicates that methionine attached to the initiator tRNA can be formylated.
What can RNA subF bind? All three possible initation codons, but, with decreasing affinity. (AUG>GUG>UGG)
The amino group of aminoacyl-tRNA in the A attacks what? The ester linkage between the initiator tRNA and the formylmethionine molecule.
What is the Pt side made up of? Bases that help form an -NH2 group on the A-site aminoacyl-tRNA
When the peptide bond is formed, the peptide chain is now attached to what? tRNA in the A-site on the small subunit
When the peptide chain is attached to the tRNA in the A-site, what has happened to the tRNA? the tRNA and its peptide that was once in the A-site is now in the P-site of the large subunit. The tRNA in the Psite of the small subunit is now uncharged.
efG is what? Elongation Factor G. A protein enzyme that is driven by the hydrolysis of GTP. On GTP hydrolysis, EF-G undergoes a conformational change that moves the peptidyl-tRNA in the A site to the P site.
What complex decodes the codon-anticodon interactions? The ribosome.
What protein Initiation Factors are essential for Prokaryotic Translation Elongation? IF1, IF2, IF3.
What binds to EF-Tu? Met-tRNA subM
Translation Termination involves what? Translation termination involves stop codons recognized by Release Factors (RF's) , that promote release of the completed protein from the last tRNA.
What kind of cell type has larger Ribosomes? Eukaryotes (60S and 40S).
What is the Initiator AA in Eukaryote Translation? Methionine
What is the Initiator AA in Prokaryotic Translation? N-formylmethionine. fMet.
Aminoacyl-tRNA's called Met-tRNAi or Met-tRNAf, are found in what translation Initiation of what cell types? Prokaryotes.
What shape is Eukaryotic mRNA? Circular.
Where does the initiating tRNA bind to in the ribosome of Prokaryotes? P-site. The P-site is a tRNA-binding site on the 50S Ribosome.
What is the name of the initiating tRNA of Prokaryotes? Met-tRNA subF
What is the name of the initiating tRNA of Eukaryotes? Met-tRNA subi.
How are proteins synthesized? Amino-to-Carboxyl direction.
When amino acids are added to a growing polypeptide chain, where do the attach to? Carboxyl end of the growing peptide chain.
Where does the 3'-CCA terminal of tRNA move? between the Activating site and Editing site of Aminoacyl-tRNA Synthetase.
How is DNA POL similar to aminoacyl-tRNA Synthetase? Editing without dissociation causing high fidelity.
mRNA is translated in what direction? 5'-3'
Unique to prokaryotes, what kind of genes do they have? Polycistronic genes. They encode 2 or more polypeptide chains.
Translation initiation depends upon what 2 rxns? The 3'-end of 16S rRNA on the 30S subunit binding to the Shine Dalgarno sequence. And, the tRNA anticodon binding to the mRNA start codon.
What does the Translation Initiating in Prokaryotes require? Initiating factors (IF1 and IF3), GTP-bound IF2, 30S, initiating tRNA (Met-tRNAf), mRNA start codon, mRNA shine dalgarno sequence.
Created by: abenvie
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