translation Flashcards by Ruwayda Ali

what is the central dogma

transcription and translation

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what is a codon

A series of three adjacent bases in an mRNA molecule codes for a specific amino acid

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what three codes dont specify amino acids

stop codons, UAA, UAG, and UGA

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what is the function of tRNA

molecular “bridges” that connect mRNA codons to the amino acids they encode

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what is wobble pairing

when atypical base pairs—between nucleotides other than A-U and GC—can form at the third position of the codon

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what is the rule of wobble pairing

G anticodon can pair with C or U but not at A or T in the third position

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what is the process of covalently attaching an amino acid to the tRNA

Charging

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what enzyme attaches the appropriate amino acid onto its tRNA

An aminoacyl-tRNA synthetase (aaRS or ARS), also called tRNA-ligase

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what are the slots on ribosomes where tRNAs find their matching codons on mRNA

A (aminoacyl), P (peptidyl), and E (exit) sites

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what is the most common initiator amino acid

methionine

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during initiation of translation in bacteria, what initiation factors bind to the 30S ribosomal subunit

IF1,2,3 with 2 specifically recognizing the initiator tRNA

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what does the ribosomal complex recognize when binding to the 5’ end of the mRNA

5’ cap

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what direction does the complex “walk” along the mRNA

in the 3’ direction

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what happens when IF3 is released from the complex

50S ribosomal subunit associate with the complex

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what does the 50S binding trigger

hydrolysis of GTP bound to IF2

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what happens after hydrolysis of GTP in bacterial translation

IF1 and IF2 are released

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in bacteria, what brings the second tRNA to the A site

EF-Tu which then leaves the ribosome following GTP hydrolysis

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what pulls the mRNA onwards by one codon

EF-G

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what is required in order for translocation to continue in bacteria

active EF-Tu/GTP complex regenerated by EF-Ts

what proteins recognize stop codons during termination

release factors

what does the release factor cause addition of instead of an amino acid

a water molecule

what doe
a) RF1
b) RF2
in prokaryotic cells recognize

a) UAA or UAG

b) UAA or UGA

in eukaryotic cells the release factor recognizes two termination codons. true or false

false, it recognizes all three

what is the function of RF3

doesn’t recognize specific termination codons but act together with the other RFs

what is a polysome

A number of ribosomes can translate a single mRNA simultaneously, forming a polyribosome

what is an advantage of a polyribosome

enable a cell to make many copies of a polypeptide very quickly

what are the five mechanisms of regulation of translation

``` •binding of repressor proteins •repressors binding to regulatory sequences and initiation factor of 3’untranslated region and 5’ cap •mRNA localization •modulation of IF activity •small regulatory RNA (go read page 42 to 52) ```

how many more initiation factors do eukaryotes have then prokaryotes

6 more

what is scanning in eukaryotic cells

40S ribosomal subunit attaches at the 5’ end of the mRNA and moves downstream (i.e. in a 5’ to 3’ direction) until it finds the AUG initiation codon

what is the function of tetracycline

Blocks attachment of the aa-tRNA to the A site in the ribosome

what is the function of erythromycin

Blocks the movement of the ribosome down the mRNA

what is the function of streptomycin

Blocks formation of the initiation complex and causes miscoding

what is the function of rifamycin

Blocks transcription by blocking binding of RNA polymerase

why shouldn't we antibiotics randomly

* prevent resistance | * avoid killing beneficial bacteria

what helps polypeptide chain coil and fold into 3D shape

chaperon proteins

what are the three ways of protein processing

* Protein Cleavage * Glycosylation * Attachment of Lipids

what does protein cleavage include

Removal of the initiator methionine from the amino terminus

what are the functions of glycoproteins

(1) in protein folding in the ER (2) targeting of proteins for delivery to the appropriate intracellular compartments (3) recognition sites in cell-cell interactions

what are the three general types of lipid additions on proteins

Nmyristoylation, prenylation, palmitoylation

what are the two major protein degradation pathways

* the ubiquitin-proteasome pathway | * lysosomal proteolysis

what is a polypeptide that is highly conserved in all eukaryotes

Ubiquitin

what degrades the polyubiquinated proteins in the UPP

proteasome

what does the lysosomal proteolysis pathway involve formation of

formation of vesicles (autophagosomes) contain proteins derived from the ER

what do the autophagosomes fuse with in the lysosomal proteolysis pathway

Lysosomes

what chaperones are required for lysosomal degradation

A member of the Hsp70 family of molecular chaperones

what proteins are susceptible to degradation the lysosomal proteolysis pathway

long-lived but dispensable proteins (usually during starvation)

what are the amino acids sequence of proteins degraded by lysosomal proteolysis pathway similar to

broad consensus sequence Lys-Phe-Glu-Arg-Gln,