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Biochem Final > Translation/Protein Synthesis > Flashcards

Translation/Protein Synthesis Flashcards

1
Q

Prokaryotic ribosomes are a ___ multi-protein, multi-RNA complex, consisting of a large ___subunit (___ proteins + ___ rRNA + ___ rRNA) and a smaller ___ subunit (__ proteins + ___ rRNA).

A
  • 70S
  • 50s
  • 31 proteins, 23S rRNA, 5s rRNA
  • 30s
  • 21 proteins, 16s rRNA
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2
Q

___ constitute most of the bulk of ribosomes and catalyze the formation of ___ ___.

A
  • rRNAs

- peptide bonds

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3
Q

Translation is performed by ribosomes on mRNA and occurs in the ___ to ___ direction. The rate of translation in bacteria is about the same as the rate of ___ (___-___ bases or ___-___ amino acids per second).

A
  • 5’ to 3’
  • transcription
  • 45-50
  • 15-17
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4
Q

In translation, the 5’ end of the coding region corresponds to the ___ ___ of the protein. The 3’ terminus of the coding region corresponds to the ___ ___ of the protein.

A
  • amino end

- carboxyl end

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5
Q

As polypeptides are being synthesized the previously synthesized chain is attached to the ___ ___ of the incoming (new) amino acid and the entire complex is, as a result, attached to the ‘new’ ___. Thus, polypeptides are synthesized in the ___ to ___ terminus.

A
  • free amine
  • tRNA
  • amino to carboxyl
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6
Q

Transcription and translation are coupled together in bacteria, but not in ___. Multiple ___ performing translation on a single mRNA is known as a ___.

A
  • eukaryotes
  • ribosomes
  • polysome
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7
Q

Prokaryotic (but NOT eukaryotic) mRNAs are often ___ - carrying coding for ___ ___ ___ protein.

A
  • polycistronic

- more than one

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8
Q

Translational accuracy is about ___ error per ___to ___ ___ amino acids. Greater accuracy would ___ translation down, so a ___ is struck between the need for accuracy and the need to synthesize proteins reasonably rapidly.

A
  • one
  • thousand to ten thousand
  • slow
  • balance
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9
Q

tRNAs have extensive ___-___ regions. They are typically ___-___ bases long, with ___ regions at least partly in the __ form.

A
  • self-complimentary
  • 73-93
  • duplex
  • A
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10
Q

The shape of tRNAs is that of an ‘’. At the __ end of the tRNA is usually a ‘’ and at the __ end is a ___.

A
  • ‘L’
  • 5’
  • ‘G’
  • 3’
  • CCA
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11
Q

Enzymes that catalyze the linkage of amino acids to tRNA’s __ or __ ends are called ___-___-____ (we nicknamed them “Terry” in class). There are __ of these enzymes - one for each amino acid.

A
  • 3’ or 2’
  • aminoacyl-tRNA-synthetases
  • 20
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12
Q

Amino acids are linked to tRNAs by ___ bonds between the ___ group of the amino acid and either the ___ or ___ ___of the ___ of the terminal ___ residue of the tRNA. The ester bonds are extremely ___ in water and must be protected from it.

A
  • ester
  • carboxyl
  • 2’ or 3’ hydroxyl
  • ribose
  • adenosine
  • unstable
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13
Q

The anticodon loop has ___ bases complementary to the codon in the mRNA. tRNAs provide the ___ function between nucleic acid sequence and ___ ___.

A
  • three
  • translation
  • amino acids
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14
Q

The anticodon loop frequently contains the ___ ___. The base at the ___ end of the codon of the mRNA (corresponds to the base at the 5’ end of the anticodon in the tRNA) is called the ___ ___ because it is ___ ___ for specifying the amino acid to be inserted than the first two bases.

A
  • inosine base
  • 3’
  • wobble base
  • less important
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15
Q

Aminoacyl-tRNA synthetases have the ability to ___ and ___ errors in joining of amino acids to tRNAs. For example, if one puts the wrong amino acid on the end of a tRNA and then adds an appropriate ___-___ ___, the amino acid is readily removed.

A
  • recognize
  • correct
  • aminoacyl-tRNA synthetase
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16
Q

Two regions of aminoacyl-tRNA synthetases are important for editing - called the ___ site (also called the ___ site) and the ___ site.

A
  • activation
  • acylation
  • editing
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17
Q

There are two classes of amino acid tRNA ___. They differ in the way they bind ___ and in which ___ of the ___ ___ they attach the amino acid to.

A
  • synthetases
  • tRNAs
  • hydroxyl
  • ribose ring
18
Q

Class I enzymes attach the amino acid to the:

Class II enzymes attach the amino acid to the:

A
  • hydroxyl on carbon #2.

- hydroxyl on carbon #3.

19
Q

Base pairings in RNA are slightly different than in DNA. For example, - base pairs are not unstable. In addition, as will be seen later, I can pair with ,, or _.

A
  • G-U

- C, U, or A

20
Q

In the genetic code, there are ___ possible combinations of the bases of the codon. Three of the possibilities (___, ___, and ___) are used as ‘stop’ codons. They tell the ribosomes where to stop making protein. A start codon (___).

A
  • 64
  • UAA, UGA, UAG
  • AUG
21
Q

Ribosomes have three sites for binding/holding/releasing tRNAs. They are called the ,, and _ sites, corresonding to the order in which tRNAs move through them (except for the ___ ___ one).

A
  • A, P, E

- very first

22
Q

The ___-___ sequence (___) is located near the ___ start codon in prokaryotic sequences. It is complementary to a sequence in the ___ rRNA and serves to help align the ribosome with the ___ site for translation in prokaryotes.

A
  • Shine-Delgarno
  • GGAGG
  • AUG
  • 16S
  • start
23
Q

In prokaryotes, the first amino acid incorporated into a protein is a ___ form of methionine called ___. The formyl group is put onto methionine ___ it is in the tRNA by a ___ enzyme

A
  • formylated
  • fMet
  • after
  • transformylase
24
Q

Formylation of methionine in prokaryotes ___ the otherwise free amino end from ___ intramolecularly and ___ transcription.

A
  • protects
  • reacting
  • terminating
25
Q

Peptides exit the ribosome as they are being synthesized via a ___ in the structure.

A

-tunnel

26
Q

Initiation of protein synthesis starts with binding of ___ and ___ to the ___ ribosomal unit. The mRNA is aligned with the ___ ___ site.

A
  • IF1
  • IF3
  • 30s
  • Shine-Delgarno
27
Q

IF2 (when bound to GTP) acts to carry the ___-___ to the ___ ___ of the 30S subunit and base pairs it with the ___ ___ codon.The complex of mRNA, IF1, IF2, and Met-tRNAf is called the ___ ___ ___.

A
  • Met-tRNAf
  • P site
  • AUG start
  • 30S initiation complex
28
Q

Hydrolysis of the ___ in ___ results in release of the ___ and ___ from the initiation complex. That, coupled with binding of the ___ subunit yields the 70S initiation complex with Met-tRNAf in the ___ ___ and the A and E sites open.

A
  • GTP
  • IF2
  • IF2 and IF1
  • 50s
  • P-site
29
Q

The process of elongation begins on the ___ ___ ___. ___ (a G protein coupled to GTP) carries a ___ tRNA to the ___ ___ of the complex. If the tRNA anti-codon base pairs properly with the codon in the mRNA, it stays matched with the codon and GTP is ___ on EF-Tu and ___ ___ is released.

A
  • 70s initiation complex
  • EF-Tu
  • charged
  • A site
  • hydrolyzed
  • EF-Tu GDP
30
Q

If the tRNA anti-codon does not form a stable base pairing with the complex, the entire charged ___-___-___ complex ____.

A
  • tRNA-EF-Tu-GTP

- dissociates

31
Q

Next, the ___ group on the tRNA in the ___ ___ is transferred and ___ linked via peptide bond to the amino acid on the tRNA in the ___ ___. This reaction is catalyzed by an enzymatic activity called ___ - a ribozyme activity of the ___ rRNA in the ___ subunit.

A
  • peptide
  • P site
  • covalently
  • A-site
  • peptidyltransferase
  • 23S, 50S
32
Q

The tRNA in the A site along with the peptide it is covalently attached to is transferred to the ___ ___ as the “___” tRNA in the P site is moved to the ___ ___

A
  • P site
  • empty
  • E site
33
Q

EF-G-GTP is involved in the process and ___ is ___ in the process. EF-G-GTP has a similarity to the ___-___-___ complex and may act to displace it.

A
  • GTP
  • hydrolyzed
  • tRNAaminoacid-EF-Tu-GTP
34
Q

As the old tRNA is released from the ___ ___, the empty A site accepts the ___ ___ corresponding to the next codon. The net result of one turn of this cycle is that the polypeptide has grown by ___ ___ ___ residue and the ribosome has moved along the ___ by ___ nucleotide residues. The process is repeated until a ___ signal is reached.

A
  • E- site
  • aminoacyl tRNA
  • one amino acid
  • mRNA
  • three
  • termination
35
Q

The process of translation ___ begins when a stop codon appears in the ___ ___ of the ribosome. Termination of translation requires action of ___ ___ (___, ___)

A
  • termination
  • A-site
  • release factors
  • RF1, RF2
36
Q

RF-1 and RF-2 carry ___ to the ___ ___.The ___ ___ transfers the polypeptide on the tRNA in the ___ ___ to water, thus ___ the completed polypeptide from the ribosome.

A
  • water
  • A site
  • peptidyl transferase
  • P site
  • releasing
37
Q

Translational diffs in eukaryotes relate to the structure of eukaryotic cells. Targeting of proteins to organelles, the membrane, or outside of the cell, starts during ___ ___. Proteins destined to leave the cytoplasm have a ___ ___, consisting of a stretch of ___ amino acids near their ___ terminus.

A
  • protein synthesis
  • signal sequence
  • hydrophobic
  • amino
38
Q

When the ___ sequence emerges from the ribosome during translation, it is recognized by the ___ ___ ___ (___), which takes the entire ___/___/___ complex to the endoplasmic reticulum.

A
  • signal
  • signal recognition particle
  • SRP
  • ribosome/mRNA/polypeptide
39
Q

At the ER it interacts with the ___ ___ and in the process it links the ___ with the emerging polypeptide sequence to the ___.

A
  • SRP receptor
  • ribosome
  • translocon
40
Q

The polypeptide passes through the ___ channel as it is being made and when the signal sequence completely exits the translocon, a ___ ___ clips it free of the rest of the polypeptide. The translation process continues until the ___ ___ is reached and then everything releases from the ___.

A
  • translocon
  • signal peptidase
  • stop codon
  • translocon
41
Q

The polypeptide remains in the ___ ___ where it is further process to travel to the ___ for additional ___ and ___. Other sequences in the polypeptide may help to direct modifications and/or the final ___ of the mature protein.

A
  • Endoplasmic reticulum
  • Golgi
  • processing and targeting
  • destination
42
Q

Antibiotics frequently are designed to target various aspects of translation. They include ___ (interferes with binding of ___ tRNA to ribosome), ___ (inhibits binding of ___-___), ___ (inhibits ___ ___ activity), and ___ (causes premature ___ ___).

A
  • streptomycin (formylmethionyl)
  • tetracytline (aminoacy-tRNAs)
  • chloramphenical (peptidyl-transferase)
  • puromycin (chain termination)

Biochem Final (5 decks)

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