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Molecular Biology > Lecture 8 Translation > Flashcards

Lecture 8 Translation Flashcards

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1
Q

______ is a set of rules that convert the nucleotide sequence of a gene into the amino acid sequence of a protein using mRNA as an intermediate

A

Genetic code

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2
Q

each group of 3 consecutive nucleotides in RNA is called a ____

A

codon

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3
Q

a total of ____ triplet codons code for the 20 known amino acids, thus the code is _____

A

61, degenerate

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4
Q

The _____ hypothesis postulates that the genetic code is read by molecules that recognize a codon and carry the corresponding amino acid

A

adaptor hypothesis

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5
Q

______ serves as an adaptor that binds to a specific codon and brings with it an amino acid for incorporation into the polypeptide chain

A

Transfer RNA or tRNA

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6
Q

_____ secondary structure of tRNA. tRNA folds up into a defined 3-D structure and contains 4 short double-helical segments

A

Cloverleaf

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7
Q

___ regions of unpaired nucleotides are crucial to the functions of tRNA. What are they

A
  1. Anticodon loop (as set of 3 consecutive nucleotides that pair with a a complementary codon in an mRNA molecule) The other is 3’ CCA terminal region (which binds the amino acid that matches the corresponding codon)
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8
Q

is there more than one tRNA for most amino acids

A

yes

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9
Q

some tRNAs require accurate base-pairing only at the first two positions of the codon and can tolerate a mismatch (or ____) at the third position

A

Wobble

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10
Q

The amino acid is activated for protein synthesis by an ________ in two steps

A

aminoacyl-tRNA synthetase enzyme

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11
Q

Recognition and attachment of the correct amino acid to the corresponding tRNA is catalyzed by

A

aminoacyl-tRNA synthetases

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12
Q

aminoacyl-tRNA syntheses covalently couple an amino acid to the

A

3’-terminal ribose residue of its corresponding tRNA to form an aminoacyl-tRNA

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13
Q

do most cells have a different aminoacy-tRNA synthetase enzyme for each amino acid

A

yes

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14
Q

Aminoacyl-tRNA syntheses contain highly discriminating amino acid

A

activation sites

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15
Q

The correct amino acid has the ______ affinity for the active-site pocket of its aminoacyl-tRNA synthetase and is therefore favored over the other 19. Amino acids larger than the correct on ______

A

highest affinity, do not bind to active site

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16
Q

do aminoacyl-tRNA synthetases contain an editing site for proofreading

A

yes

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17
Q

The editing (hydrolytic) site of aminoacyl-tRNA synthetase cleaves ________ species that are _______

A

cleaves activated species that are smaller than the correct one

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18
Q

Hydrolytic editing raises the overall accuracy of tRNA charging to approximately one mistake in ______ couplings

A

40,000

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19
Q

what is the molecular weight of the eukaryotic 80S ribosome

A

4,200,000

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20
Q

what is the molecular weight of the prokaryotic 70S ribosome

A

2,500,000

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21
Q

What is the size of the prokaryotic ribosome

A

70S

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22
Q

What is the size of the eukaryotic ribosome

A

80S

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23
Q

Ribosome is a complex catalytic machine, consisting of two subunits, each contains different ________ and several _____

A

ribosomal proteins and several ribosomal RNAs (rRNAs)

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24
Q

____ and not proteins determine the overall shape of the ribosome, its ability to position tRNA on the mRNA, and its catalytic activity in forming peptide bonds

A

rRNAs

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25
Q

____ provides the framework on which the tRNAs are accurately matched to the codons of the mRNA

A

small subunit of ribosome

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26
Q

____ catalyzes the formation of the peptide bonds that link the amino acids together into a polympetide chain

A

the large subunit of the ribosome

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27
Q

Protein synthesis is performed on the ______, which ensures accuracy and maintains _____

A

ribosome, correct reading frame

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28
Q

When not synthesizing proteins the 2 ribosome subunits are

A

separate

29
Q

mRNA is pulled through the ribosome in a _____ direction

A

5’-3’ direction

30
Q

The 2 ribosomal subunits join together at the __ end of an mRNA and initiate protein synthesis

A

5’

31
Q

As the codons enter the core of the ribosome the mRNA sequence is ______ using ___

A

translated into amino acid sequence using tRNAs

32
Q

The ribosome releases protein when encountered by a ____

A

stop codon

33
Q

The ribosome contains ___ binding sites for RNA. What are they

A
  • 4

- tRNA A (for aminoacyl), P (for peptidyl), and E (for exit) sites and 1 for mRNA

34
Q

The A-,P-, and E-sties on the ribosome are formed by the rRNA of the ____ subunit

A

large

35
Q

The mRNA is bound within the ___ subunit of the ribosome

A

small

36
Q

The tRNA molecules are held in the A and P sites only if

A

their anticodon forms base pairs with complementary codons in mRNA threaded through the ribosome

37
Q

Amino acids are added to ____ terminus of polypeptide

A

C-Terminus

38
Q

The fundamental reaction of protein synthesis is formation of _____ bond between amino acids

A

peptide

39
Q

The peptide bond formation between amino acids occurs between the _____ at the end of the polypeptide and an ____ of the incoming amino acid

A

Carboxyl group, amino group

40
Q

A protein is synthesized stepwise from its _____ to ____ terminal end

A

N-terminal to C-terminal

41
Q

Once protein synthesis has been initiated, each new amino acid is added to the elongation chain in a cycle of reactions containing ____ steps; what are they

A
  • 4
  • tRNA binding
  • peptide bond formation
  • large subunit translocation
  • small subunit translocation
42
Q

all known mRNA molecules contain signals that define the

A

beginning of each encoded polypeptide chain

43
Q

Translation begins with the ____ codon ____, which codes for ____

A

initiation codon AUG, which codes for methionine

44
Q

The 70S subunits are

A

50S and 30S

45
Q

The 80S subunits are

A

60S and 40S

46
Q

in eukaryotes, the initiator tRNA-methionine complex is first loaded into the ____ subunit along with additional proteins called

A

small ribosomal, eukaryotic initiation factors, or eIFs

47
Q

After the initiator tRNA has bound to the small ribosomal subunit, the small ribosomal subunit

A

binds to the 5’ end of mRNA (recognized by its 5’ cap and the bound initiation factors (eIF4E and elF4G)

48
Q

What ins the recognition consensus site ahead of AUG in eukaryotes

A

5’-ACCAUGG-3’

49
Q

after initiation, the factors ____, the large subunit ___

A

drop off, the large subunit joins the small subunit and the protein synthesis starts

50
Q

What are the bound initiation factors that the small ribosomal subunit uses to recognize the 5’ cap

A

eIF4E and eIF4G

51
Q

____ factors makes translation more efficient and accurate

A

Elongation factors

52
Q

Elongation factors care called _____ and ____ in bacteria and ____ and ____ in eukaryotes

A

EF-Tu and EF-G in bacteria and EF1 and EF2 in eukaryotes

53
Q

EF-Tu binds ____ and the _____ and then functions to

A

GTP and the aminoacyl tRNA ad then escorts it to the ribosome (checks whether amino acid-tRNA match is correct) and monitors interaction between anticodon o incoming aminoacyl tRNA and the codon of mRNA

54
Q

Interaction of EF-Tu, tRNA and ribosome introduces critical _____ steps into protein synthesis

A

proof-reading

55
Q

GTP hydrolysis brings about conformation changes in ribosome that

A

increase efficiency greatly

56
Q

What are the stop codons

A

UAA, UAG, UGA

57
Q

The stop codons are recognized by ______, proteins that promote the release of the completed protein from the tRNA

A

Release Factors (RFs)

58
Q

Release factors bind to ____ site of ribosome containing the stop codon and catalyze the addition of a water molecule instead of an amino acid. This reaction frees the ___ group of the polypeptide from ___

A

A site, Carboxyl group of the polypeptide from tRNA

59
Q

many effective antibiotics are compounds made by fungi that inhibit ________

A

bacterial protein synthesis

60
Q

Antibiotics are able to exploit

A

structural and functional differences between bacterial and eukaryotic ribosomes

61
Q

Many antibiotics bind to ______ and interfere with protein synthesis by blocking ribosomal function

A

Ribosomes

62
Q

Specific effect of tetracycline

A

blocks binding of aminoacyl-tRNA to the A site of ribosome

63
Q

Specific effect of streptomycin

A

prevents the transition from translation to chain elongation and also causes miscoding

64
Q

Specific effect of Erythromycin

A

Binds in the exit channel of the ribosome and thereby inhibits elongation of the peptide chain

65
Q

Specific effect of Puromycin

A

Causes the premature release of nascent polypeptide chains by its addition to the growing chain end

66
Q

Specific effect of Cycloheximide

A

Blocks the translocation reaction on ribosomes

67
Q

What antibiotics bind to small ribosomal subunit (30S) of bacterial ribosome

A
  • Tetracycline, Spectinomycin, Hygromycin B, Streptomycin
68
Q

What antibiotics bind to the large ribosomal subunit of the bacterial ribosome

A
  • Chloramphenicol, streptogramin B, and erythromycin

Molecular Biology (14 decks)

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