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BSCI330 SPRING > exam 2 the central dogma: translation > Flashcards

exam 2 the central dogma: translation Flashcards

1
Q

how does genetic information stored in chromosomes become useful

A

by being read and converted into proteins in the cytosol

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2
Q

where are mRNA molecules exported to and from

A

exported from nucleus to the cytosol

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3
Q

where do mRNA molecules get translated into proteins

A

cytosol, where they get translated into proteins by ribosomes

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4
Q

how many different combinations does the triple nucleic code allow for

A

4 x 4 x 4 = 64 - enough for the 20 amino acids

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5
Q

what is a codon

A

set of three nucleotides

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6
Q

how many codons does each amino acid usually have

A

more than one

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7
Q

what is the start codon

A

Met - AUG

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8
Q

what does degenerate mean

A

there are multiple codons that encode the same amino acid - no one-to-one correspondence

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9
Q

what is the result of the degenerate nature of the genetic code

A

for a given protein sequence there may be more than one RNA sequence

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10
Q

what happens with a degenerate code and the given RNA sequence

A

cannot determine 100% what the RNA sequence is from the protein sequence

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11
Q

why are intermediary required

A

amino acids cannot directly interact with mRNA

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12
Q

what does tRNA do

A

transfer RNA matches amino acids with codons

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13
Q

what are tRNAs

A

short RNAs with distinctive 3D structure

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14
Q

where does an amino acid get attached to a tRNA

A

covalently attached to 3’ end of tRNA

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15
Q

what is an anticodon

A

complementary to the appropriate amino acid’s codon

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16
Q

what are is the anticodon for CAG

A

CUG

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17
Q

what is the anticodon for AAA

A

UUU

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18
Q

is there an anticodon loop for every RNA

A

yes

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19
Q

what couples an amino acid to tRNA

A

aminoacyl-tRNA synthetase - each amino acid has a distinct one

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20
Q

what is an amino acid first activated by

A

conjunction to AMP

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21
Q

how is conjunction to AMP made

A

by taking ATP and chopping off phosphates

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22
Q

after being activated, what happens to amino acid

A

amino acid is transferred from AMP to tRNA

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23
Q

what does the resulting conjugate have for the amino acid transferred from AMP to tRNA

A

has a high-energy bond between amino acid and tRNA

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24
Q

what happens once the amino acid transfer to tRNA is complete

A

the synthetase proofreads for accuracy

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25
Q

what direction does protein synthesis occur in

A

N-terminal to C-terminal direction (amino acid is added to C-terminal end of growing chain)

26
Q

where is the peptide chain attached during protein synthesis

A

to the last tRNA that was added

27
Q

how is the peptide chain extended by one residue

A

new aminoacyl tRNA replaces old tRNA

28
Q

what is RNA message decoded by

A

ribosomes

29
Q

what do rRNAs make up

A

structural and catalytic core

30
Q

what makes up the structural and catalytic core

A

ribozyme

31
Q

what is the ribozyme

A

enzyme where catalytic component is RNA, not protein

32
Q

what are the two units of the ribozyme

A

large and small

33
Q

which direction does ribosome read mRNA

A

5’->3’, reading 3 bases (one codon) at a time

34
Q

why can proteins translate while transcribing

A

because mRNA reads 5’->3’

35
Q

how many reading frames does each mRNA have

A

3 - ribosomes must choose one and remain consistent or garbled translation occurs

36
Q

what does AUG (Met) use

A

a special initiator tRNA - different than the Met tRNA used for the rest of translation

37
Q

what is translation elongation facilitated by

A

elongation factors

38
Q

what are the elongation factors in prokaryotes

A

Ef-Tu/Ef-G

39
Q

what are the elongation factors in eukaryotes

A

EF1/EF2

40
Q

what does GTPase activity allow for

A

they’re used by elongation factors to allow proofreading and to speed up ribosome translocation

41
Q

what do elongation factors do

A

convert GTP to GDP through hydrolysis, which uses it to regulate the process and proofread

42
Q

what does hydrolysis do

A

puts energy back in the system because forming a peptide bond is energetically expensive

43
Q

what is GTP hydrolysis in cells usually for

A

regulating things

44
Q

when does translation termination occur

A

when the ribosomes encounters a stop codon

45
Q

what happens with translation termination

A

a release factor binds to the ribosomes, causing the hydrolysis of the peptidyl tRNA, releasing the completed protein

46
Q

what happens to the ribosome during translation termination

A

it dissociates into separate small and large subunits, releasing the mRNA, release factor, and remaining tRNA

47
Q

does an in-frame stop codon always lead to termination of translation

A

no - there are circumstances where a stop codon is translated to insert an amino acid

48
Q

what does protein translation occur on

A

polyribosomes

49
Q

how many peptide chains can a ribosome synthesize at a time

A

one, but a cell may need many copies of a protein for every cell of the relevant mRNA

50
Q

when does a next ribosome bind to a cap

A

once the first ribosome has moved far enough along

51
Q

what is a polyribosome

A

a single mRNA may have several ribosomes translating simultaneously

52
Q

what interacts with each other to recognize intact mRNA

A

5’ cap and 3’ tail interact with each other

53
Q

what types of cells do antibiotics affect

A

prokaryotes

54
Q

what are mitochondrial ribosomes like

A

prokaryotic ribosomes more than eukaryotic ribosomes

55
Q

what can prokaryotic ribosomes do

A

cross mitochondrial membrane and effect mitochondrial protein synthesis

56
Q

how are RNA and protein synthesis energetically costly

A

adding each subunit requires the conversion of an NTP into an NMP, the equivalent of hydrolyzing 2 ATPs to ADP

57
Q

what does elongation steps consume

A

multiple ATP/GTP molecules

58
Q

what are elongation steps

A

movement of ribosomes and proofreading

59
Q

what is the info content at the protein sequence level

A

info for 3D structure, cellular location, and protein functions

60
Q

what is the info content at mRNA level

A

same info as protein in code, plus info about initiating and terminating translation and sometimes mRNA stability

61
Q

what is the info content at the DNA level

A

same info as in mRNA, plus info about initiating/terminating transcription, splicing, and anything useful in the introns themselves

BSCI330 SPRING (24 decks)

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