L5 Flashcards

1
Q

methionine

A

new proteins always start with it, prokayotes have methylated methioloine (like chloroplasts and mitochondria)

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2
Q

protein backbone

A

nitrogen carbon NCCNCCN

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3
Q

nucleic acid backbone

A

oxygen phosphorus carbon OPOCCCOPOCCC

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4
Q

first time

A
  1. They Fed a lot of Uracil to a polynucleotide phosphatase, making a lot of
    UUU codons
  2. Had 20 E. coli, gave each a different radioactive amino acid
  3. Then Phenylalanine was synthesized by the bacteria
  4. Now they know UUU codes for Phe
  5. The same can be done with AAA and CCC
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5
Q

second time

A
  1. They put A and C together in different ratios and saw what amino acids got
    synthesized
  2. Based on these ratios and the ratios in which the amino acids are made,
    they can theorize the order of nucleotides, and for which one they code
  3. 6 amino acids were found using the A and C method, this means all other
    amino acids need at least one G or U in the codon
  4. G and U together did not work (because it makes a stop codon), but they
    didn’t know that
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6
Q

ribosomes consistency

A

65% rna and 35% protein, together make particle weight of 70S

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7
Q

proteins start with

A

methionine, AUG

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8
Q

methionine in prokayotes

A

and mitochondria and chloroplasts, is always formylated, not in eukaryotes

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9
Q

inosine

A

Deamination of adenosine makes inosine, found in trna anticodon, can base pair with a c and u

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10
Q

uracil

A

can base pair with a and g and I

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11
Q

EF-Tu

A

he ‘chaperone’ for any tRNAs loaded with an
amino acid. EF-Tu ensures that the loaded tRNA is properly bound
to the mRNA and placed in the active site of the ribosome. Then it
hydrolyses its GTP to GDP and the ribosome can couple the growing
chain to the new tRNAAA

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12
Q

prokaryote translation

A

mrna can be used by ribosomes as soon as it exits the rna polymerase, both take place in cytoplasm

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13
Q

eukaryote translation

A

transcription in nucleus, translation in cytoplasm, mrna must be transported out of the nucleus to be translated

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14
Q

first elongation step

A

-The tRNA that carries aa2 fits into the A site of the
ribosome as a complex with EF-TuGTP.
-If tRNAaa2 is bound correctly to ribosome A site
mRNA triplet, EF-Tu will hydrolyse the GTP and let
go of the tRNA.
- EF-TuGDP will later be recycled to the GTP bound
form by its guanosine exchange factor EF-Ts. Then,
as a new EF-TuGTP it can bind a new tRNA loaded
with an amino acid until it releases it in the
ribosome.

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15
Q

second elongation step

A

-the RNA of the ‘large’ ribosomal
subunit catalyses the formation of a
peptide bond between the carboxyl
end of the growing protein bound to
the tRNA in the P (peptidyl) site and
the amino end of the newly bound
tRNAaa in the A (aminoacyl) site.
- The tRNA in the P site is now without
amino acids at its 3’ end.

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16
Q

third elongations step

A
  • If all is in order, the ribosome
    should translocate along the mRNA
    to the next codon. This is done with
    the help of the EF-G GTPase.
  • The ‘empty’ tRNA in the P site exits
    though the E site, the polypeptide
    bound to the tRNA moves from the A
    site to the P site and the next tRNAaa
    can bring the correct aa in the A site.
17
Q

EF - G

A

ribosome translocate, promotes the translation step in bacterial protein syntheis,

18
Q

puromycin

A

forms a peptide-puromycin bond in the a site of ribosomes, the production of short incomplete proteins is toxic to cells

19
Q

chloraphenicol

A

inhibits peptidyl transfer (prokaryotic specific)

20
Q

cycloheximide and neomycin

A

eukaryote specific, inhibit translocation

21
Q

streptomycin

A

prokaryote specific, inhibitis initiation