L5

Question 1

methionine

Answer 1

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

Question 2

protein backbone

Answer 2

nitrogen carbon NCCNCCN

Question 3

nucleic acid backbone

Answer 3

oxygen phosphorus carbon OPOCCCOPOCCC

Question 4

first time

Answer 4

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

Question 5

second time

Answer 5

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

Question 6

ribosomes consistency

Answer 6

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

Question 7

proteins start with

Answer 7

methionine, AUG

Question 8

methionine in prokayotes

Answer 8

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

Question 9

inosine

Answer 9

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

Question 10

uracil

Answer 10

can base pair with a and g and I

Question 11

EF-Tu

Answer 11

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

Question 12

prokaryote translation

Answer 12

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

Question 13

eukaryote translation

Answer 13

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

Question 14

first elongation step

Answer 14

-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.

Question 15

second elongation step

Answer 15

-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.

Question 16

third elongations step

Answer 16

• 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.

Question 17

EF - G

Answer 17

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

Question 18

puromycin

Answer 18

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

Question 19

chloraphenicol

Answer 19

inhibits peptidyl transfer (prokaryotic specific)

Question 20

cycloheximide and neomycin

Answer 20

eukaryote specific, inhibit translocation

Question 21

streptomycin

Answer 21

prokaryote specific, inhibitis initiation