week 6

Question 1

what are the two steps in ensuring fidelity to the genetic code

Answer 1

1. aminoacyl-tRNA synthetases (there arer 20: one for each aa)
2. base pairing

Question 2

how does aminoacyl tRNA synthetase correct errors

Answer 2

hydrolytic editing

Question 3

what are the ways that a specific tRNA is recognized by its synthetase

Answer 3

indentifying the tRNA anticodon nucleotides, recognizing the nucleotide sequence of the acceptor stem/arm, reading nucleotide sequences at additional positions on the tRNA

Question 4

Why is peptide synthesis energetically favourable

Answer 4

there is energy stored in the covalent bond b/w aa and tRNA in P site

Question 5

what catalyst is used during translation

Answer 5

peptidyl transferase

Question 6

What kind of cell is EF-Tu found in?

Answer 6

prokaryotes

Question 7

what is the equivalent of EF-Tu and what cell is it found in?

Answer 7

EF1 in eukaryotes

Question 8

what does EF-Tu do?

Answer 8

checks aminoacyl tRNA

Question 9

as it defuses into A site, if bp is not correct, what happens?

Answer 9

EF-Tu is not released and the peptide bond can’t form

Question 10

What happens if bp is correct?

Answer 10

GTP is hydrolyzed and EF-Tu is released

Question 11

incorrectly base paired tRNAs ______________

Answer 11

preferentially dissociate

Question 12

EF-G is found in what type of cell? What is its equivalent?

Answer 12

prokaryotes, EF2 in eukaryotes

Question 13

what is the role of EF-G

Answer 13

helps the ribosome to move the mRNA forward one codon and helps speed up elongation of the pp chain, makes rearrangement of large and small ribosomal subunits more efficient

Question 14

what does polycistronic mean

Answer 14

mRNA that codes for more than one protein (bacteria)

Question 15

what type of cell has Shine-Dalgarno Sequences

Answer 15

prokaryotes

Question 16

do shine-dalgarno sequences get spliced out?

Answer 16

no

Question 17

four steps to initiation of translation in prokaryotes

Answer 17

1. shine-Dalgarno sequences on mRNA bp with rRNA in small ribosomal subunits
2. positioning of small ribosomal subunits to initiating AUG codons on mRNA also requires IFs
3. fMethionine aminoacyl tRNA binds to initiator codon
4. Large ribosomal subunit binds

Question 18

is the human translation release factor a protein or tRNA

Answer 18

protein

Question 19

what are some examples of molecular chaperones?

Answer 19

Hsp60, Hsp70

Question 20

what are some examples of post-translational modifications

Answer 20

phosphorylation and glycosylation

Question 21

why are post-translational modifications necessary

Answer 21

make a protein active, recruit protein to correct membrane or organelle

Question 22

what is ubiquitin

Answer 22

a small protein covalently attached to other proteins

Question 23

what does ubiquitin do

Answer 23

directs proteins to proteasome where they are degraded by proteases