Translation

Question 1

Commaless

Answer 1

codons aren’t separated by noncoding bases.

They are read continually without punctuation, no indication of one codon stopping and another starting

Question 2

Reading Frame

Answer 2

The reading frame starts with a start codon and ends with a stop codon.

Question 3

Modified bases in tRNA

Answer 3

Adenine to inosine (I)
Uridine to pseudouridine (w)
Uridine to dihydro-uridine (D)

Question 4

Use of modified bases

Answer 4

The different base pairs give the tRNA a shape that fits better in the ribosome.

Question 5

tRNA ends

Answer 5

…CCA-3’
amino acid binding site

5’-G…
forms acceptor stem with binding site

Question 6

aminoacyl tRNA synthetase

Answer 6

enzyme that charges tRNA
specificity for amino acid, so 20 of them; services multiple tRNA types

Question 7

aminoacyl tRNA synthetase reactions

Answer 7

Amino acid links with ATP; carboxyl group links to AMP phosphate, forming aminoacyl AMP

Amino acid attaches to tRNA; aminoacyl AMP’s carboxyl end is transferred to A at binding site

Question 8

Isoaccepting

Question 9

Prok. ribosomes & components

Answer 9

70s

50s large
peptidyl transferase / 23s rRNA

30s small
16s rRNA

Question 10

necessary components for protein synthesis initiation

Answer 10

mRNA
50s & 30s
initiation factors (IFs)
tRNAfMet, special initiator tRNA
Guanosine triphosphate (GTP)

Question 11

IF1

Answer 11

In translation initiation, IF1 blocks the A site from being bound by the tRNA

Question 12

IF2

Answer 12

In translation initiation, IF2 is a GTPase that forms a complex with GTP. This recruits a charged tRNA, which it binds to the P site.

Question 13

IF3

Answer 13

In translation initiation, IF3 prevents the 30s from binding prematurely to the 50s

Question 14

Shine-Dalgarno

Answer 14

exists upstream of the start codon in the mRNA.

It is a conserved ribosome binding sequence (RBS).

base pairing with the 16s rRNA in the 30s enables proper positioning of the mRNA

aligns the AUG start codon

Question 15

30s initiation complex

Answer 15

initiator tRNA binds to mRNA through complementary base pairing

Question 16

Prok. docking

Answer 16

GTP is hydrolyzed by IF2. This provides energy for the release of the IFs, and the positioning of tRNAfMet at the P site.

IF3 is released and the 70s is formed.

Question 17

necessary components for protein synthesis elongation

Answer 17

The 70s complex
Charged tRNAs
Elongation factors (EFs; EF-Tu and EF-G)
GTP

Question 18

EF-Tu

Answer 18

binds and transports aminoacyl-tRNA to the ribosome during elongation.

GTP hydrolysis allows the tRNA to enter the A site,

When the anticodon binds the codon, EF-Tu dissociates.

Question 19

Peptidyl transferase

Answer 19

Ribozyme in the 50s

transfers chain at P site onto tRNA’s aa at P site

breaks bond at P, catalyzes formation of peptide bonds at A

Question 20

EF-G

Answer 20

helps move tRNA and mRNA through the ribosome

GTP-form EF-G binds near A site on 50s

GTP hydrolyzed

phosphate release induces movement of A to P and P to E

Question 21

RFs

Answer 21

recognize the stop codon so termination can begin

facilitate termination by releasing the polypeptide and disassembling the translational complex

Question 22

stop codons

Answer 22

UAG, UAA, UGA

Question 23

RF1

Answer 23

UAA, UAG

Question 24

RF2

Answer 24

UAA, UGA

Question 25

RF action

Answer 25

RF at A breaks bond linking the polypeptide to P RF3 forms complex with GTP, binds ribosome RF3 complex releases everything from the ribosome and dissociates subunits

Question 26

eIFs

Answer 26

eukaryotic initiation factors which form the initiation complex eIF4E eIF4G

Question 27

eIF4E

Answer 27

cap-binding protein; binds to 5' cap

Question 28

eIF4G

Answer 28

scaffold protein; interacts with both PABPs and eIF4E

Question 29

cap-binding complex

Answer 29

The cap-binding complex (eIFs, tRNAMet, 40s) explores for the start codon. Identifies proper start by the Kozak sequence

Question 30

closed loop structure

Answer 30

5' cap and 3' tail connect The cap binding protein (eIF4E) binds to the 5' m7G cap. The poly-A binding proteins attach to the 3' poly-A tail. The scaffold protein eIF4G interacts with e1F4E & the binding proteins. This links the 2 ends.

Question 31

Kozak sequence

Answer 31

The Kozak sequence is a consensus sequence surrounding the start codon. The identification of the start codon depends on the Kozak sequence. ribosome binding site on the mRNA

Question 32

Misfolded proteins are generally recognized and degraded. How

Answer 32

tagged for degradation by ubiquitin ubiquitin-tagged protein enters a proteasome proteasome and ubiquitin are recycled, protein broken down in proteasome

Question 33

PRIMARY folding organization level

Answer 33

The sequence of amino acids; a regular polypeptide. This determines the characteristics of higher levels or organization.

Question 34

SECONDARY folding organization level

Answer 34

SECONDARY Parts of the polypeptide form repeating configurations, maintained by H-bonds. alpha helix, beta pleated sheet

Question 35

TERTIARY organization

Answer 35

TERTIARY 3D conformation of the entire chain in space. Results from further arrangement of secondary structures, due to interactions between R groups.

Question 36

QUATERNARY organization

Answer 36

QUATERNARY Applies to proteins composed of multiple polypeptides. Indicates position of the chains in relation to each other.

Question 37

iSOACCEPTING

Answer 37

tRNA same aa, different anticodon