Eukaryotic Translation

Question 1

In eukaryotes, transcription and translation are –

Answer 1

separated in space and time

Question 2

With the exception of translation –, the other steps are similar to prokaryotic translation

Answer 2

initiation

Question 3

The nucleolus is a –

Answer 3

ribosome-producing factory

Question 4

More than 80% of cellular RNA is

Answer 4

ribosomal RNA

Question 5

The large subunit (60S) is composed of

Answer 5

3 rRNAs and 49 proteins

Question 6

The small subunit (40S) is composed of

Answer 6

1 rRNA and 33 proteins

Question 7

• Proteins that are in the secretory pathway are synthesized by these ribosomes

Answer 7

membrane attached
• Are bound to the rough
endoplasmic reticulum (ER)

Question 8

Proteins in the non- secretory pathway are synthesized by these ribosomes

Answer 8

membrane unattached, free in cytosol

Question 9

What is the first amino acid?

Answer 9

methionyl-tRNAimeth

Question 10

How does a ribosome know where to start translation on an mRNA?

Answer 10

The small subunit and initiation factors recognize the 5􏰁cap of the mRNA.

Question 11

mRNA contains a translation initiation sequence called the

Answer 11

Kozak sequence

Question 12

Kozak sequence is a – that includes the AUG start codon.

Answer 12

7 nucleotide sequence

Question 13

The – are most critical determinants of the Kozak sequence.

Answer 13

first A, AUG, and last G

Question 14

Kozak sequence usually located

Answer 14

100 nt from the 5’cap

Question 15

Eukaryotic initiation factors (eIFs), – bind to the small and large ribosomal subunits respectively to prevent them from binding to each other without mRNA

Answer 15

eIF3 and eIF6

Question 16

• Ternary complex is formed:

Answer 16

eIF2-GTP + met- tRNAimet

Question 17

– subunit form the preinitiation complex

Answer 17

eIF1A, ternary complex, and eIF3-40S

Question 18

Cells can regulate protein synthesis by phosphorylating a –.

Answer 18

serine residue on the eIF2 bound to GDP

Question 19

The phosphorylated complex is unable to exchange the bound GDP for GTP and – thus inhibiting protein synthesis

Answer 19

cannot bind Met-tRNAiMet,

Question 20

As the mature mRNA is transported from the nucleus into the cytoplasm, – for protein synthesis binds to the 5’cap

Answer 20

initiation factors (IF4s)

Question 21

– binds to the mRNA-eIF4E complex to form the initiation complex through an interaction of the eIF4G subunit and eIF3.

Answer 21

Preinitiation complex

Question 22

The – then scans along the mRNA to look for the Kozak sequence containing the first AUG

Answer 22

initiation complex

Question 23

As the initiation complex scan the mRNA, –, which is activated by eIF4B, uses ATP to unwind RNA structures

Answer 23

the helicase eIF4A

Question 24

Scanning stops as the – recognizes the AUG codon (Kozack sequence).

Answer 24

met-tRNAimet anticodon

Question 25

eIF2-GTP hydrolyzes to eIF2-GDP, an – that prevents further scanning.

Answer 25

irreversible step

Question 26

eIF5 helps bring in–; GTP is

hydrolized and the IFs are released

Answer 26

60S-eIF6

Question 27

elongation

Answer 27

• Entry of each succeeding aminoacyl-tRNA -Formation of a peptide bond
• Movement, or translocation, of the ribosome one codon at a time along the mRNA.

Question 28

Elongation factor – brings in the new aminoacyl-tRNA at the A site.

Answer 28

EF1α-GTP

Question 29

Binding of the anticodon with the codon hydrolyzes the GTP of –.

Answer 29

EF1α- GTP

Question 30

The 1st peptide bond formation is catalyzed by the peptidyl transferase activity of the

Answer 30

large rRNA of the large 60S subunit

Question 31

rRNA is a

Answer 31

ribozyme

Question 32

The carboxyl end of the amino acid at the P site is joined to the amino end of the amino acid at the A site to form the .

Answer 32

peptide bond

Question 33

Translocation of the ribosome one codon down the mRNA requires hydrolysis of

Answer 33

EF2-GTP

Question 34

Initiator tRNA without the aa is moved to the – and the 2nd aa-tRNA is moved to the –

Answer 34

Initiator tRNA without the aa is moved to the E site and the 2nd aa-tRNA is moved to the P site

Question 35

When the ribosome reaches the stop codon, release factors – enter the A site

Answer 35

eRF1 and eRF3- GTP

Question 36

– recognizes all the stop codons.

Answer 36

eRF1

Question 37

eRFs promote cleavage of the peptide chain from – through hydrolysis of GTP.

Answer 37

the last tRNA in the P site

Question 38

E. coli cells divide

Answer 38

every 20 min

Question 39

Prokaryotes: – Can transcribe and translate all at the

same time and place

Answer 39

20 aa/sec.

Question 40

Eukaryotes: – mRNA processing, traveling, etc.

Can have multiple translation processes occurring at once…

Answer 40

3-5 aa/sec.

Question 41

the complex of mRNA and multiple ribosomes

Answer 41

Polyribosome (or polysome)

Question 42

The polyA tail also functions to –.

Answer 42

enhance translation efficiency

Question 43

– associates with eIF4G to form a circular mRNA.

Answer 43

PolyA binding protein (PABP)

Question 44

mRNA with premature stop codons are

Answer 44

targeted for degradation

Question 45

premature mRNAs are usually translated only once before being destroyed through

Answer 45

nonsense mediated decay (NMD)

Question 46

is bound 20-24 bp upstream of where two exons have been joined by splicing

Answer 46

The Exon-Junction Complex (EJC)

Question 47

The EJCs remain bound to the mRNA until displaced by an advancing –

Answer 47

ribosome during translation