Translation

Question 1

Major difference between prokaryotic and eukaryotic translation?

Answer 1

Pro-ribosomes start translating before the mRNA is complete

Euk-transcription and translation occur at separate times and in separate locations

Question 2

What are the specialized factors necessary for each stage of translation?

Answer 2

Initiation - IF (initiation factors) + GTP
Elongation - EF (elongation factors) + GTP
Termination - RF (release factors) + GTP

Question 3

What is the initial amino acid in prokaryotes vs. eukaryotes?

Answer 3

Pro- N-formylmethionine

Euk- Methionine

Question 4

Initiation

Answer 4

the small ribosomal subunit binds mRNA

Question 5

what does the small ribosomal subunit bind to in prokaryotes vs. eukaryotes?

Answer 5

Pro- the Shine-Dalgarno sequence in the 5’ UTR of mRNA

Euk- the 5’ cap of mRNA

Question 6

What are the 3 important binding sites in the ribosome?

Answer 6

A-site, P-site, E-site

Question 7

Site in ribosome that holds the incoming aminoacyl-tRNA complex

Answer 7

A-site

Question 8

Site in ribosome that holds the tRNA that carries the growing polypeptide chain

Answer 8

P-site

Question 9

Site in ribosome where the first amino acid binds

Answer 9

P-site

Question 10

A peptide bond is formed as the polypeptide is passed from the tRNA in the _ site to the tRNA in the _ site

Answer 10

between the A- and P- sites

Question 11

What enzyme that is part of the large subunit catalyzes the formation of the peptide bond in translation?

Answer 11

Peptidyl transferase + GTP

Question 12

Site in ribosome where the inactivated (uncharged) tRNA pauses transiently before exiting ribosome

Answer 12

E-site

Question 13

Assist in the locating and recruiting of aminoacyl-tRNA’s along with GTP & also help remove GDP once energy has been used

Answer 13

EF (elongation factors)

Question 14

What does the signal for a secretory peptide (hormones & digestive enzymes) do?

Answer 14

Directs ribosome to move to the ER so the protein can be translated directly into the lumen of the RER and from there the protein can be sent to the Golgi apparatus to be secreted from a vesicle via exocytosis

Question 15

Signal sequences

Answer 15

sequences in proteins that designate a specific destination for them to go to

Question 16

What occurs upon the RF binding to the termination codon?

Answer 16

Molecule of water is added to the polypeptide chain which allows peptidyl transferase and termination factors to hydrolyze the completed pp chain from the final tRNA

Question 17

Special class of proteins that assist in post-translational protein folding

Answer 17

Chaperone proteins

Question 18

What must occur in peptides containing signal sequences before they are able to enter the organelle they were directed to to accomplish their functions?

Answer 18

Signal sequence must be cleaved off

Question 19

4 types of posttranslational modifications?

Answer 19

1. folding by chaperones
2. formation of quaternary function
3. cleavage of proteins with signal sequences
4. covalent addition of other molecules (phosphates, carboxylation, glycosylation, prenylation)

Question 20

Phosphorylation serves what function?

Answer 20

Activation/deactivation of proteins

Question 21

Carboxylation serves what function?

Answer 21

-RCOOH usually serves as Ca2+ binding site

Question 22

Glycosylation serves what function?

Answer 22

determines cellular destination

Question 23

What is prenylation?

Answer 23

The addition of lipid groups to certain membrane bound enzymes