5.6 Steps of Translation

Question 1

What occurs during the first part of translation?

Answer 1

all parts are assembled at the ribosome

Question 2

How does the ribosome look until translation is ready to be commenced?

Answer 2

two separate subunits

Question 3

What is the first step of translation called?

Answer 3

initiation

Question 4

What are the three parts of the ribosome?

Answer 4

aminoacyl site (A)
peptidyl site (P)
exit site (E)

Question 5

What are the molecules needed at the initiation site at the ribosome?

Answer 5

mRNA stranded
charged tRNA
three protein initiation factors

Question 6

What is the first step of initiation of translation?

Answer 6

binding of three protein initiation factors to the small ribosomal subunit which will then bind the mRNA strand

Question 7

What is the modified amino acid that bacterial initiation codon encodes for?

Answer 7

fMet (n-formylmethionine)

Question 8

What is the Shine-Delgarno Sequence?

Answer 8

short sequence of mRNA (AGGAGG) just upstream of the initiation AUG

Question 9

What is the function of the Shine-Delgarno Sequence?

Answer 9

acts as a recruiter for the small ribosomal subunit and helps in recognition and binding to the initiation codon

Question 10

Where does the first tRNA holding the complementary sequence to AUG bind?

Answer 10

peptidyl site on the ribosome

Question 11

What happens once the first tRNA binds to the peptidyl site?

Answer 11

IF3 is released and the large subunit binds to the rest of the complex forming the 70s initiation complex

Question 12

What happens once the 70s initiation complex is formed?

Answer 12

the other two IFs are released opening the aminoacyl site for subsequent amino acids

Question 13

What is the second step of translation known as?

Answer 13

elongation

Question 14

What escorts the next tRNA to the aminoacyl site?

Answer 14

elongation factor protein EF-tu

Question 15

What does it mean for elongation factor to be GTP-ases?

Answer 15

they are linked to a molecule of GTP which will be hydrolyzed to GDP when the tRNA containing the amino acid is bound to the A site

Question 16

What does hydrolyzing of the GTP bound to the elongation factor cause?

Answer 16

conformational change within the elongation factor to release the tRNA into the A site

Question 17

How are the amino acids sitting in the peptidyl and aminoacyl site bonded together?

Answer 17

the tRNA in the peptidly site will hydrolyze and break its high energy ester bond with the amino acid which will provide the energy for a peptide bond to form between the two amino acids

Question 18

Where does the tRNA from the peptidyl site move to once it releases its amino acid?

Answer 18

exit site E

Question 19

What is the process of translocation?

Answer 19

when the mRNA-tRNA+2 amino acid complex shifts towards the P site by a distance of three nucleotides

Question 20

What assists in the process of translocation?

Answer 20

a GTP-ase elongation factor EF-G