29. ELONGATION OF TRANSLATION

Question 1

1. What happens during elongation?

Answer 1

• amino acids are added one by one
• to the preceding amino acids
• they are added at the C-terminus of the growing
  polypeptide chain

Question 2

2. What does each addition of an amino acid involve?

Answer 2

• it involves proteins
• these are known as Elongation Factors

Question 3

3. What are the 3 steps of the Elongation of Translation?

Answer 3

1. Codon Recognition by the tRNA
2. Peptide Bond Formation
3. Translocation

Question 4

4. What happens when the Codon is recognised by the tRNA?

Answer 4

• there is a transfer of the Aminoacyl-tRNA
• from the cytosol
• to position A of the ribosome

Question 5

5. What happens when the Peptide bond forms?

Answer 5

• there is an attachment of new amino acids
• they are attached to the growing polypeptide chain
• they are attached by peptide bond

Question 6

6. What happens during Translocation?

Answer 6

• the tRNA molecule translocates from position A
• to position P
• the mRNA moves 3 nucleotides
• ( 1 codon)

Question 7

7. What is Peptide Bond formation?

Answer 7

• this bond forms between the Amino Acid at position A
  and the Polypeptide chain at Position P
• the uncharged tRNA is left at position P

Question 8

8. What is Peptidly Transferase?

Answer 8

• this is part of the large ribosomal subunit
• this is known as the Riboenzyme
• this enzyme catalyses peptide bond formation

Question 9

9. What happens to the uncharged tRNA at position P during Elongation?

Answer 9

• it will be transferred to Position E

Question 10

10. What do the elongation factors do?

Answer 10

• they provide energy for translocation
• they do this by the hydrolysis of GTP

Question 11

11. What is Translation Termination?

Answer 11

• this happens when a stop codon in the mRNA
  reaches the A site of the ribosome

Question 12

12. What happens when a stop codon joins the Ribosome at point A?

Answer 12

• the A site will accept a release factor
• this factor promotes the hydrolysis between the tRNA
  in the P site and the last amino acid on the chain
• this releases the polypeptide
• the peptide bonds are broken
• the two ribosomal sub units will separate

Question 13

13. What is the Mode of Action of Rifampicin?

Answer 13

• it is used to treat TB
• it inhibits bacterial RNA polymerase
• TRANSCIPRTION

Question 14

14. What is the mode of action of Tetracyclines?

Answer 14

• they bind 30S Ribosomal subunits
• they inhibit amino-acyl (A site) tRNA attachment
• TRANSLATION

Question 15

15. What is the mode of action of Aminoglycosides?

Answer 15

• they bind 30S subunits
• inhibit initiation complex formation
• TRANSLATION

Question 16

16. What is the mode of action of Chloramphenicol Clindamycin?

Answer 16

• they inhibit 50S peptidyl-transferase
• inhibit peptide bond formation during elongation
• TRANSLATION

Question 17

17. What is the mode of action of Macrolides?

Answer 17

• they block the elongation step of Translation
• TRANSLATION

Question 18

18. What produces Alpha Amantinin?

Answer 18

• this is produced by poisonous mushrooms

Question 19

19. What relation does Alpha Amantinin have to gene expression?

Answer 19

• inhibits RNA Polymerase II

Question 20

20. What is Diphtheria Toxin?

Answer 20

• this is a bacterial toxin

Question 21

21. What relation does the Diphtheria Toxin have to gene expression?

Answer 21

• it inhibits EF-2
• it inhibits the translocation step of Translation