38. INITIATION OF TRANSLATION

Question 1

1. What can be said about the translation of all the mRNAs in a cell?

Answer 1

• they can be translated simultaneously

Question 2

2. What can block the initiation of the translation of selected mRNAs?

Answer 2

• regulatory proteins
• they bind to sequences or structures
• they bind within the untranslated 5’ region of the
  mRNA
• this prevents the attachment of the Ribosomes to the
  mRNA

THIS CAN ALSO BE CAUSED BY:
- Non-Coding RNA

Question 3

3. What are the 4 aspects of Protein Processing that exist to produce functional proteins?

Answer 3

1. Polypeptide Cleavage
2. Protein Folding
3. Subunit Assembly
4. Chemical Modifications

Question 4

4. What is Polypeptide Cleavage?

Answer 4

• some polypeptides are activated by enzymes that
  cleave them
• this happens in the Rough Endoplasmic Reticulum
• EG: insulin

Question 5

5. What is Protein Folding?

Answer 5

• this achieves the tertiary structure of the protein
• it is the formation of disulphide bonds
• this happens in the Rough Endoplasmic Reticulum

Question 6

6. What is Subunit Assembly?

Answer 6

• this forms the Quaternary protein structure
• some polypeptides will come together as the subunits
  of a functional protein
• this happens in the Rough endoplasmic Reticulum
• EG: Haemoglobin

Question 7

7. What is Chemical Modification?

Answer 7

• this is the addition of chemical groups to the proteins
• this forms glycoproteins
• this forms lipoproteins
• some of this happens in the Golgi
• most of this happens in the Rough Endoplasmic
  Reticulum

Question 8

8. What is Protein Degradation?

Answer 8

• this marks a particular protein for destruction
• the cell attaches the protein to Ubiquitin (protein)
• non-functional and mis-folded proteins are also
  attached to the Ubiquitin

Question 9

9. What happens to the Ubiquitinated Proteins?

Answer 9

• they are targeted by the Proteasome
• this degrades them

Question 10

10. What are Proteasomes?

Answer 10

• they are giant protein complexes
• they are 26 S
• they bind to protein molecules
• they degrade them

Question 11

11. What happens to long lived proteins?

Answer 11

• they are degraded in the Lysosome