30. POST TRANSLATIONAL MODIFICATIONS

Question 1

1. What are Post-Translational modifications?

Answer 1

• polypeptide chains are modified after translation
• this makes them functional

Question 2

2. What is Protein Targeting?

Answer 2

• completed proteins are then transported to specific
  sites
• in cells or organisms

Question 3

3. How do Polypeptides achieve their final, tertiary structure?

Answer 3

• they spontaneously fold into their 3D shapes

Question 4

4. How can we modify certain amino acids?

Answer 4

• addition of sugar
• addition of lipids
• addition of phosphate groups

Question 5

5. How can we activate polypeptides?

Answer 5

• some polypeptides are activated by enzymes that
  cleave them

EG:
- insulin is synthesised as a polypeptide
- enzyme cuts out the middle part of the chain
- creates 2 polypeptide chains
- that are joined together by Disulphide bonds

Question 6

6. What happens when polypeptide subunits come together?

Answer 6

• they from the subunits of a protein
• this is the quaternary structure

Question 7

7. Where does Polypeptide synthesis always begin?

Answer 7

• it always begins in the Cytosol

IT CAN ALSO END IN THE CYTOSOL:
- for cytosolic proteins that are synthesised by free
ribosomes

Question 8

8. What can be said about the polypeptides that are designed to be synthesised in the Endoplasmic Reticulum?

Answer 8

• they are marked with a signal polypeptide
• this is a sequence of about 20 amino acids at the end
  of the polypeptide
• this signals the ribosome to attach to the ER
• it becomes a bound ribosome

THIS SIGNAL IS SENT TO A SIGNAL RECOGNITION PARTICLE:
- (SRP)
- this helps the polypeptide and the ribosome to be
transferred to the ER

Question 9

9. What is the RNA Vaccine?

Answer 9

• this is also known as a Nucleoside Modified RNA
  vaccine (mRNA)

Question 10

10. What happens in the mRNA vaccine?

Answer 10

• there is synthetic mRNA
• some nucleosides are replaced by other naturally
  modified nucleosides
• they can also be replaced by synthetic nucleoside
  analogues

Question 11

11. What is the mRNA encapsulated in?

Answer 11

• it is encapsulated in a lipid nanoparticle

Question 12

12. What does the mRNA code for?

Answer 12

• it encodes for a mutated form of the spike protein
  of the SARS-CoV-2
• this triggers an immune response against infection
• this is due to the virus protein