L7

Question 1

What degrades unfolded proteins that aren’t fixed by molecular chaperones?

Answer 1

Protease

Question 2

What are heat shock proteins?

Answer 2

Molecular chaperones which come about when heat stress happens in a cell (causing protein unfolding, (hydrophobic regions exposed)).

Chaperone binds to protein, with ATP hydrolysis, tight binding and conformation changes occur in the chaperone, pulling protein back into structural alignment. Chaperone dissociates.

Question 3

Why are abnormally folded proteins dangerous?

Answer 3

They aggregate due to hydrophobic surfaces and cause diseases.

Eg. Amyloid in Alzheimer’s

These aggregates may be resistant to proteolysis.

CROSS BETA FILAMENTS R BAD

Question 4

How are mis folded proteins destroyed?

Answer 4

Via proteosome - ATP dependNt enzyme complex

Recognises target protein with polyubiquitin chain

Question 5

What do molecular chaperones do?

Answer 5

Assist the refolding of intermediate structures that would otherwise be discarded.

Question 6

How is ubiquitin added to protein?

Answer 6

• Ubiqutin activating enzyme (E1) binds to ubiquitin
• E1 interacts with E2 and E3 Ubiqutin ligase and transfers ubiquitin to E2
• degradation signal recognise on a target protein by e3
• E2 and E3 transfer ubiquitin to target protein

Process is repeated to create chain of ubiquitin for proteosome to recognise

Question 7

What is insulin’s folding mechanism?

Answer 7

It is synthesised as a single chain, inactive proinsulin.
Stabilised by disulfide bonds, the protein is cleaved into its active form

(two seperate chains)

Question 8

What is phosphorylation?

Answer 8

The addition of a phosphate group by protein kinase.

Causes either major conformational changes that activates/inactivates a protein, or generated a binding site.

Demonstrates how proteins can act as switches.

Question 9

What is glycosylation?

Answer 9

Process where extracellular proteins have complex sugar groups or oligosaccharides added.

• > creates fuzzy layer
• > assists generating binding sites for secreted factors
• > gives cell chemically resistant & slippery layer

Question 10

What does the term localisation refer to?

Answer 10

The way that proteins need to be in the correct location in the cell in order to function

Proteins can move due to the receipt of a signal