Proteins and their functions

Question 1

Briefly describe the 4 structures of proteins

Answer 1

primary - specific sequence of amino acids
secondary - folding, alpha helix, beta pleated sheet
tertiary - 3D folding
quaternary - more than one polypeptide chain

Question 2

Name the 4 regulated processes of protein function

Answer 2

synthesis
localisation
modification
degradation

Question 3

What is constitutive secretion?

Answer 3

Constant secretion, transport vesicles

No storage, no secretory vesicles

Question 4

Where are proteins modified?

How can they be modified?

Answer 4

• in the ER
  disulphide bonds
  glycosylation
• further modified in golgi apparatus

Question 5

What do proteins contain to direct them it to the correct site in the cell?
How do they move from the cytosol into organelles?

Answer 5

sorting signal

tranporters

Question 6

How are proteins controlled?

Which enzymes are involved?

Answer 6

• phosphorylation of amino acid side chains activates/inactivates a protein
• induces conformational change
• reaction catalysed by protein kinase
• dephosphorylation by protein phosphatase

Question 7

What is the unfolded protein response?
What effect does an imbalance in this process have?
What conditions are associated with an imbalance?

Answer 7

• a homeostatic response to keep cells folding capacity in balance with its needs, takes away unfolded proteins
• ER stress and increase in unfolded proteins
• this can inhibit translation and lead to cell death
• alzheimer’s, CJD, parkinsons

Question 8

What are amyloidoses and prion diseases caused by?

Answer 8

• imbalance in unfolded protein response
• caused by mis-folding aggregation and accumulation of protein
• immune response directed at protein

Question 9

Cystic fibrosis related to proteins and their funciton

Answer 9

• deletion mutation
• misfolded protein
• retained in ER
• degraded and so never reaches the membrane