Protein Folding And Stability

Question 1

What causes neurodegenerative diseases?

Answer 1

Incorrect protein folding

Question 2

Outline cystic fibrosis

Answer 2

-involves the mix folding of a protein called CFTR
-protein regulates the transfer of chloride and sodium across the cell membranes
-disruption of chloride and sodium transfer leads to sticky mucus to build up in the lungs and digestive system

Question 3

What does the protein CFTR regulate

Answer 3

Transfer of chloride and sodium across the cell membranes

Question 4

Give examples of diseases associated with improper folded proteins

Answer 4

Alzheimer’s disease
Parkinson’s disease
Huntington’s disease
Cystic fibrosis

Question 5

What are plaques/ amyloid fibrils?

Answer 5

Deposition of protein aggregates

Question 6

Reason for correlation of disease increasing with age:

Answer 6

As we age the delicate balance of synthesis, folding and degradation of proteins is disturbed, which results in the production and accumulation of misfolded protein aggregates.

Question 7

What is CJD

Answer 7

-human prion disease
-neurological disease
-rapid progression
-fatal within 1 year of infection

Question 8

What is CJD caused by?

Answer 8

An abnormal isoform of a cellular glycoprotein known as the prion protein

Question 9

What can cause proteins to denature, unfold and aggregate with other misfolded proteins?

Answer 9

A change in pH or an increase in the temperature of the surrounding environment

Question 10

What are the forces that stabilise the 3D structure of proteins?

Answer 10

-hydrophobic interactions
-ionic interactions
-disulphide bridges
-van der waals
-hydrogen bonding

Question 11

What is entropy:

Answer 11

A measure of the degree of randomness or disorder in a system
- the total entropy of a system plus that of its surroundings always increases

Question 12

What are clathrate structures:

Answer 12

When the water molecules come into contact with the non-polar molecules, they form cages (clathrate structures) around them, in an ordered manner compared to water molecules alone

Question 13

Outline hydrophobic interactions

Answer 13

Non-polar molecules tend to associate with each other in water compared with other less polar solvents. This tendency is called the hydrophobic effect and the associated interactions are called hydrophobic interactions.

Question 14

What are ionic interactions?

Answer 14

Electrostatic interactions that occur between a positively charged amino acid residue and a negatively charged amino acid residue

Question 15

What are van der waals

Answer 15

Molecules that do not have a permanent dipole interacting with each other and having an attractive force between those molecules. (Induced dipoles)
Intermolecular forces between atoms and between non-polar molecules as a result of the motion electrons

Question 16

What is a hydrogen bond

Answer 16

Electrostatic attraction created between a partially positively charged hydrogen atom attached to a highly electronegative atom and another nearby electronegative atom
Type of dipole- dipole interaction

Question 17

What is an a-helix

Answer 17

Right handed coil of amino-acid residues on a polypeptide chain, typically ranging between 4 and 40 residues. This coil is held together by hydrogen bonds between the oxygen of carbonyl group and the hydrogen of amine group

Question 18

What is in a beta sheet

Answer 18

Two or more polypeptide chains run alongside each other and are linked in a regular manner by hydrogen bonds between the main chain carbonyl and amine groups
The sheets can have a rippled or pleated appearance. There is no bonding within the chain rather there is bonding across the chain.

Question 19

What do the polar groups do in an unfolded protein

Answer 19

Hydrogen bonded to and partially surrounded by water molecules

Question 20

What do the polar groups do in a folded protein

Answer 20

Most polar groups will form one or more intramolecular hydrogen bonds and will be surrounded by the polar and nonpolar groups that make up the interior of a folded protein

Question 21

What are disulphide bonds

Answer 21

Covalent bonds formed between two cysteine or methionine by oxidation reactions
Not present in the unfolded state but are in the folded state

Question 22

When did Christian anfinsen conduct his series of experiments?

Answer 22

1950

Question 23

What are molecular chaperones

Answer 23

A class of proteins that aid in the correct folding of other proteins in vivo
Stabilise unfolded proteins, unfold them for translocation across membranes or for degradation, and/ or to assist in their correct folding and assembly.
Stop newly synthesis proteins from aggregating