Amino Acids

Question 1

What are the 2 classifications of proteins and include an example of each.

Answer 1

Fibrous proteins - insoluble proteins used to provide strength. eg silk

Globular proteins - soluble proteins used to provide a 3D structure. eg enzymes and hormones

Question 2

Draw the general structure of a protein and the structure of a zwitterion

Question 3

When are disulphide bridges formed?

Answer 3

When a 2 thiol groups are next to each other then a covalent disulphide bridge is formed

Question 4

Why do non-polar amino acids cluster together?

Answer 4

They cannot form hydrogen bonds so the avoid water by forming bonds between each other

Question 5

What are the rules for the primary structure of a protein?

Answer 5

1) no rotation around the planar peptide bonds
2) other parts of the chain must be flexible
3) it must have the maximum amount of rstabalising forces between residues.

Question 6

What is the secondary structure?

Answer 6

Can either be alpha-helix or beta-pleated.
In the alpha-helix, there are approximately 3.6 amino acids per turn.

Question 7

Definition of an oligopeptide

Answer 7

A chain of a few amino acids

Question 8

Where can you find the amino-terminal and the carboxy-terminal on a protein? Draw it out

Question 9

Describe Anfinsen’s experiment

Answer 9

• Broke H bonds by exposing to an urea
• Broke disulfide bridges to expose thiol groups
• Removed urea by dialysis and then bubbled through O2.
• Prove that proetin folding is a spontaneous process, as the protein re-folded and maintained 90% activity.

Question 10

What amino acids are most commonly phosphorylated?

Answer 10

S, Y, T - serine, tyrosine, threonine