Protein Structure

Question 1

Predominant form of chiral amino acids in nature

Answer 1

L-amino acids

Question 2

Isoelectric point

Answer 2

pH at which amino acid’s net charge equals 0 (zwitterionic form)

Question 3

Features of peptide bond

Answer 3

Effectively planar: push O away from N

Functional groups as well as alpha carbons are usually on opposite sides of the peptide bond from each other

Question 4

Phi torsion angle

Answer 4

Angle between carbonyl carbons

Found by looking down nitrogen/alpha carbon bond

Question 5

Psi torsion angle

Answer 5

Angle between amines

Found by looking down alpha carbon/carbonyl carbon bond

Question 6

Steric exclusion of torsion angles

Answer 6

Plotted on Ramachandran plot
Few rotations of peptide bond are allowed
If this were not present, there would be too much entropy to overcome to have regular protein folding

Question 7

Secondary structure

Answer 7

Hydrogen bonds between the atoms of the amino and carboxyl groups

Question 8

Secondary structure is a natural consequence of…

Answer 8

Limited torsion angles

Question 9

Tertiary structure

Answer 9

Folding of complete protein

Caused by side chain interactions

Question 10

Seeding effect

Answer 10

Correct positioning of 1 portion of peptide is locked in place and drives other portions to position correctly

Question 11

Quaternary structure

Answer 11

Multiple subunits (polypeptide chains) of protein together