Protein structure

Question 1

Primary structure

Answer 1

• a linear arrangement of AAs
• coded in the DNA
• N -terminus to C-terminus
• stabilized by the covalent peptide bonds between AA
• primary structure alone encodes all the information for all the higher level protein structure
• 2/3/4 degree structures are energetically most favorable arrangement of the primary structure

Question 2

secondary structure

Answer 2

results from the hydrogen bonds between near by AA

Question 3

most common protein secondary structures

Answer 3

alpha helix

beta-pleated sheets

Question 4

alpha helix

Answer 4

-peptide chains coils clockwise around a central axis
-helix is stabilized by intra molecular hydrogen bond
between carbonyl O atom [nth]& an amide H atom[n+4 th] ,4 residues down the chain

Question 5

Beta -sheets

Answer 5

can be parallel or antiparallel

peptide chains lie along one another forming rows
stabilized by the intra molecular hydrogen bond between the carbonyl oxygen and amide H atom in the adjacent chain

R- group of the amino residue points above and below the plane of the beta sheets

Question 6

Secondary structure & Proline

Answer 6

due to its cyclic structure, it will introduce knick in the peptide chain

thus rarely found in alpha helix-except in helicase that crosses the cell membrane
like wise rarely in the middle of the Beta- sheets

Question 7

Tertiary structure

Answer 7

3D

determined by hydrophilic and hydrophobic interactions between R -groups

Question 8

Tertiary structure’s 3D is determined by

Answer 8

1. Hydrogen bond

2. acid-base interactions between AA w charged R-groups, creating salt bridge