2. Four Levels of Protein
Structure
• Primary Structure:
Linear Sequence of Amino Acids
C CH2N
H
R
Each amino acid hasEach amino acid has
central carbon liked tocentral carbon liked to
---hydrogen (H)---hydrogen (H)
---amino group (NH---amino group (NH22))
---acid group (COOH)---acid group (COOH)
---unique group (R)---unique group (R)
O
OH
3.
4. The carboxyl group of one amino acid is linkedThe carboxyl group of one amino acid is linked
to the amino group of the next amino acid.to the amino group of the next amino acid.
5. Four Levels of Protein
Structure
• Primary Structure:
Amino Acids are linked with a covalent
bond called a peptide bond.
C CH2N
H
R1
O
N C C
O
OH
H
R2
H
6. Four Levels of Protein Structure
• Secondary Structure:
Folded structure due to hydrogen bonds
between the amino and acid groups of
amino acids
C
O
N
H
C
O
N
H
C
O
N
H
C
O
N
H
or
7. Four Levels of Protein Structure
• Tertiary Structure:
Three dimensional folded structure due to
attractions and repulsions between R
groups
All but peptide bonds areAll but peptide bonds are
involved in tertiary structure.involved in tertiary structure.
8.
9. Four Levels of Protein Structure
• Quaternary structure:
Association of two or more protein chains
eg. Hemoglobin is composed ofeg. Hemoglobin is composed of
4 protein chains4 protein chains
2 are called alpha hemoglobin2 are called alpha hemoglobin
2 are called beta hemoglobin2 are called beta hemoglobin
10. Applying Your Knowledge
A. Which structure results exclusively from
hydrogen bonding?
B. Which structure involves an association of two
or more protein chains?
C. Which structure describes the linear sequence
of amino acids?
D. Which structure depends upon interactions
between the R groups of the amino acids?
1. Primary
2. Secondary
3. Tertiary
4. Quaternary
