1. Four Levels of Protein Structure

2. Four Levels of Protein Structure
Primary Structure:
Linear Sequence of Amino Acids
Each amino acid has
central carbon liked to
---hydrogen (H)
---amino group (NH2)
---acid group (COOH)
---unique group (R) O H
H2N C C R OH

4. The carboxyl group of one amino acid is linked 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. O H H H O
H2N C C N C C OH R1 R2

6. Four Levels of Protein Structure
Secondary Structure:
Folded structure due to hydrogen bonds between the amino and acid groups of amino acids N C N C H H O O or O H O H C N C N

7. Four Levels of Protein Structure
Tertiary Structure:
Three dimensional folded structure due to attractions and repulsions between R groups
All but peptide bonds are involved in tertiary structure.

9. Four Levels of Protein Structure
Quaternary structure:
Association of two or more protein chains
eg. Hemoglobin is composed of protein chains
2 are called alpha hemoglobin are called beta hemoglobin

10. Applying Your Knowledge
Primary
Secondary
Tertiary
Quaternary
Which structure results exclusively from hydrogen bonding?
Which structure involves an association of two or more protein chains?
Which structure describes the linear sequence of amino acids?
Which structure depends upon interactions between the R groups of the amino acids?