1. Primary Structure: Polypeptide chain Polypeptide chain Amino acid monomers Peptide linkages Figure 3.6 The Four Levels of Protein Structure.

1. Primary Structure: Polypeptide chain

Polypeptide chain

Amino acid monomers

Peptide linkages

Figure 3.6 The Four Levels of Protein Structure

2. Secondary Structure:a. Helix

1. Primary Structure: Polypeptide chain

Hydrogen bond

Figure 3.6 The Four Levels of Protein Structure

2. Secondary Structure:a. Helix

1. Primary Structure: Polypeptide chain

b. Pleated sheet

Hydrogen bond

Figure 3.6 The Four Levels of Protein Structure

3. Tertiary Structure: Polypeptides fold

2. Secondary Structure:a. Helix

1. Primary Structure: Polypeptide chain

b. Pleated sheet

Disulfide bond

Pleated sheet

Helix

Figure 3.6 The Four Levels of Protein Structure

4. Quaternary Structure: Polypeptides assemble into larger molecules3. Tertiary Structure: Polypeptides fold

2. Secondary Structure:a. Helix

1. Primary Structure: Polypeptide chain

b. Pleated sheet

Figure 3.6 The Four Levels of Protein Structure