Proteins 2

Table of Contents
Biomolecules Gateway Page
Jmol Tutorial

In this module:

Secondary Structure
α Helices
ß Sheets
Tertiary Structure
Disulfide Bonds, Domains
Cofactors, Quaternary Structure
Protein Folding
Alzheimer's and "Mad-Cow" Diseases


After completing this module, you should be able to:

  • Describe proteins in terms of primary, secondary, tertiary, and quaternary structure
  • Describe α helices and ß sheets
    • Point out similarities
    • Point out differences
  • Recognize some common motifs and give examples of proteins that contain them
  • Describe how disulfide bonds affect the tertiary structure of proteins
  • Give examples of proteins composed of domains
  • Describe how quaternary structure allows cooperativity and allosteric effects

Primary Structure

As discussed in the Protein 1 module, proteins have a specific sequence of amino acids, starting from their N-terminus and proceeding to their C-terminus. This sequence is called the protein's primary structure . As the structures of hemoglobin (left) and ribonuclease (right) below show, however, there is a lot more to a protein's structure than just its primary structure. Scientists divide this structure into four broad hierarchical levels: primary, secondary, tertiary, and quaternary.

Proteins 2