COLLAGEN STRUCTURE AND FUNCTION

Proteins are the most diverse class of biological molecules. Most of your body is made up of proteins. Each protein consists of one or more polypeptide chains, in which amino acids are strung together in a specific order. This amino acid sequence or "primary structure" is the key to the shape and function of the protein. Interactions among different amino acids along the length of the polypeptide chain cause it to coil, bend, and fold into a complex shape.

Some proteins consist of two or more polypeptide chains. In many cases, the polypeptide chains form a rounded or globular shape. Most enzymes are like this, as is the oxygen-carrying hemoglobin molecule. In other cases, polypeptide chains form long strands or sheets. These fibrous proteins are often structural components, such as keratin and collagen.

ACTIVITY

In this activity, you will explore the structure and function of collagen, the most abundant protein in the human body. You will begin by visiting the Protein Data Bank site, where the structure of collagen is described and illustrated in a "Molecule of the Month" feature. Next, you will research the effects of osteogenesis imperfecta (OI), a genetic disorder that affects the structure or number of collagen molecules.

Part 1.

Use your browser to go to http://www.pdb.ufmg.br/pdb/molecules/pdb4_1.html. This April 2000 Molecule of the Month feature is about collagen. Read the information and view the graphics. Use this information to answer the following questions:

  1. Describe the primary structure of collagen. What are the major amino acid components?
  2. What role does vitamin C play in collagen formation? What happens when a person does not get enough vitamin C in his or her diet?
  3. Describe the quaternary structure of collagen (the way in which the polypeptide chains are arranged).

Part 2.

Use your browser to go to the Web site of the Osteogenesis Imperfecta Foundation at http://www.oif.org/. Click the "About OI" link on the menu at the left to access and information on OI. Read the material in the sections entitled "Fast Facts" and "Understanding Bone Structure." Use what you have learned to answer the following questions:

  1. What is the main symptom of osteogenesis imperfecta?
  2. Type I osteogenesis imperfecta causes fewer problems than the other forms. How does the collagen structure in Type I OI differ from that of the other types?
  3. Describe the role of collagen in bones. Why do collagen problems lead to bone problems?