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.


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 a 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.

We’ll be using as our main source of information on collagen. This site is a Protein Data Bank where you can search for any information about your favorite proteins, including everyone’s favorite, collagen.

Click on this Molecule of the Month: Collagen link to view the article on 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 in collagen?

-The primary structure of Collagen are in order of amino acids. Collagen is three chains wound together to make a triple helix and is made up of three amino acids which form a sturdy structure. The amino acids are proline, hydroxyproline and every third one is glycine. 

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?

-Vitamin C is a reaction from Hydroxyproline when it is created by modifying normal proline amino acids, which is critical for collagen stability. If you don’t get enough Vitamin C in your diet it can lead to the slowing down of your hydroxyproline which stops the construction of new collagen to form.

3. Describe the quaternary structure of collagen (the way in which the polypeptide chains are arranged).

-The quaternary structure of Collagen is made up of three chains that are winded together to make the triple helix. It is said to be the left-handed helix which is the opposite of an alpha helix.

Part 2.

Use your browser to go to the Web site of the Osteogenesis Imperfecta Foundation at

On the left side of the home page, click the link “About OI”, then find the “Facts About OI” section.

Read the material in the sections entitled "Facts on Osteogenesis Imperfecta” and “Types of OI.” 

Read this handout (pdf)  from the resources section on Bone Structure.

Use what you have learned to answer the following questions:

1. Describe the role of collagen in bones. Why do collagen problems lead to bone problems?

  -Collagen in the bones is supported by the calcium and phosphorus in the blood, that crystallizes and surrounds the collagen and gives the bone strength. Collagen problems for example are diseases and it makes the collagen abnormal to where the bones become brittle.   

2. What is the main symptom of osteogenesis imperfecta?  What are some other symptoms that people with OI may have?

-The main symptom of osteogenesis imperfecta is because the collagen can not give the skeleton full strength due to the quantity or shape which is abnormal, which also can be because of the mutation or change in the DNA.  

3. 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?

-Type 1 of osteogenesis imperfecta is where collagen forms abnormal molds and affects the bone to where it has fewer problems. Compared to types 2 and 3, where they have more problems due to the collagen being more susceptible to the body and destroying the molecules. Also, these bad collagen molecules start to be transferred to the outer cell, creating abnormal collagen fibers. 

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