OSMT (Ontario Society of Medical Technologists) Practice Exam

How many amino acids does a heavy chain typically have?

1. a. 100 amino acids

2. b. 200 amino acids

3. c. 300 amino acids

4. d. 400 amino acids

The correct answer is: d. 400 amino acids

The typical length of a heavy chain in immunoglobulins, which are essential components of the immune system, ranges around 400 amino acids. Heavy chains consist of a variable region that contributes to antigen specificity and a constant region that determines the class of the antibody (IgG, IgA, IgM, IgE, IgD). While smaller proteins might contain around 100 to 200 amino acids, heavy chains are larger due to their crucial functions in binding to antigens and interacting with other components of the immune system. The more complex structure of heavy chains accounts for their greater size compared to lighter chains or other smaller proteins. Thus, a heavy chain typically consists of approximately 400 amino acids, making this the correct answer.