Question

Which one of the following is NOT true of the constant (C) regions of antibodies? A. The constant regions determine the specific type of antibody class formed. B. The constant regions form an antigen-binding site. C. The constant regions determine how an antibody class will carry out its immune role. D. The constant regions form the ""stem"" of an antibody. E. The constant regions are the same or nearly the same on all antibodies.

Answer 1

The correct answer is B. The constant regions do not form an antigen-binding site.

Step-by-step explanation:

Antibodies, also known as immunoglobulins, play a crucial role in the immune system by recognizing and binding to specific antigens. The structure of antibodies consists of variable (V) and constant (C) regions. The V regions, located at the tips of the Y-shaped antibody molecule, are responsible for antigen binding and specificity. On the other hand, the C regions make up the constant backbone of the antibody.

Option B is incorrect because it states that the B. constant regions form an antigen-binding site. This is inaccurate as the antigen-binding sites are exclusively located in the variable regions. These variable regions exhibit high diversity, allowing antibodies to recognize a wide range of antigens. The constant regions, while important for the overall structure and function of antibodies, do not directly participate in antigen binding. Instead, they determine the class of antibody (IgM, IgG, IgA, IgD, or IgE) and influence how the antibody carries out its immune role, such as activating complement or binding to immune cells.

In summary, the constant regions of antibodies provide structural stability and determine the antibody class, but they do not contribute to antigen binding. This clarification is essential for understanding the distinct roles played by variable and constant regions in the functioning of antibodies within the immune system.

Answer 2

Option (B) is the correct answer.

The constant (C) regions of antibodies have several well-defined roles, but they do not form the antigen-binding site.

The antigen-binding site is formed by the variable (V) regions of the antibody's heavy and light chains.

Therefore, the statement that is NOT true about the constant regions of antibodies is: B. The constant regions form an antigen-binding site.

The constant regions are involved in determining the class of antibody (IgA, IgD, IgE, IgG, or IgM), determining how an antibody will carry out its immune role, forming the "stem" of the antibody (the Fc region), and being consistent across antibodies of the same class.

But they are not involved in the specific antigen-binding function; that is the role of the variable regions.