Chapter 37, Problem 1AC

Why is it essential that antibodies and T-cell receptors bind only large molecules (such as proteins) and not small molecules (such as amino acids)?

Summary Introduction

To determine:

The reason that why it is essential for antibodies and T cell receptors to bind only to large molecules and not to small molecules.

Introduction:

The end of each arm of heavy and light chain consists of variable region which provides a site for antigen binding. The amino acid sequences of variable regions of the antibody are different in all antibody molecules. Due to this, each antigen has its specific antibodies and each antibody binds to a specific antigen. By recognizing an antigen of a specific type a specific antibody is released to target it which makes an immune response more effective.

Explanation of Solution

An immunogen is that organism or pathogen which is responsible for stimulating an immune response in the body. An immunogen must have three characteristics in order to evoke an immune response. They should have high molecular weight, foreignness, and chemical complexity in order to be recognized and binding with the antibodies.

Antibodies along with other target-specific immune cells like T cell receptors bind to large molecules only. It is because the antigen or pathogens have a large pattern of peptide chain some part of which may resemble amino acid sequences of other essential proteins of the body. To avoid any confusion or overreaction of immune cells in the body, the antibodies bind to large molecules rather than small molecules. Also, small molecules do not facilitate cross-linking of antibodies and could

If target-specific immune cells attack small molecules like amino acids, there could be the destruction of normal cells by the antibodies or overreaction of immune cells by the attack in the body. Thus, antibodies have developed a method to recognize the protein pattern or overall structure of antigens and destroying them without damaging the normal and healthy cell or their components.

Conclusion

Immunity cells like natural killer cells and cytotoxic T cells recognize cancerous cells by their different surface protein patterns. They recognize these cells as foreign or nonself cells of the body due to unusual protein pattern on them and kill them. In order to elicit an effective immune response, antibodies recognize the overall structure of antigen and bind to the large molecules only as small molecules are not capable of eliciting an immune response.