Major Classes of Protein

Immunoglobulins (Ig) which are also known as the antibodies are molecules made of a glycoprotein produced by the white blood cells. These antibodies are large Y-shaped proteins. They are the essential part of the immune system whereby once an antigen enters the blood system they recognize it and bind to it and help in destroying it. Such antigens are bacteria, cancer cells, fungus, etc. The immune reaction of the antibodies to the antigens is very complex and so specific. For instance, antibodies which respond to flu attach only to the flu virus (specificity). The tip of the Y of the immunoglobulin has a paratope (an antigen-binding site) that attaches to a specific epitope (antigenic determinant) of the specific antigen to which the antibody reacts.

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Through the process of binding the antibody may neutralize the antigen or result in complement fixation whereby, complements attack the antigen. The binding mechanism can reduce the rate at which the biological processes of the antigen that cause the disease, occur or may tag macrophages to react and destroy it. The communication process of the antibody with other constituents of the immune system is enabled by the Fc region which is on the pedestal of the Y protein which has a glycosylation site. This is a site where the enzymatic process of binding glycans to proteins, lipids or many more organic molecules takes place. These glycans in the glycosylation site are essential in the making of the structure of the antibody as well as its functioning. The innumerable immunoglobulin isotypes vary in their biological structures, organization, target specificity and distribution (eBioscience, 2015). These antibodies mainly differ at a small region at the tip of the Y protein. This is the hypervariable region. This enables the various antibodies to bind to different antigens. Due to this, the antibodies in the immune system can identify a huge diversity of the antigens. The antigen tie site is shaped someplace a dense chain variable domain (VH), and a light chain variable domain (VL) come close together (eBioscience, 2015).

The V regions and C regions are the variable and constant parts of the antibody which are found on each arm of the antibody. The variable domains are bound to the continuous domains. As the designation infers, the variable domains contrast in their amino acid arrangement from one antibody fragment to another, giving the vast assortment the immune system desires to fight extraneous invaders (eBioscience, 2015).

The immunoglobulins are in two main forms; the soluble antibodies that are secreted by the B cells into the blood, and the membrane-bound antibodies which consist of the hydrophobic transmembrane region. The membrane-bound antibodies are bound to the surface of the B cell thus the name B-cell receptor.

The immunoglobulins consist of two main structural units which are the heavy chains and the light chains. Each antigen consists of two of each of the chains, that is, two heavy chains and two light chains. The heavy chains are of five types of the mammalian immunoglobulins which are a, d, e, g and m. These chains are found in the antibodies and each heavy chain that is present in the antibody whichever the type; gives the class in which the antibody is found. These chains vary in size and constitution whereby; chain a and g roughly constitute of 450 amino acids and on the other hand m and e have about 550 amino acids. Each chain has the V and C region whereby the C region is the same for each antibody which in the same isotype but varies in the immunoglobulins which are of different isotypes.

The light chains, on the other hand, are l and k in mammals. These chains also constitute of the C and V region. In each antibody, there only exists one type of the light chain which occurs in pairs.

There are five main antibody isotypes which are grouped as to per the variations of the sequences of amino acids in the Fc region of the immunoglobulin heavy chains. These are;

IgA

IgD

IgE

IgG

IgM

The main functions of the antibodies are as follows;

Neutralizing parts of the bacteria or virus thus making it ineffective.

Agglutination whereby the antibodies come together and glue the foreign substances or cells in the body that attract the process of phagocytosis.

Precipitation where the immunoglobulins glue the antigens that are soluble in the blood plasma hence, these antigens precipitate out of the plasma in the form of clumps that attract the process of phagocytosis.

Complement fixation where the immunoglobulin clasped onto the antigens enables the attack of these antigens by the compliments which occur through membrane attack complex.

The statement form follows function in this case is accurate to me. From the description above on how the immunoglobulins are structured and how they function, I believe that the statement is accurate to be form follows function. The immunoglobulins are created to provide immunity. Initially, it is identified that they are to provide immunity, and the way they are structured is to perform their duties efficiently and effectively. Therefore, it is correct to say that form follows function. This statement is neither meaningless nor tautological. One cannot describe the function of an object without describing how it is structured to perform that function. It is the same in this case whereby you cannot describe the functions of the immunoglobulins without mentioning how they are structured to perform these functions.

References

Affymetrix eBioscience. (2015). Immunoglobulin (Ig). Retrieved from http://www.ebioscience.com/knowledge-center/antigen/immunoglobulin/structure.htm