Proteins

Proteins are among the most essential biochemical molecules in life. They are the main molecules that form basis for both human and animal tissue structural components. This is because they play a vital role in building, maintaining and replacement of tissues in the body. Moreover, they are also responsible for transportation of ions and molecules across hormones and membranes in the body.

Proteins can be described generally as natural polymer molecules that consist of amino acid units. Amino acids refer to chains that are covalently bonded through peptide bonds. The number of amino acids in a specific protein varies from two to thousands. There are 22 types of amino acids known, thus, the variations in proteins occur due to the infinite number of possible combinations of these 22 amino acids in the formation of polypeptides or proteins.

There are usually four levels of protein structure. These levels of protein structure include the primary, secondary, tertiary and quaternary structures. Primary structure refers to the linear sequence or arrangement of amino acids in a protein or polypeptide. This structure is important since for proteins and peptides to work properly they must have correct amino acids sequence, failure to which may lead to deficiencies such as sickle cell anemia. These amino acids as they bond to form proteins they tend to bend and coil. The secondary structure of a protein refers to this bending and coiling of the polypeptides. The most common forms of secondary structure that either can exist independently or jointly are the beta pleated sheet or alpha helix (Whitford 2005).

The tertiary structure of a protein ensures the stability of a protein. This structure refers to the folding of protein molecules upon themselves attached together through hydrogen bonds hydrophobic forces, ionic bonds or salt bridges, covalent links, and disulfide bridges. Finally, the quaternary structure refers to the complex structures formed when two or more polypeptide chains combine. A good example of a protein with quaternary structure is the hemoglobin, consisting of two alpha chains of 141 amino acid residues and two beta chains of 146 amino acid residues.

An antigen is a substance that leads to immune response when it is introduced into the body of an organism and has the capacity of binding with the particular antibodies. Hydrogen bonds, van der Waals forces, and ionic forces between antibody and antigen facilitate this binding. In the antibody antigen interaction, the antibody is a Y-shaped protein known as immunoglobulin. The antibodies are secreted and produced by B cells. The structure of protein is very helpful in this interaction as it assists the antibodies continually change their tips form. This variable state of the tips – hypervariable region of the antibody is vital because it brings existence of antibodies with slightly diverse tip structures, or antigen binding sites. Furthermore, the protein structure is important as it facilitates the random combination and mutations of antibodies that allows the immune system to fight varied antigens.

In conclusion, proteins are vital components that are essential for life. Their structure is also essential as it facilitates functions such as the enzyme – substrate interactions and the ability of a hormone to control only one particular type of cell in the body. Consequently, lack of or insufficient protein in the body may lead to deficiencies such as kwashiorkor and body wastage.

 

References

Whitford, D. (2005). Proteins: structure and function. New York: John Wiley & Sons.

 

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