Proteins are very large complex molecules (macromolecules) that have a specific function and sometimes even more than one function. They play a very important role in all aspects of cell structure and function. Although they are complex, they have a simple underlying structure that does not form branches or circles. This is the reason why they are referred to as linear polymers. The simple units that make up proteins are known as amino acids and most organisms have about 20 different kinds. These 20 naturally occurring amino acids are grouped according to criteria such as hydrophobicity, size, aromaticity or charge. They include Glycine (Gly / G), Alanine (Ala / A), Valine (Val / V), Phenylalanine (Phe / F), Proline ( Pro / P), Isoleucine (Ile / I), Leucine (Leu / L), Methionine (Met / M), Aspartic acid / Aspartate (Asp / D), Glutamic acid / Glutamate (Glu / E), Lysine (Lys / K), Arginine (Arg / R), Serine (Ser / S), Threonine (Thr / T),Tyrosine (Tyr / Y), Histidine (His / H), Cysteine (Cys / C), Asparagine (Asn / N), Glutamine (Glu / Q) and Tryptophan (Trp / W). As shown above, they are commonly identified by their three letter abbreviations or one letter symbol. A typical protein, however, is a string of several hundred amino acids. The term amino acid refers to any molecule containing both an amino group and any type of acid group. Thus all amino acids (*except Proline) contain similar structural features such as the amino group, carboxyl group and an alpha carbon. The arrangement in which the amino acids make up a protein chain is known as a protein sequence. The amino acids within these chains are linked by amide bonds and the chains are referred to as peptide chains. These sequences are flexible and determine the characteristic and functional capabilities of the protein.
Proteins perform specific activities in different forms in our body such as enzymes, hormones, antibodies, haemoglobin (blood) and growth and maintenance proteins. Collagen is the most prevalent protein in human beings. It forms strong sheets that support skin, internal organs and tendons as well as the hard substance that gives shape to the nose and ears. It is one of the largest proteins in the body but it is made up mostly of the same three amino acids that keep repeating over and over again. Proteins can be classified by their functions; structural proteins, enzymatic proteins, transport proteins, contractile proteins, protective proteins, hormonal proteins and toxins. However, sometimes different proteins form stable complexes that work together as a group to perform a specific function. Various techniques have been invented to study the structure and functions of proteins and these include mass spectrometry, nuclear magnetic resonance among others. This is normally done in a modern laboratory. The study of proteins is one of the most important branches of science and there is no clear division between the organic chemistry of proteins and their biochemistry
admin January 16th, 2014
Posted In: Handbook