Amino Acids and Proteins, Simple Proteins

Proteins are the most important biological macromolecules occurring in all living cells. They occur in great variety and kinds, ranging in size from relatively small peptide to huge polypeptides with a molecular weight in millions. Proteins are the building blocks of our body/life. They are high molecular mass of complex bio polymers of amino acids. These amino acids linked with each other by a special linkage known as peptide linkages. Relatively simple monomeric subunits amino acids provide the key to the structure of proteins.

What is most remarkable is that cells can produce proteins with striking different properties and activities by joining the same 20 amino acids in many different combinations and sequences. From these building blocks, different organisms can make such widely diverse products as enzymes, hormones, antibodies, milk proteins, muscle proteins, lens proteins, spider web, silk proteins, and number of other substances having distinct biological activities. On the basis of constitution, proteins are classified into,

simple proteins
conjugated proteins.

Simple Proteins

Proteins are the most important biological macromolecules occurring in all living cells. They occur in great variety and kinds, ranging in size from relatively small peptide to huge polypeptides with a molecular weight in millions. These are formed of amino acids only. They include albumin, globulins, histones, actin myosin and keratin. In simple proteins, the amino acids are serially linked by peptide bond ( c NH-) or amide bond formed between amino acids and carboxylic groups of successive amino acids (Fig). The order in which amino acids Occur is specific for particular protein. Albumin, globulins, histones are exam pies of simple proteins. Albumin. Human serum albumin has a molecular weight of 68,500 and it makes up about half of the total serum protein. Serum albumin non covalently binds as many as 10 fatty acids and they are carried to tissues such as skeletal muscle, heart and renal cortex. Here fatty acids dissociate from albumin and are transported into cells to serve as fuel.

Histones Proteins

Histones are small, basic proteins found in the chromatin of all eukaryotic cells. The molecular weight ranges between 11,000 and 21,000. Histones are rich in the amino acids, arginine and lysine. The DNA in the chromatin is very tightly associates with histones and form a structural unit in the DNA called nucleosomes. In prokaryotes, there are no comparable structures to those of eukaryotic nucleosomes. Histone like proteins are abundant in E.col.

Actin and Myosin Proteins

Organisms move, cells move, organdies are macromolecules within cells is move. Most of these movements arise from two protein molecules of muscle. Both actin and myosin are the major proteins. The contractile force of muscle is generated by the interaction of actin and myosin. Together, these two proteins make up 80% of proteins mass of muscle. This is the best example for how proteins translate chemical energy into motion. In muscle cell, in filaments contraction, my fast thin actin contraction, these proteins are arranged (Fig). During muscle contraction, myosin (thick fi1ament)slide Fast thin actin filament to bring about contraction.




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