Protein Proteins are organic compounds containing carbon, hydrogen, oxygen and nitrogen. It may contain sulphur and phosphorous also. Amino acid is the simplest unit of protein. The quality of protein depends upon the amino acids they contain. There are about 20 amino acids which are essential for human growth and development. Human body cannot synthesize these amino acids. There fore, these amino acids must be present in the proteins we eat.

Proteins are the most body building –materials. They are essential for growth, repair and replacement of injured parts.

Structure of protein A protein exhibits four levels of structural organization: 1.Primary Structure of Proteins: To define, primary structure of a protein is the sequence of amino acids that are linked by covalent peptide bonds to form a polypeptide chain. It is the description of basic structure of a protein. 2.secondary Structure of Proteins: It is the repeated twisting and folding of neighboring amino acids in the polypeptide chain The secondary structure is stabilized by hydrogen bonds which form at regular intervals along the polypeptide backbone.

3.TertiaryStructure of Proteins: The tertiary structure of a protein refers to its three-dimensional shape of a polypeptide chain. Each protein has a unique tertiary structure that determines how it will function. 4.Quaternary Structure of Proteins: When a protein contains more than one polypeptide chain, the arrangement of individual polypeptide chains relative to one another is Quaternary structure.

Diagram of Protein structure

Sources of protein Good Sources Fair sources Poor sources peas (200 g)16.0gBrown rice (200g )4.4g1 Carrot0.4g soya beans( 225 g)11.5gBroccoli (100g )3.1g1 Apple0.3g Cow's milk ½ pint9.2gPorridge [water] (160g )2.4gCream, double (20g ) 0.3g Meat and fish15-26 g- Egg, boiled7.5gPotatoes (200g )2.8g Peanuts (30g )7.3g Bread, (2 slices)7.0g Hard cheese (30g )6.8g

Functions of Protein Some of the functions of proteins are given below. 1.Many proteins act as catalysts, thus enhancing the rate of chemical reactions to such extents as needed by the living cells. 2.The fibrous proteins serve as components of the tissue holding the skeletal elements together. 3.Proteins are essential components of cytoplasm and therefore, very essential for growth.

4.Proteins are essential for the repair of worn-out tissues. 5.In case of deficiency of carbohydrates and fats, proteins are utilized for energy. 6.The muscles of body are formed from the proteins. 7. Protein acts as enzymes, co-enzymes and hormone and control various body activities.

Protein Deficiency Causes: 1.When the diet contains sufficient energy but not enough protein. 2.Lack of sufficient energy in the diet. In this situation the body’s own protein is used as a source of energy.

Deficiency diseases I.Kwashiorkor In both types of protein deficiency kwashiorkor develops. It is a disease of the child removed from the breast by the birth of the next one, switching the child from a milk diet to a starchy diet.

Signs and symptoms: 1.Pot belly(swollen stomach) 2.Thin legs 3.Ugly patches on skin 4.Mental retardation 5.Slow physical growth. 6.Reduced resistance to infection

II. Marasmus Due to a lack of energy in diet Symptoms 1.Loose folds of skin 2.Very thin arms and legs 3.Slow growth of body 4.Child becomes lethargic 5.Very under weight.

Sources Retrieved on 6 th of September, 2010 from Retrieved on 6 th of September, 2010 from to be confused with Marasmius. Taylor,D.J., Green,N.P.O.,&Stout,G.W.(1997). Biological science 1&2.United Kingdom: Cambridge University Press.