PROTEINS

proteins  Proteins are polymers composed of sub-units called amino acids that are linked by peptide aminde bond

Amino acid  amino acid are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids.

Amino acid  general formula for α -amino acid is H 2 NCHRCOOH where R is an organic substituent the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (the α –carbon ).

Amino acid: There are two types of amino acids:  non-essential amino acids can be made by the body.  essential amino acids cannot be made by the body and must be got from food. There are 8 essential amino acids.

Amino acid  essential amino acid isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.  histidine is considered semi-essential because the body does not always require dietary sources of it.

Action of proteins: Proteins provide structure in  membranes  Bulid cartilages  Connective tissue  Transport oxygen in blood and muscle  Direct biological reaction as enzyme  Defend the body against infection  Control metabolic process as hormones  Can even be source of energy

albumin Albumin is the main protein of blood plasma; it binds water, cations (such as Ca 2+, Na + and K + ), fatty acids, hormones, bilirubin and drugs  its main function is to regulate the colloidal osmotic pressure of blood.

gelatin  Gelatin is a translucent, colorless, brittle (when dry), tasteless solid substance  derived from the collagen inside animals' skin and bones.  It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing.

Physical properties GelatineAlbumin Vitreous, brittle solidsolidState faint yellowColorelesscolor Almost odorlessCharacteristic odorodor Tasteless Taste Soluble in water, hydrophilic colloid Soluble in waterSolubility

a.Protein solubility All proteins dissove in dilute acid,base and water  Dissolve 0.5 g of protein in  Distilled water  0.9% NaCl  HCl  NaOH  With heat and shake

b.Coagulation and precipitation test  1.precipitation by heat:  Add 5ml of protein solution in a test tube then add 2 drops of diluted acetic acid with shake then heat the above part of the tube  Result:  White turbidity will appear

b.Coagulation and precipitation test  2.precipitation by conc. Acid  Add 2ml of conc. Nitric acid in a test tube then in the wall of the tube add 2ml of protein solution  Result  White ppt will appear

b.Coagulation and precipitation test  3.Precipitation by minerals neutral  1. precipitation by half conc. Salt:  Add to 3ml of ammonium sulfate 3m; of protein solution  Result:  Ppt will appear

b.Coagulation and precipitation test  3.Precipitation by minerals neutral  2.precipitation by conc. salts:  Add to 5ml of protein solution ammonium sulfate crystals with shake  Result:  Ppt will appear

b.Coagulation and precipitation test  4.precipitation by alkaloids  Add to protein solution drops from :  10% tungestic acid  10% trichloracetic acid  Result:  Ppt will appear

b.Coagulation and precipitation test  5.preciptation by alcohol :  Add to 3ml protein solution 6ml of(70-90%) of ethyl alcohol  Result:  Ppt will appear

b.Coagulation and precipitation test

d.Gel formation test: 2  Dissolve 0.5 g of gelatin in 10ml hot H 2 O in test tube then cool the test tube in ice bath  Result:  Gel will formed

Chemical tests

Chemical tests:  General test for all protein  Biuret test:  Add 3ml of protein solution, 3ml of 10% NaOH with shake, then add 2 drops of 1% CuSO4 after shake violet color will appear

Chemical tests:

Chemical tests  Differentiation test:  Millon test:  Add to 2ml of protein solution 3drops of millon’s reagent white ppt will appear  Result:  +ve albumin  _ve gelatin  Then heat the test tube transfer to red ppt with (albumin and gelatin)

Chemical tests

Chemical tests:  Differentiation test:  Lead acetate test :  Add to 0.5 ml of protein solution 0.5ml of 20% NaOH heat the test tube in water bath for 1 min. then add 2 drops of conc.lead acetate  Result:  Brown color(+ve) with albumin “gray ppt.”  -ve with gelatin

Chemical tests:

Last lab Good lack for my first group