PROTEINS
PROTEINS
Proteins are a class of most important compounds that are found in living organisms. Proteins are the main constituents of our body such as muscles, skin, hair and nails. Protein carry all vital life processes
in the human system. Proteins are built up of a large no of alpha amino acid molecules inter linked by peptide bond. In this way very long chains of amino acids are built up from 200 to 60,000 amino acid units of relative molecular mass from to 17,500 to 6000,000 . In general it ranges from 34000 Daltons to 50,000,000 Daltons. Proteins are a vast class of substances of almost unbelievable diversity in structure and function. When proteins are hydrolyzed with dilute acids, a mixture of alpha amino acids is obtained.
CLASSIFICATION OF PROTEINS
Proteins ate divided into three main classes :
1. Simple protons
2. Conjugated proteins
3. Derived proteins
SIMPLE PROTEINS
The simple proteins are those which are made of amino acid units only, joined by peptide bond. Upon hydrolysis they yield mixture of amino acids and nothing else.
Examples:
ALBUMINS : Egg albumin, serum albumin , Lact albumin
GLOBULIN : Tissue globulin, serum globulin
GLIADINS : wheat gliadin, hordein ( barley) etc.
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CONJUGATED PROTEINS
Conjugated proteins are composed of simple proteins combined with a non-proteinous substance. The non-proteinous substance is called prosthetic group or cofactor.
Examples:
chromo-proteins:
haemoglobin in which prosthetic group is iron
phospho-proteins:
casein in milk: in which prosthetic group is phosphoric acid
DERIVED PROTEINS
These are not naturally occurring proteins and are obtained from simple proteins by the action of enzymes and chemical agents.
Examples: peptones, peptides , proteoses etc.
FUNCTIONS OF PROTEINS
Proteins are structural materials of animal body and help in the growth of animal body. Proteins are also involved in nervous defence, metabolic regulation, biochemical catalyst and oxygen support. They build new tissues and maintain already present tissues.
SOURCES OF PROTEINS
Meat (all types) , milk, eggs, pulses, beans, peas, lentil, seeds, nuts, oil containing fruit etc.
CALORIFIC VALUE
OF PROTEINS
One gram protein provides 4 calories of energy
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