Importance and Chemical structure of living organism’s bodies ( Proteins )


They are biological macromolecules ( polymers ) made up of many smaller molecules ( monomers ) called amino acids , Proteins  have high molecular weight and they made up of structural units which are amino acids .

Amino acids

Amino acid is the building ( structural ) unit of the protein , It consists of a carbon atom attached to :

Two functional groups , which are a basic amino group ( NH2 ) and an acidic carboxyl group ( COOH ) .

A terminal group ( R ) , which differs from an amino acid to another .

Hydrogen atom ( H ) .

Amino acids are organic compounds made up of ( H , O , C , N ) atoms and they represent the proteins building units .



Amino acid and building of protein

Proteins are made up of repeated units of amino acids which link with each other by peptide bonds .

The peptide bonds originates between the carboxyl group of an amino acid and an amino group of another amino acid , with the removal of water molecule ( OH group from the carboxyl group of an amino acid and H+ ion from its neighbour amino acid ) .

The combination of two amino acids produces a dipeptide compound , The combination of several amino acids produces a polypeptide chain ( the protein ) .

It is not conditional for the combination to occur among similar amino acids , So , there are extensively wide and various possibilities to form proteins depending on the types of amino acids in the chain , The order of amino acids in the chain and the number of amino acids in the chain .

Amino acid  → Dipeptide compound → Polypeptide chain ( protein ) 

Amino acid  →  Monomer → 2 linked amino acids → Polymer ( 20 linked amino acids )

Glycine is the lonely amino acid that does not contain group ( R ) where it is replaced by a hydrogen atom .

Classification of proteins

Proteins are classified according to the substance involved in their structure into Simple proteins and conjugated proteins .

Simple proteins

They are formed of amino acids only such as Albumin protein which presents in the leaves and roots of plants and the human blood plasma .

Albumin protein prevents the leakage of fluids from the blood vessels into the tissues , So , it maintains osmotic pressure inside the cells , Therefore , its lack in the body leads to occurrence of disorder in osmotic pressure of the cell and makes the body keeps large amounts of fluids that cause a swelling especially in the feet and face .

Conjugated proteins

They are made up of amino acids associated with other elements such as phosphorus , iodine , iron and others .


Amino acids + Nucleic acids , Nucleic protein associated with nucleic acid as ( chromatin inside the nucleus ) .

Amino acids + Phosphorus , Phosphoprotein as casein ( milk protein ) that contains phosphorus .

Amino acids + Iodine , Thyroid gland protein as ( thyroxine ) that contains iodine , It is secreted from thyroid gland .

Amino acid + Iron , Blood Haemoglobin protein ( inside red blood cells ) that contains iron and it is necessary for transporting the oxygen during the respiration process .

Biuret’s reagent is used in detecting proteins in urine .

Importance of proteins

Proteins are involved in the structure and functions of living cells , where :

They are one of the basic components of the cell membranes and chromosomes .

They form the muscles , ligaments , tendons , organs , glands , nails , hair and skin .

They are involved in the structure of many body fluids such blood and lymph .

They are necessary for body growth .

They are involved in the structure of enzymes and several hormones that stimulate and organize all vital processes in the body .

You notice that spider’s net , hooves and hornes of animals are basically made up of proteins .

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