MINISTRY OF DEFENCE

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  MINISTRY OF DEFENCE. Establishment Of National University In Islamabad Total position. 29 Domicile , All over Pakistan    Qualification  intermediate to bachelor positions . Project Engineer(Civil) account Officer  supervisor assistant office boy     How to apply.   Apply online through the link https://www.fgei-cg.gov.pk/nup-rec.php   Last date to apply  02 April 2023. No TA/DA Fo Interview 
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Structure Of Protein

STRUCTURE  OF PROTEIN
Proteins are  polymers of L - amino acids . The structure of protein is rather complex which can be divided 4 levels of organization .
 
1) PRIMARY STRUCTURE 
2) SECONDARY STRUCTURE 
3) TERTIARY STRUCTURE 
4) QUATENARY STRUCTURE

1) PRIMARY STRUCTURE 
 The linear sequence  of amino acids forming the backbone of  proteins   polypeptides .
Peptide bonds 
The amino acids held together  in a protein by covalent peptide  bonds or linkages .
Formation of the peptide bonds 
When the amino group of an amino acid combines with the carboxyl group of  another amino acid a peptide bond is formed  the dipeptides formed two amino acids combined

2) SECONDARY STRUCTURE 
The spatial arrangement  of protein  by twisting  of the  polypeptide chain .
The polypeptide chain by twisting or folding is refered to as secondary structure.
There are two types of secondary structure 
1) ALPHA HELIX   
2) BETA PLEATED SHEETS 

1) Alpha - helix is most common spiral structure of protein .
The alpha helix is stabilized by extensive hydrogen bonding it is formed between hydrogen atoms H attached to peptide N and O atom attached to peptide C . the hydrogen bonds  are individually weak but collectively they are stong and stabilize the helix.
2)BETA PLEATED SHEETS .
In the beta sheets the hydrogen bonds  are formed between the neighbouring  segments of polypeptide chains .
3) TERTIARY STRUCTURE 
The  three dimentional structure  of the functional protein .
The three  dimensional arrangement  of protein structure is refered to as tertiary structure .It is a compact structure with hydrophobic side chains held interior while the hydrophobic groups .
BONDS OF TERTIARY STRUCTURE 
Besides the hydrogen bonds ,disulphide bonds (s-s) ionic interactions electrostatic bonds hydro ophobic interactions and vander walls forces  also contribute the tertiary structure of protein .

4) QUATENARY STRUCTURE 
Some of the proteins are composed of two or more polypeptide chains refered to as subunits  is known as Quatenary structure .
The monomeric subunits are held together by non covalent bonds namely hydrogrn bonds hydrophobic interactions and ionic bonds .

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