1. Protein

Protein are polymer of amino acid.

Protein have one amino group and one carboxylic acid.

Protein are three dimensional structure.

Protein involves peptide bond.

RNA translation protein is form.

1. Alpha carbon are bonded by four group are
2. R group
3. Amino group
4. Carboxyl group
5. Hydrogen.
   

Protein of structure divided into four levels of organisation.

1. Primary structure
2.  secondary structure
3.  tertiary structure 
4. quaternary structure

Primary structure

primary structure of protein refers to the sequence of amino amino acid in the polypeptide chain .

Primary structure is held together by covalent bonds and such as peptide bonds which are made during the process of protein biosynthesis or translation.

 two ends polypeptide chain referred to as carboxyl terminals and amino terminus based on the nature of free group.

Secondary structure

polypeptide by twisting for folding is referred to as secondary structure.

 amino acids located close to each other in their sequence most common type of secondary structure are.

1. the Alpha helix and
2. beta pleated sheet.

Alpha helix and beta plated sheet pattern are stabilized by hydrogen bond between carboxyl and amino group in the polypeptide backbone.

Alpha helix

Alpha helical structure was proposed by pauling and Corey 1951.

Alpha helix  of shape is spiral, rigida rod like structure that forms when polypeptide chain twist into helical form.

Alpha helix is stabilized by hydrogen bond in between amino group and carboxyl group.

All peptide bond, except first and last last in polypeptide chain participate In hydrogen bonding.

Alpha helix is right handed or left handed.

Beta pleated sheets

Propose by pauling and Corey.

Beta pleated sheets form when two or more polypeptide chain segment line up  side by side.

beta platelets are stable by hydrogen bond that formed between polypeptide backbone amino group and carboxyl group adjacent stand is either  parallel or antiparallel.

the polypeptide chain are arranged in the same direction.

Tertiary structure

Three dimensional structure of protein

Compact structure with hydrophobic side chain held interior while the hydrophilic group are on the surface of protein molecules.

Following type of bond in tertiary protein structure.

1. hydrophobic interaction
2.  electrostatic interaction 
3. hydrogen bond 
4. Vander waal force 
5. covalent bonds.
   

quaternary structure

Protein are composed of two or more polypeptide chain .

Protein are catalytic active.

polypeptide subunit  are held together by non-covalent interactions such as hydrophobic interaction, Ionic  bond and hydrogen bonds.

Subunit in multisubunit protein may be identical or quite different.

 multisubunit protein in which some or all subunit are identical are referred to as oligomer and identical unit are referred to as protomers.