A primary structure
is the distinctive sequence of amino acids which make up a protein. This
sequence is also known as a polypeptide chain.
To make it less complicated and abbreviate each amino acid residue with
either a three letter or one. The protein chain in the primary structure depends
all on the identification of the amino acid sequence. These molecules determine
how the molecular chain will fold.
The polypeptide bonds are created by enzyme catalysed
condensationreactions. Then it is broken by the enzyme catalysed hydrolysis
reactions. The monomers in the diagram below show that they form proteins. Proteins are made up of a variation of amino acid
polymers, and they are different type of bio-molecule in our bodies.Different
protein types include enzymes that catalyse chemical reactions receptors that
control signalling in bodies. Haemoglobin carried oxygen throughout the bloodstream,
muscle and organ tissue, which gives your body structure and mobility, and so
many other things.
Amino acids form peptide bonds with one another, the
peptide bond between the two–NH and CO units, cause a condensation reaction.
This is called a carboxyl group. Every amino acid has
reaction is the reaction of two small molecules that make a larger molecule
– e.g. H2O
In this process water is removed.
is a long polypeptide chain of amino acids. Amino acids are attached together
via the peptide bonds. Then they make chains of amino acid chain.
Once the primary structure of the
polypeptide is formed, it begins to twist into regular patterns that make up
the secondary structure. The primary structure just describes the linear sequence of
amino acids, and it is dictated by the peptide bond that links to each amino
acid. This is a simple linear structure. You take an amino acid and bond them
together and that bond is called a peptide bond, very strong covalent bonds. Secondary
structure forms as hydrogen bonds form between backbone atoms. The tertiary
structure is the final fold of the protein and that is held by hydrogen, ionic
and disulfide bonds. The proteins which have more than one polypeptide chain is
a quaternary structure and that is represented by three dimensional arrangement.
Beta pleated sheet and ?loop.
These twists are formed
of as a regular pattern of hydrogen bonds between NH and C=O groups on thee
polypeptide chain. The beta sheet are formed by hydrogen bonds and there structure is
In secondary structure there are
hydrogen bonds forming between the peptide groups. In the secondary structure the major
bond is the hydrogen bond apart from the peptide bond and disulphate bond. In
secondary structure the structure is referred to the plated sheet that a
proteinchain can form because of hydrogen bonding. When the process is finished
that whole shape of the polypeptide is refereed as tertiary structure- So after
the polypeptide chains form they are now called proteins. This happens in
the r groups of amino acids in the chain.
Each amino acid has a central atom with an
amino acid group and a carboxyl group and a hydrogen atom. When a water
molecule is occurred during a reaction between NH2 of on amino acid and –COOH
of another amino acid this is when the
peptide bond is formed.
Disulphide bond occurs only in
certain amino and specific group which is referred as a sulfhydryl group.
When the SH groups of two cysteine residues
are covalently linked as a dithiol by oxidation that is when disulphide bonds
Hydrogen bond is a bond between a
hydrogen atom and an electronegative atom like oxygen, nitrogen. In amino acids
the electromagnetic attract interactions between polar molecules. So the bond
is weak when hydrogen is stuck to a highlyelectronegative atom, like N or O.
there are hydrophobic bonds, hydrogen bonds, ionic bonds, Van der Walls forces,
Di-sulphite bonds. As amino acids interact the protein may fold upon itself.
In the Quaternary
structure there are hydrophobic bonds, hydrogen bonds, ionic bonds, Van der
walls forced an di-sulphite bonds.
Ionic bond is a bond
between oppositely charged amino acids of an aspartic acid which is a base
acidic amino acid it is a negatively charged where as lysine is a positively
charged amino acid. Van der walls force is a weak electrical force between
atoms. Also it is the sum total of all non covalentbonds between electrically
equal molecules. They hold molecules together.
These blue molecules in the
figure are hydrophilic regions and the red ones are the hydrophobic regions.
The hydrophobic is also referred as water-hating amino acids.
Hydrophobic interactions actually
the bond between two no polar groups. The structure of the side chain can closely associate and are
protected from interaction with solvent water.
So each type of a protein has a three-dimensional
structure; this shows the order of the amino acids in its chain.
A protein can be unfolded or denatured by exploring
with certain solvents, which causes disturbance to the no covalent interactions
that hold the folded chain together. This causes the protein to transfer into a
flexible polypeptide chain which loses its original shape. When the denaturing
solvent is removed, the protein often refolds automatically.