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The main functional groups of an amino acid.
Types of amino acids.
Different amino acids are different in their “R” groups.
Amino acids are amphoteric.
Amino acids are amphoteric.
Amino acids can be a “buffer”. It reduces the pH change
in its solution.
Electron sharing between two amino acids can cause
changes in their ionic structures.
The condensation in the formation of peptide bond.
The formation of the dipeptide is by the condensation
of two amino acids (by removing 1 molecule of water).
The formation of the peptide bond.
The hydrolysis and condensation of peptide bonds.
The sequence of amino acids along
The peptide chain is called the
Primary structure.
The secondary structure of the peptide chain
Is the natural shape of the chain
Caused by the tetrahedral chemical bonds.
One form of the secondary structure of the peptide chain
Is called -helix.
the structure of the -helical polypeptide chain.
Another form of the secondary structure is called
the -pleated sheet.
Another form of the secondary structure, the -pleated sheet.
The tertiary structure of the polypeptide chain
Describes the bending and folding of the
Helical structure.
Electrostatic attractive force (ionic bond),
Covalent bond, disulphide bond,
And the Van der Waal force contribute
To these foldings.
Formation of the disulphide linkage between
2 sulphur containing amino acids.
Hydrogen bonds within the polypeptide chain would
holding the bending of the amino acid backbone.
Disulphide bond
Disulphide bond is a covalent bond, which hold the folding
of the amino acid backbone permanently.
The maintenance of the tertiary structure of the protein.
The peptide chains can be inter-linked
with cross-bridges, the disulphide bonds.
The tertiary structure of a protein, lysozyme.
The tertiary structure of a protein, myoglobin.
The quaternary structure describes the association among the
polypeptide chains and the non-proteinous groups.
The conformation of the protein is very important.
If the conformation is changed, the property of
the protein will also be changed.
For example,
if the the haemagglutinine of the current H5N1 virus
has one amino acid changed,
its conformation would be changed.
The conformation may become much easier
to combine with the receptor protein on the
surface of the human cells.
Then, human would become susceptible to the
infection of the virus.
If the conformation of the normal prion protein in beef
is changed, it would affect other prion proteins to become
bad and caused the mad cow’s disease.
A dipeptide can be hydolysed into 2 amino acids.
Specific protein enzyme would break the amino acid
backbone at specific point.
The action of the enzyme, chymotrypsin can break the bond
between the amino acids phenylalanine and alanine.
The factors that can make proteins
work properly.
Proteins need water to behave properly.
If there is no water, hydrogen bonds cannot
be established.
The protein molecule cannot extend to its
natural shape.
Then, the protein cannot work.
Proper acidity (pH)of the solution
If the pH of the solution is not suitable,
there will be too much or too few
hydrogen bonds.
The molecule cannot extend property,
it cannot work.
Proper temperature :
If the temperature is too high,
the disulphide bonds would be broken.
The protein molecule would be distorted
(or even coagulated), then, it will stop
working.
Presence of co-factors :
Some proteins need some special material
to help its work.
They are called co-factors.
If the corresponding co-factor does not exist,
the protein cannot work.