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 changein its solution.

Electron sharing between two amino acids can causechanges in their ionic structures.

The condensation in the formation of peptide bond.

The formation of the dipeptide is by the condensationof 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 alongThe peptide chain is called the Primary structure.

The secondary structure of the peptide chainIs the natural shape of the chainCaused by the tetrahedral chemical bonds.

One form of the secondary structure of the peptide chainIs called -helix.

the structure of the -helical polypeptide chain.

Another form of the secondary structure is calledthe -pleated sheet.

Another form of the secondary structure, the -pleated sheet.

The tertiary structure of the polypeptide chainDescribes the bending and folding of the Helical structure.

Electrostatic attractive force (ionic bond),Covalent bond, disulphide bond,And the Van der Waal force contributeTo these foldings.

Formation of the disulphide linkage between 2 sulphur containing amino acids.

Hydrogen bonds within the polypeptide chain wouldholding 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-linkedwith 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 thepolypeptide 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 virushas one amino acid changed,its conformation would be changed.

The conformation may become much easierto combine with the receptor protein on the surface of the human cells.

Then, human would become susceptible to theinfection of the virus.

If the conformation of the normal prion protein in beefis changed, it would affect other prion proteins to becomebad and caused the mad cow’s disease.

A dipeptide can be hydolysed into 2 amino acids.

Specific protein enzyme would break the amino acidbackbone at specific point.

The action of the enzyme, chymotrypsin can break the bondbetween 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 cannotbe established.The protein molecule cannot extend to itsnatural 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 stopworking.

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.