Quaternary structure are formed when a charged of a molecule with polar covalent bonds forms an electrostatic interaction with a substance of the opposite charge. The folded parts within the structure are holded by Van der Waal’s forces. The sulphur bridges are formed between two cysteine side chain that end up next to each other due to folded peptide chain. Lysine is an example of a protein that uses ionic bond. Ionic bonds are very strong intramolecular forces. Lysine is use in the treatment of herpes and also increase the absorption of calcium in our body.Threonine includes hydrogen bonding and play an important role in fat metabolism. It prevents the accumulation of fat in the liver and is very useful with indigestion and intestinal disorder.Methionine is is highly hydrophobic protein with sulphur bonded amino acid.  Its play in essential role in prevention of deposition of fat in the liver and, also have fat dissolving effect in the body.https://www.google.co.uk/search?q=protein+4+levels+of+structure=active=lnms=isch=X=0ahUKEwj8nMrV3rvXAhWEKewKHUiTDDIQ_AUICigB=1920=974=1#imgrc=6LvXIVzVziGsbM:Nucleic acidNucleic acids are large biomolecules that are essential to all known forms of life. They allow organisms to transfer genetic informations from one generation to the next. Nucleic acids are composed of nucleotide monomers linked together. Nucleotides are made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. There are two type of nucleic acids; ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). Polynucleotide chains are formed when nucleotides are linked together by covalent bonds between the phosphate of one and the sugar of another. These linkages form the sugar phosphate backbone of both RNA and DNA and are known as phosphodiester linkages. The nucleotide structure is shown below;A polynucleotide is composed of 13 or more nucleotides monomers covalently bonded in a chain. The covalent bonds are between the phosphate group of one nucleotide and the third carbon atom of the pentose sugar in the other nucleotide.DNA and RNA are structurally nearly identical. There are three differences in the structure of RNA which makes their function very different from that of DNA. The three differences are: RNA has ribose sugar instead of deoxyribose sugar like in DNA. RNA has uracil instead of thymine.DNA is double stranded whereas RNA is mostly single stranded. The two strands of DNA are coiled together to form a double helix. There are cross-links between the complementary base pairs. importance of nucleic acids:Nucleic acids store information that is used for proteins. The DNA stores genetic information that is needed by the cells to function and RNA is used to convert the information from DNA into proteins. Proteins are used to make hormones, enzymes and other body chemicals. It is a building block for cartilage, bones, skin, blood and muscles. Role of enzyme in metabolism:Each enzyme only promote one type of reaction. Some enzymes break down large nutrient molecules into smaller molecules. They break down nutrients such as fats, proteins, carbohydrates during digestion in the stomach. Other enzymes guide these smaller molecules through the intestinal wall into the bloodstream. There are some enzymes that promote the formation of large molecules from the smaller ones. Enzymes are also responsible for some other functions in the body such as, release and storage of energy, the process of respiration, the course of reproduction.Antibody:An antibody also known as immunoglobin is a Y-shaped protein that is produced by plasma cells. These plasma cells are used by the immune system. The antibody recognizes an antigen which is a unique molecule of the pathogen. Hormones;Hormones are chemical secreted by the glands to help regulate the processes in the body. They are targeted for different organs. The hormones are transported from the gland to the targeted organ through the bloodstream.