We must have played the building blocks game or stringing beads into a necklace. In both of these games, small units are attached to form a complete unit. Or we can say that in both of these games, small units are jointed together in a certain pattern to construct form a large object. Similarly macromolecules are molecules which consist of many small molecules. These small units are called as monomer units which are bonded with each other in a certain manner to form macromolecules.
Macromolecules are very big molecules which are composed of more than one atom. The number of monomer units can be 10,000 or more. Macromolecules are also called as polymer. Here poly- stands for 'many'. Similarly monomer units are basic units of any macromolecules. Here mono- term stands for one unit. So macromolecules can be defined as the molecules which are formed by small basic units which are called as monomer units. The process of formation of macromolecules from the combination of monomer units are called as polymerization. There are many examples of macromolecules such as polythene, PVC etc.
Many of the macromolecules are involved in different biological processes such as proteins, carbohydrates, nucleic acid etc. Synthetic macromolecules like common plastics and synthetic fibres can be synthesized in artificially. In living organisms, four major macromolecules are involved in biochemical reactions. These macromolecules are also called as biomolecules and they are carbohydrates, nucleic acids, proteins and lipids.
We can observe many of the macromolecules in our everyday life. We are using different objects made from plastic. Plastics are macromolecules
of different organic and inorganic compounds. Similarly the clothes which we wear are made from either cotton or some synthetic fibers. These synthetic fibers are basically macromolecules like polyester, terylon etc. Other synthetic fibers are nylon-6, nylon-6, 6 etc. Apart from theses macromolecules many biological molecules are macromolecules only and consist of some monomer units. Here monomer units are linked together with ionic bond, additional reaction or condensation process. Some other type of bonding between monomer units are disulphide linkage, Vander wall linkage, hydrogen bonds etc.
Let’s take a simple example of macromolecule. Proteins are macromolecules
which play an important role in biological activities. Protein molecules are composed of small monomer units which are called as amino acids. Amino acids are molecules with tow opposite functional groups; carboxyl group and amino group. These two functional groups involve in condensation reaction and link with each other to form macromolecule. Since each bonding furnish with elimination of water molecule therefore such macromolecules are known as condensation polymers. Another example of macromolecule is polythene. Unlike proteins, polythene is a synthetic macromolecule. It consists of ethene molecules as monomer units. It is an additional macromolecule as it is formed by the additional reaction of ethene molecules.
The macromolecules which involve in biochemical reactions are also known as biomolecules. Biomolecules are macromolecules as they composed of different monomer units and they are bulky in their size. Vitamins, hormones, enzymes, ATP, carbohydrate, protein, lipid, nucleic acid are good examples of biomolecules which are mainly found in living cells. The monomer unit of carbohydrate is monosaccharides which are basically polyhydroxy aldehydes or ketones. They are linked with each other through glycosidic linkage.
Another macromolecule is nucleic acid which is composed of nucleotide units. They are mainly responsible for the transfer of genes or characters from one generation to another. Proteins are building blocks of living organisms. They are made of amino acids which are bonded through condensation reactions. Monomer units of a macromolecule are arranged in three-dimensional structure and provide several levels of organization.
Examples of Macromolecules in Carbohydrates
Back to Top
Like other biomolecules; carbohydrates are also macromolecules
which are composed of certain monomer units. The monomer units of carbohydrates are called as monosaccharides which polymerize to yield polysaccharides. For example; glucose is a monosaccharide and polyhydrxy aldehyde. It has a carbonyl group; an aldehyde with hydroxyl groups on the other carbons. The ring structure of glucose is known as internal hemiacetal.
Monosaccharide units are polymerized with the elimination of the elements of water. Thee condensation step occurs between the anomeric hydroxyl and a hydroxyl of another sugar. This bond between two monomer units is known as glycosidic bond. If the formation of glycosidic linkage removes carbonyl group from the macromolecule, such molecules are non-reducing in nature such as sucrose. On the contrary, if the anomeric hydroxyl forms glycosidic linkage with a non-anomeric hydroxyl of another sugar, than there will be a reducing end with a free anomeric carbon; hence such macromolecules
will be reducing sugars such as maltose.
Proteins are also called as polypeptide. This is because many peptide units are linked together to form proteins. Peptide units are formed by the combination of many amino acid units which are bonded with each other through peptide linkage. Amino acids have two functional groups mainly; a carboxylic acid (-COOH) group and an amino (-NH2) group. Here amino groups are usually attached to the carbons which are alpha to the carboxyl carbons therefore they are also called as alpha-amino acids. Except glycine, all other amino acids are optically active due to presence of chiral carbon atom. The combination of amino acids is a condensastion reaction which occurs with the elimination of water molecule. Since this is a bond between carboxyl group and amino group which forms an amide linkage therefore it is called as peptide linkage. The sequence of monomer units in protein molecule is called as primary structure.
Lipid is another example of macromolecule which involves in different biological activities. Lipids exhibit great structural varieties and named differently such as fatty acids, soaps and detergents, fats and oils, waxes.
phospholipids, eicosonoids, terpenes, steroids, lipid soluble vitamins etc. Fatty acids are long chain carboxylic acids which can be saturated or unsaturated in nature. Some common examples of fatty acids are given below.
|| Common Name
|| Palmitoleic acid
|| Oleic acid
|| Linoleic acid
|| Linolenic acid
|| Arachidonic acid