We all have varieties of food items, right?. It includes biryanis, naan, pulao, french fries, burgers etc. You know that these food items contain fibres, proteins, lipids, carbohydrates, nucleic acids etc.
It provides us with the energy we require to perform life processes. So can you tell me what you call these substances? Yes, macromolecules. So the food we have contains macromolecules and micromolecules. In this article we are going to discuss in depth about macromolecules.
Macromolecules are large sized, complex chemicals that have higher molecular weight, that means usually 10,000 daltons and above with lower solubility. Common examples include proteins, carbohydrates, lipids, and nucleic acids.
They are formed by the polymerisation of smaller subunits known as monomers and play a major role in the proper functioning of an organism. They possess chains with various lengths. For example, the monosaccharides are linked with glycosidic bonds in a polysaccharide.
There are mainly four types of macromolecules present in the body of an organism and they are as follows:
The word carbohydrates is derived from the French word ‘hydrate de carbone’ meaning hydrates of carbon. They are represented as Cn(H2O)n. These are macromolecules formed of carbon, hydrogen, and oxygen. These are found in milk, fruits, vegetables, and sugars. Chemically they are polyhydroxy aldehydes or ketones. They constitute a major part of the human diet. Carbohydrates are divided into three types as follows:
They are simple monomers of carbohydrates and have the general formula CnH2nOn. They have only 3 to 7 carbon atoms per molecule. They include trioses (C3H6O3), tetroses (C4H8O4), pentoses (C5H10O5), hexoses (C6H12O6) and heptoses. The most common monosaccharides are galactose, glucose and fructose. Glucose is one of the most common monosaccharides and a significant source of energy. During cellular respiration, energy is derived from glucose; this energy is utilised to make ATP (adenosine triphosphate).
These are formed by the condensation of two monosaccharide molecules with the elimination of a water molecule. They include sucrose, lactose, and maltose. The monosaccharide monomers are either the same molecule or two different molecules in them. These are called the digestible disaccharides present in food.
GIF: Formation of disaccharide
These are compounds formed by the condensation of 3 - 10 monosaccharide molecules. They are soluble in water and are commonly sweet in taste. Common examples include stachyose (Glucose + Galactose + Galactose + Fructose), and raffinose (Glucose + Galactose + Fructose).
They are complex carbohydrates formed by the polymerisation of a large number of monosaccharide monomers. They are represented as (C6H10O5)n. They are of two types as follows:
It is a polymer of one type of monosaccharide unit. Examples include glycan (made of glucose units) and fructan (composed of fructose units).
It is a polymer of more than one type of monosaccharide monomer units. Examples include agar, hemicellulose and chitin.
Lipids are fatty acid esters of alcohols and related substances. They are hydrophobic in nature and are insoluble in water. They can be dissolved in non-polar organic solvents like ether, chloroform, benzene etc. Lipids are used in the formation of cell membranes, production of hormones and can also be stored and used as fuel. The common lipids are steroids, phospholipids, carotenoids and triglycerides. Fatty acids and glycerol are the basic components of all lipids.
The chemical formula for Glycerol is C3H8O3. It contains three hydroxyl groups (-OH groups) in its chemical structure which are bound to the carbon atoms. It possesses three carbon atoms, 3 oxygen atoms, and eight hydrogen atoms.
They are organic acids with a hydrocarbon chain ending in a carboxylic group. They possess straight or ring structure and are of two types as follows:
These fatty acids contain one or more double bonds in their carbon chain. They can take up additional hydrogen and hence are called unsaturated. Examples include oleic acid, linoleic acid, linolenic acid etc.
Fig: Unsaturated fatty acids
These types of fatty acids do not have double bonds in their carbon chains and cannot take up hydrogen. They possess straight-chains and are solid at room temperature. Animal fats are usually saturated. Examples include palmitic acid, stearic acid etc.
Fig: Saturated fatty acids
These are the most abundant molecules in the cell. They are made up of carbon, hydrogen, oxygen, nitrogen and sulphur. The polymerisation of amino acids leads to the formation of proteins. In a polypeptide, the amino acids remain serially linked by peptide bonds (-CO-NH-). The various combinations of 20 amino acids results in the formation of a large number of proteins. Proteins play an important role in the production of carbohydrates and lipids as the enzymes used in the synthesis of carbohydrates and lipids are proteins. Examples include keratin proteins.
Fig: Formation of protein
These are the largest macromolecules in the living world. They are polymers of purine and pyrimidine nucleotides. The nucleotides are joined by phosphate groups. Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the two major types of nucleic acids.
Fig: Nucleic acids
These are made up of a phosphate group, a pentose sugar, and a nitrogenous base. The nitrogenous bases present in DNA include Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). But in RNA instead of Cytosine, Uracil (U) is present. All the genetic information of a cell can be found in DNA.
The following are the importance of macromolecules:
(A) Primary structure
(B) Tertiary structure
(C) Quaternary structure
(D) Secondary structure
Solution: The proteins possess 4 types of structures as follows:
The tertiary structure is formed when a long protein chain folds in on itself like a hollow woollen ball. This creates a three-dimensional image of a protein. Tertiary structure of protein is required for many of their biological functions. Hence the correct option is B.
Fig: Tertiary structure
(D) All of the above
Solution: Macromolecules or biomacromolecules are acid insoluble fractions which have molecular weight ranging from ten thousand daltons and above. The true macromolecules are formed by the acid insoluble polysaccharides, polypeptides and polynucleotides. Polysaccharides are macromolecules made up of long chains of sugars. They are made up of smaller units called monosaccharides. Polypeptides are proteins which are made up of long chains of amino acids bound together by the peptide bonds. Polynucleotides are nucleic acids which are formed by the building blocks known as nucleotides. The nucleotides are made up of nitrogenous base, sugar molecule and phosphate group. Hence the correct option is D.
(A) Carbon and oxygen atoms of two adjacent monosaccharides
(B) Carbon and hydrogen atoms of two adjacent monosaccharides
(C) Hydrogen and oxygen atoms of two adjacent monosaccharides
(D) Two carbon atoms of two adjacent monosaccharides
Solution: A glycosidic bond is formed between two carbon atoms of two monosaccharides lying adjacent to each other. This results in the formation of polysaccharides by giving out a water molecule. Hence, it is a dehydration reaction. So the correct option is D.
GIF: Formation of disaccharide
Answer: The following are the major roles of macromolecules:
Answer: DNA or deoxy ribonucleic acid is considered as the largest macromolecule in the living world.
Answer: Polyethylene (PE) with the simplest basic structure, a repetition of CH2 units, is the largest polymer.
Answer: Cotton fibres are the purest form of cellulose. It is the most abundant polymer in nature. Nearly 90% of the cotton fibres are cellulose.
Answer: HDL (high-density lipoprotein) is considered as the good cholesterol. It absorbs cholesterol and carries it back to the liver from there it is flushed out. High levels of HDL cholesterol can reduce the risk for heart diseases.