By now, you have learnt the basic principles of chemistry and also realised that it influences every sphere of human life. The principles of chemistry have been used for the benefit of mankind. Think of cleanliness — the materials like soaps, detergents, household bleaches, tooth pastes, etc. will come to your mind. Look towards the beautiful clothes — immediately chemicals of the synthetic fibres used for making clothes and chemicals giving colours to them will come to your mind. Food materials — again a number of chemicals about which you have learnt in the previous Unit will appear in your mind. Of course, sickness and diseases remind us of medicines — again chemicals. Explosives, fuels, rocket propellents, building and electronic materials, etc., are all chemicals. Chemistry has influenced our life so much that we do not even realise that we come across chemicals at every moment; that we ourselves are beautiful chemical creations and all our activities are controlled by chemicals. In this Unit, we shall learn the application of Chemistry in three important and interesting areas, namely – medicines, food materials and cleansing agents.
Drugs and their Classification
Drugs are chemicals of low molecular masses (~100 – 500u). These interact with macromolecular targets and produce a biological response. When the biological response is therapeutic and useful, these chemicals
are called medicines and are used in diagnosis, prevention and treatment of diseases. If taken in doses higher than those recommended, most of the drugs used as medicines are potential poisons. Use of chemicals for therapeutic effect is called chemotherapy,
Classification of Drugs
Drugs can be classified mainly on criteria outlined as follows:
(a) On the basis of pharmacological effect
This classification is based on pharmacological effect of the drugs. It is useful for doctors because it provides them the whole range of drugs available for the treatment of a particular type of problem. For example, analgesics have pain killing effect, antiseptics kill or arrest the growth of microorganisms. (b) On the basis of drug action It is based on the action of a drug on a particular biochemical process. For example, all antihistamines inhibit the action of the compound, histamine which causes inflammation in the body. There are various ways in which action of histamines can be blocked. You will learn about this in Section 16.3.2.
(c) On the basis of chemical structure
It is based on the chemical structure of the drug. Drugs classified in this way share common structural features and often have similar pharmacological activity. For example, sulphonamides have common structural feature, given below.
(d) On the basis of molecular targets
Drugs usually interact with biomolecules such as carbohydrates, lipids, proteins and nucleic acids. These are called target molecules or drug targets. Drugs possessing some common structural features may have the same mechanism of action on targets. The classification based on molecular targets is the most useful classification for medicinal chemists.
Exercises
16.1 Why do we need to classify drugs in different ways ?
16.2 Explain the term, target molecules or drug targets as used in medicinal chemistry.
16.3 Name the macromolecules that are chosen as drug targets.
16.4 Why should not medicines be taken without consulting doctors ?
16.5 Define the term chemotherapy.
16.6 Which forces are involved in holding the drugs to the active site of enzymes ?
16.7 While antacids and antiallergic drugs interfere with the function of histamines, why do these not interfere with the function of each other ?
16.8 Low level of noradrenaline is the cause of depression. What type of drugs are needed to cure this problem ? Name two drugs.
16.9 What is meant by the term ‘broad spectrum antibiotics’ ? Explain.
16.10 How do antiseptics differ from disinfectants ? Give one example of each.
16.11 Why are cimetidine and ranitidine better antacids than sodium hydrogencarbonate or magnesium or aluminium hydroxide ?
16.12 Name a substance which can be used as an antiseptic as well as disinfectant.
16.13 What are the main constituents of dettol ?
16.14 What is tincture of iodine ? What is its use ?
16.15 What are food preservatives ?
Please refer to attached file for NCERT Class 12 Chemistry Chemistry in Everyday Life
