Chemistry In Everyday life - Chapter 16 - Class 12

Chemistry plays a very important role in our daily life. Chemistry Compounds are used in every aspect of our life, they are used for cleansing purposes in food for flavouring and prevention in medicins, etc.

1.1 Drugs 

Drugs are the chemicals of low molecular masses (~100-500 u). These interact with macromolecular targets and produce a biological response. If taken in a higher dose than recommended, they may act as a potential poison and hence, may cause a poisonous effect.

Drug which produces a therapeutic effect and useful biological response are called medicines. Medicines are used in diagnosis, prevention and treatment of diseases.

The treatment of a disease can be done with help of chemicals. Hence, the use of chemicals for therapeutic effect is called chemotherapy.

Classification of Drugs

Drugs can be classified on the basis of

1. Drug action Based on the action of a drug on particular biochemical process. e.g., antihistamines.
2. Pharmacological effect It provides whole range of drugs available for the treatment of a particular type of problem. e.g., analgesics. 
3. Chemical Structure Drugs classified in this way share common structural features and sometimes have similar pharmacological activity. e.g., sulphonamides.
4. Molecular targets Based on interaction with biomolecules or target molecules like carbohydrates, lipids, proteins and nucleic acids.

Drug-Target Interaction

1. Catalytic action of enzymes: The first function of an enzyme is to hold the substrate for a chemical reaction. The second function of an enzyme is to provide functional groups that will attack the substrate and carry out a chemical reaction. 
2. Drug enzyme interaction: Drug can inhibit the attachment of substrate on active site of the enzyme in two ways. 
   • By competing with natural substrate for their attachment on active sites of enzymes, called as competitive inhibitors.
   • By binding with allosteric site which changes the shape of active site in such a way that substrate cannot recognise it. 

Therapeutic Action of Different Classes of Drugs

On the basis of therapeutic action, drugs are classified as follows

1. Antacids: Substances which neutralise the excess of hydrochloric acid and raise the pH to an appropriate level in stomach are called antacids, e.g., ranitidine (Zantac), cimetidine (tegument).
2. Antihistamines: Drugs which interfere with the natural action of histamine by competing with it for binding sites of receptor where histamine exerts its effect are called antihistamines. e.g., brompheniramine.
3. Tranquillize: Drugs which are used to reduce tension and provide relief from mental diseases are called tranquilizers. e.g., chlordiazepoxide.
4. Analgesics: Neurologically, active drugs which reduce or abolish pain without causing impairment of consciousness mental confusion, incoordination or paralysis or without causing any other disturbance of the nervous system are called analgesics. e.g., aspirin.
   Analgesics are classified as follows 
   • Non-narcotic analgesics,e.g., aspirin is also used as antipyretics (to reduce body temperature).
   • Narcotic analgesics (e.g., morphine)
   NOTE Tranquilizers and analgesics are neurologically active drugs.
5. Antimicrobials: Drugs used to cure diseases caused by bacteria, fungi and viruses are called antimicrobials.
   These are the following types
   • Antibiotics The Chemical substances produced wholly or partially by chemical synthesis, which in low concentration either kill or inhibit the growth of microorganisms by intervening in their metabolic processes are called antibiotics. e.g., penicillin.
     
     • bactericidal (that kills the microorganisms, e.g., penicillin)
     • bacteriostatic (either inhabit or arrest the growth of microorganisms, e.g., chloramphenicol)
     Board Spectrum antibiotics
     (e.g., chloramphenicol) kill or inhabit a wide range of gram-positive and gram-negative bacteria while narrow-spectrum antibiotics (e.g., penicillin G) are effective against a short range of gram-positive or gram-negative bacteria. If an antibiotic is effective against a single microorganism, it is referred to as limited spectrum antibiotics.
   • Antiseptics (that kill microorganisms and are harmful to living tissues, e.g., Dettol tincture of iodine, 0.2% solution of phenol, bithionol etc.).
   • Disinfectants (that kill microorganisms and are harmful to living tissues, e.g., 1% solution of phenol).
6. Antifertility drugs are used to control the population. These contain a mixture of synthetic estrogen and progesterone derivatives.

1.2 Other Useful Chemicals of Daily Life

Preservatives

Preservatives are the chemical which is added to food to prevent their spoilage due to microbial growth, e.g., sodium benzoate, table salt.

Artificial Sweeteners

Artificial Sweeteners are the chemical that gives sweetening effect to the food without producing any calories, so useful for diabetic person. Saccharin, aspartame, alitame, sucralose, etc. are examples of artificial sweeteners. Aspartame is unstable at cooking temperature so, its use is limited to cold foods and soft drinks.

Cleansing agents

Soaps and detergents are cleansing agents, also called surfactants. These days, synthetic detergents get preference over soaps because they work even in hard water.

Soaps

Soaps are sodium or potassium salts of long-chain fatty acids and are prepared by a process called saponification, in which fat reacts with alkalis.

Detergents

Synthetic detergents are called soapless soap (as they have all the properties of soaps but actually do not contain any soap) and are of three types:

1. Anionic detergents: These are sodium salts of sulphonated long chain alcohols or hydrocarbons, e.g., sodium dodecylbenzene sulphonate. these are used in toothpaste and household works.
2. Cationic detergents These are quaternary ammonium salts of amines with acetates, chlorides or bromides as anions, e.g., cetyltrimethylammonium bromide. These have germicidal properties. 
3. Non-Ionic detergents They do not contain any ion in their constitution, e.g., liquid dish-washing detergents.

NOTE:

Straight chain detergents are biodegradable, i.e. degraded by microorganisms, while branched-chain detergents are non-biodegradable and cause environmental pollution.

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