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CBSE Class 12 Chemistry Notes

Chemistry in Everyday Life

Chemistry in Everyday Life

  1. Drugs are low molecular mass ( 100-500 u) substances which interact with targets in the body and produce a biological response.
  2. Medicines are chemicals that are useful in diagnosis, prevention and treatment of diseases.
  3. Desirable or beneficial effect of a drug like treatment of symptoms and cure of a disease on a living body is known as therapeutic effect.
  4. Proteins which perform the role of biological catalysts in the body are called enzymes.
  5. Functions of enzymes :
    Enzymes
    1. The first function of an enzyme is to hold the substrate for a chemical reaction. Active sites of enzymes hold the substrate molecule in a suitable position, so that it can be attacked by the reagent effectively.
    2. The second function of an enzyme is to provide functional groups that will attack the substrate and carry out chemical reaction.
  6. Main role of drugs is to either increase or decrease role of enzyme catalysed reactions. Inhibition of enzymes is a common role of drug action. Enzyme inhibitor is drug which inhibits catalytic activity of enzymes or blocks the binding site of the enzyme and eventually prevents the binding of substrate with enzyme. Drug can inhibit attachment of substrate on active site of enzymes in following ways.
    1. Competitive Inhibition : Competitive Inhibitors are the drugs that compete with the natural substrate for their attachment on the active sites of enzymes.
      Competitive Inhibition
    2. Non-Competitive Inhibition : Some drugs do not bind to the enzyme’s active site, instead bind to a different site of enzyme called allosteric site. This binding of inhibitor at allosteric site changes the shape of the active site in such a way that substrate cannot recognise it. If the bond formed between an enzyme and an inhibitor is a strong covalent bond and cannot be broken easily, then the enzyme is blocked permanently. The body then degrades the enzyme-inhibitor complex and synthesizes the new enzyme
      Non-Competitive Inhibition
  7. Receptors as Drug Targets : Competitive Inhibitors are the drugs that compete with the natural substrate for their attachment on the active sites of enzymes.

    Proteins which are vital for communication system in the body are called receptors. In the body, message between two neurons and that between neurons to muscles is communicated through chemical messengers. They are received at the binding sites of receptor proteins. To accommodate a messenger, shape of the receptor site changes which brings about the transfer of message into the cell. Chemical messenger gives message to the cell without entering the cell.
    Receptors as Drug Targets

    Receptors show selectivity for one chemical messenger over the other because their binding sites have different shape, structure and amino acid composition.

    Drugs that bind to the receptor site and inhibit its natural function are called antagonists. These are useful when blocking of message is required. Drugs that mimic the natural messenger by switching on the receptor are called agonists. These are useful when there is lack of natural chemical messenger.

  8. Therapeutic action of different classes of drugs
    1. Antacid : Chemical substances which neutralize excess acid in the gastric juices and give relief from acid indigestion, acidity, heart burns and gastric ulcers.

      Examples: Eno, gelusil, digene etc

    2. Antihistamines : Chemical substances which diminish or abolish the effects of histamine released in body and hence prevent allergic reactions.

      Examples: Brompheniramine (Dimetapp) and terfenadine (Seldane)

    3. Neurologically Active Drugs : Drugs which have a neurological effect i.e. affects the message transfer mechanism from nerve to receptor
      1. Tranquilizers : Chemical substances used for the treatment of stress and mild or severe mental diseases.

        Examples: Derivatives of barbituric acids like veronal, amytal, nembutal, luminal, seconal

      2. Analgesics : Chemical substances used to relieve pain without causing any disturbances in the nervous system like impairment of consciousness, mental confusion, incoordination or paralysis etc.

        Classification of Analgesics :

        Non-narcotic analgesics Narcotic analgesics
        They are non-addictive drugs When administered in medicinal doses, these drugs relieve pain and produce sleep
        Examples: Aspirin, Ibuprofen, Naproxen, Dichlofenac Sodium Examples: Morphine and its derivatives
    4. Antimicrobials : Drugs that tends to destroy/prevent development or inhibit the pathogenic action of microbes such as bacteria (antibacterial drugs), fungi (antifungal agents), virus (antiviral agents), or other parasites (antiparasitic drugs) selectively

      Types of antimicrobial drugs

      1. Antibiotics : Chemical substances produced by microorganisms that kill or prevent the growth of other microbes.

        Classification of antibiotics on basis of mode of control of microbial diseases

        Bactericidal Bacteriostatic
        Drugs that kills organisms in body Drugs that inhibits growth of organisms
        Examples : Penicillin, Aminoglycosides, Ofloxacin Examples : Erythromycin, Tetracycline, Chloramphenicol

        Classification of antibiotics on basis of its spectrum of action

        Broad spectrum antibiotics Narrow spectrum antibiotics Limited spectrum antibiotics
        Antibiotics which kill or inhibit a wide range of Gram-positive and Gram-negative bacteria Antibiotics which are effective mainly against Gram-positive or Gram-negative bacteria Antibiotics effective against a single organism or disease
        Examples: Ampicillin and Amoxycillin Examples: Penicillin G  
      2. Antiseptics : Chemical substances that kill or prevent growth of microorganisms and can be applied on living tissues such as cuts, wounds etc.

        Examples: Soframicine, dettol

      3. Disinfectants: Chemical substances that kill microorganisms but cannot be applied on living tissues such as cuts, wounds etc.

        Examples: Chlorine (Cl2), bithional, iodoform etc.

    5. Antifertility Drugs : Chemical substances used to prevent conception or fertilization.

      Examples: Norethindrone, ethynylestradiol (novestrol)

  9. Food additives are the substances added to food to preserve its flavour or improve its taste and appearance

    Different types of food additives :

    No. Name of food additive Examples
    1 Artificial Sweetening Agents : Chemical compounds which gives sweetening effect to the food and enhance its flavour Aspartame, Sucrolose and Alitame
    2 Food preservatives : Chemical substances which are added to food material to prevent their spoilage due to microbial growth Sugar, Salts, Sodium benzoate
    3 Food colours : Substances added to food to increase the acceptability and attractiveness of the food product Allura Red AC, Tartrazine
    4 Nutritional supplements : Substances added to food to improve the nutritional value Vitamins, minerals etc.
    5 Fat emulsifiers and stabilizing agents : Substances added to food products to give texture and desired consistency Egg yolk (where the main emulsifying chemical is Lecithin)
    6 Antioxidants :Substances added to food to prevent oxidation of food materials Butylated Hydroxy Toluene (BHT),
    Butylated Hydroxy Anisole (BHA)
  10. Soaps :
    1. Soap : It is a sodium or potassium salts of long chain fatty acids like stearic, oleic and palmitic acid.
      Soap
    2. Types of soaps :
      No. Descriptions
      1 Medicated soaps : These soaps are the soft soaps containing substances with medicinal properties. Neem soap, carbolic soaps are some common examples of medicated soaps.
      2 Shaving soaps : These soaps are potassium sodium stearates and produce lasting lather. These contain glycerol to prevent rapid drying. A gum called rosin is added in these soaps which forms sodium rosinate which lathers well.
      3 Transparent soaps : These soaps are prepared by dissolving the soap in ethanol and then evaporating the excess solvent
      4 Floating soaps : These soaps float in water and are prepared by beating tiny air bubbles into the product before it hardens
      5 Soap chips : These are prepared by running a thin sheet of melted soap onto a cool cylinder and scrapping off the soaps in small broken pieces.
      6 Soap granules : These are dried miniature soap bubbles.
      7 Soap powder and scouring soaps : These substances contain some soap, a scouring agent (abrasive) such as powdered pumice or finely divided sand and builders like sodium carbonate and trisodium phosphate. Builders help the soaps in its cleaning action
    3. Advantages of using soaps : Soap is a good cleansing agent and is 100% biodegradable i.e., micro- organisms present in sewage water can completely oxidize soap. Therefore, soaps do not cause any pollution problems.
    4. Disadvantages of using soaps :
      1. Soaps cannot be used in hard water because hard water contains metal ions like Ca2+ and Mg2+ which react with soap to form white precipitate of calcium and magnesium salts. These precipitates stick to the fibres of the cloth as gummy mass and block the ability of soaps to remove oil and grease from fabrics. Therefore, it interferes with the cleansing ability of the soap and makes the cleansing process difficult.
        Disadvantages Soap
      2. In acidic medium, the acid present in solution precipitate the insoluble free fatty acids which adhere to the fabrics and hence block the ability of soaps to remove oil and grease from the fabrics. Hence soaps cannot be used in acidic medium.
  11. Detergents :
    1. Detergents are sodium salts of long chain of alkyl benzene sulphonic acids or sodium salts of long chain of alkyl hydrogen sulphates
      Detergents
    2. Classification of detergents :
      1. Anionic detergents :

        Anionic detergents are sodium salts of sulphonated long chain alcohols or hydrocarbons. Alkyl hydrogensulphates formed by treating long chain alcohols with concentrated sulphuric acid are neutralised with alkali to form anionic detergents. Similarly alkyl benzene sulphonates are obtained by neutralising alkyl benzene sulphonic acids with alkali.

        Example:
        Detergents

        Anionic detergents are termed so because a large part of molecule is an anion.

        Uses : They are used in household cleaning like dishwasher liquids, laundry liquid detergents, laundry powdered detergents etc.

        Advantage : They are effective in slightly acidic solutions where soaps do not work efficiently

      2. Cationic detergents :

        Cationic detergents are quarternary ammonium salts of amines with acetates, chlorides or bromides as anions. Cationic parts possess a long hydrocarbon chain and a positive charge on nitrogen atom.

        Example:
        Detergents

        Cationic detergents are termed so because a large part of molecule is a cation.

        Use : Since they possess germicidal properties, they are used as germicides

        Advantage : They has strong germicidal action

        Disadvantage : These detergents are expensive

      3. Non- ionic detergents :

        They do not contain any ion in their constitution. They are like esters of high molecular mass.

        Example : Detergent formed by condensation reaction between stearic acid reacts and polyethyleneglycol
        Detergents

        Use : Making liquid washing detergents

        Advantage : They have effective H- bonding groups at one end of the alkyl chain which make them freely water soluble.

  12. Biodegradable detergents : Detergents having straight hydrocarbon chains that are easily decomposed by microorganisms.

    Example: Sodium lauryl sulphate

  13. Non-Biodegradable detergents : Detergents having branched hydrocarbon chains that are not easily decomposed by microorganisms
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