Chemistry NCERT Exemplar Solutions Class 12th Chapter Sixteen: Overview, Questions, Preparation

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(d) Antiseptics are applied to the living tissues such as wounds, cuts and diseased skin surfaces. Antiseptic medicines such as antibiotics cannot be ingested.

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(c) Birth control pills contain a mixture of estrogen and progesterone derivatives. Both of these are sex hormones. Progesterone suppresses ovulation and estrogen control the menstrual cycle.

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(a) Aspirin inhibits the synthesis of compounds known as prostaglandins which stimulate inflammation in the tissues and cause pain. So, it is effective in relieving pain.

Aspirin has many other effects such as reducing fever (antipyretic) and preventing blood platelet coagulation. Because of this anti-blood clotting action, it is widely used to prevent heart.attacks. It does not make a person addictive as it is non-narcotic drug.

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(c) The most useful classification of drugs for medicinal chemists. It is on the basis of molecular targets. Target molecules are usually biomolecules like carbohydrates, lipids, proteins and nucleic acids. These drugs possess some common structural features, may have the same mechanism of action on a specific drug target.

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(a) Tranquilizers are neurologically active drugs. Some tranquilizers are antidepressants and the functions by inhibiting the enzymes which catalyse the degradation of noradrenaline.

If the enzyme is inhibited, the neurotransmitter noradrenaline is slowly metabolized and can thus activate the receptor for longer periods there by counteracting the effect of depression. Tranquilizers form an essential component of sleeping pills.

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(a) Salvarsan is arsenic containing drug which was first used for treatment of syphilis. Syphilis is an acute and chronic infections disease caused by the bacterium Treponema pallidum. It is a sexually transmitted infection. The primary route of transmission is through sexual contact but it may also be transmitted from mother to foetus during pregnancy or at birth.

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(a) A narrow spectrum antibiotic is active against gram positive or gram negative bacteria.

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(b) The compound that causes general antidepressant action on the central nervous system belongs to the class of tranquilizers.

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(d) All soaps are made by boiling fats or oils with suitable hydroxide. Variations are made by adding different raw materials. Sodium laurylsulphate and sodium dodecylbenzenesulphonate are anionic detergents.

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(b) Equanil is a tranquilizer used in controlling depression and hypertension.

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(b) Shaving soaps contain glycerol to prevent rapid drying. A gum called rosin is added in these soaps which forms sodium rosinate which enhances lathering property of soap.

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(c) Glycerol is added to shaving soap to prevent rapid drying while to enhance the leathering property of soap, a gum called rosin is added to them. It forms sodium rosinate which lathers well.

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(b) Liquid dishwashing detergents are non-ionic detergents.

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(c) Polyethyleneglycols are used in the preparation of non-ionic detergents.

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(c) Drugs usually interact with biomolecules such as carbohydrates, lipids, proteins and nucleic acids. These are called drug targets. Vitamins are not a target molecule for drug function in body.

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(c) Inhibitors are chemical substances which tend to reduce the activity of a particular enzyme. Generally, a weak bond such as H-bonding, van there Waals interaction, etc. is formed between the enzyme and the inhibitor.

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(d) Sucralose is an artificial sweetening agent which is 600 times sweeter than sucrose and does not provide calories.

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(b) Artificial sweeteners are non-caloric substitutes for sugar. They are often intensely more sweet than sugar but do not enhance nutritional value of food. Vitamins and minerals are essential nutrients because they perform hundreds of roles in the body.

Amino acids will also enhance the nutritional value of food.

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(b, d) Receptor proteins are embedded in the cell membrane and their active sites project outside region of the cell membrane. Shape of the receptor changes during the attachment of messenger.

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(b, d) Table salt and cane sugar are used, as food preservatives while sodium hydrogen carbonate and benzoic acid are not used as food preservatives.

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(b, c)

(a) CHCl₃  (chloroform) was used as an anaesthesia in surgery but now it is used in the production of the Freon refrigerant R-22.

(b) Iodoform (CFH₃) produces iodine on coming in contact with skin, so it is used as an antiseptic for wounds.

(c) Boric acid (IT₃BO₃) in dilute aqueous solution is a weak antiseptic for eyes. Thus, chemical messenger gives message to the all without entering the cell.

(d) Chlorine in the concentration of 0.2 of 0.4 ppm in aqueous solution and sulphur dioxide in very low concentrations, are disinfectants.

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(a, b) Barbiturates are tranquilizers which are used as hypnotics or sleep inducing agents.

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(a, b)

(a) Sulphapyridine is a sulphonamide antibacterial drug.

(b) Prontosil is also called sulphamidochrysoidine.

(c) Salvarsan is arsenic based antibacterial drug.

(d) Nardil is an antidepressant drug.

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(a, b, c)

(a) Iproniazid is a hydrazine drug used as an antidepressant.

(b) Phenelzine is also known as Nardil. It is used in the treatment of major depressive disorder.

(c) Equanil is used in controlling depression and hypertension.

(d) Salvarsan is an antibacterial drug. It is used in the treatment of Syphilis.

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(c, d) Penicillin destroys bacteria by destroying the cell wall of the microorganism or kill the bacteria so, it has bacteriocidal effect. Penicillin has a narrow or limited spectrum.

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(b, d) Sodium Hydrogen carbonate and Magnism Hydroxide, both are mild alkalies, are used as ant-acids.

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(a, d) Ranitidine and cimetidine are antihistamines which are used as ant-acids. These drug result in release of lesser amount of acid. Brompheniramine and terfenadine are antihistamines which act as antiallergic in drugs.

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(a, d) Tranquilizers are neurologically active drugs. Veronal and luminal are derivatives of barbituric acid used as tranquilizers.

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(a, d) Sodium salts of sulphonated long chain alcohol and sodium salts of sulphonated long chain hydrocarbons are anionic detergents e.g., Sodium laurylsulphate CH₃ (CH₂)₁₀CH₂OSO₃^– Na⁺ and sodium dodecylbenzene sulphonate.

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(a, c, d)

(a) Cationic detergents are quaternary ammonium salts of amines with acetates, chlorides or bromides as anions. These detergents have germicidal properties.

(b) Bacteria cannot degrade the detergents containing highly branched chains, therefore, in most of the detergents used these days, the branching is kept to a minimum so that the detergents become easily biodegradable.

(c) Some synthetic detergents can give foam even in ice cold water.

(d) Synthetic detergents are cleansing agents which have all the properties of soaps, but which actually do not contain any soap.

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The average molecular mass of drugs is of the order of 100-500 u.

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Medicines are used in diagnosis, prevention and treatment of diseases.

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Antiseptics are chemicals which either kill or prevent the growth of micro-organisms and are applied to the living human tissues.

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Antiseptics, antibiotics, disinfectants and sulpha drugs come under antimicrobial drugs.

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Receptors are embedded on the outer surface of the cell membrane.

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Hyperacidity in the intestine creates ulcer, gastric reflux and oesophagitis.

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Sites different from active site of enzyme where a molecule can bind and affect the active site is called allosteric site. Some drugs may also bind at this site.

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Ionic bonding, hydrogen bonding, van there Waals interaction, dipole-dipole interaction, etc., are involved in binding.

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Antibiotic, arsphenamine possesses -As = As – linkage that resembles -N =N – linkages in azo dyes.

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Tranquilizers are used in sleeping pills.

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Aspirin prevents platelet coagulation and thus has antiblood clothing action, therefore, can prevent blood clotting in heart.

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Antihistamines are the drugs which control the allergy effects produced by histamines. Antacids are the substances which neutralise gastric acidity. Antihistamine do not affect the secretion of acid in stomach and the reason is that both antiallergic and antacid drugs work on different receptors.

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Soft soaps are potassium salts of fatty acids (such as palmitic acid, stearic acid and oleic acid).

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Acid-base titration can be used to determine the excess amount of alkali in soap. The excess alkali left after hydrolysis of oils or fats can be the source of alkalinity in soap.

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Detergents (which are not biodegradable) persist in water even after sewage treatment and that causes foaming in river water.

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Anionic detergents such as cetyltrimethyl ammonium bromide are used in hair shampoos and hair conditioners.

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Cationic detergents such as cetyltrimethyl ammonium bromide are used in hair shampoos and hair conditioners.

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Non-ionic detergents such as polyethylene glycol stearate are used as dishwashing soaps.

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Micelle formation of the detergent can be shown as:

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Straight chain hydrocarbons in synthetic detergent leads to easy biodegrad-ability because the branched chain hydrocarbon tail is a source of pollution. Therefore, lesser the branching more is the biodegradability.

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Soaps are biodegradable. The detergents are quite stable and are non- biodegradable because of branching in hydrocarbon chain hence cause water pollution. Therefore, it is safer to use soap from the environmental point of view.

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Analgesics are neurologically active pain killing drugs that reduce pain without causing impairment of consciousness, mental confusion, co¬ordination or paralysis or some other disturbances of nervous system. For example, aspirin, ibuprofen, paracetamol, diclofenac sodium, etc.

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A person suffers from depression when he has low levels of noradrenaline. Noradrenaline is a neurotransmitter which plays a role in mood changes. Low level of noradrenaline lowers the signal-sending activity and make the person suffer from depression.

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Antiseptics are applied to living tissues whereas disinfectants are applied to non-living objects such as drains, toilets, floors and utensils.

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Magnesium hydroxide is a better antacid because being insoluble, it does not allow the pH to increase above neutral. However, sodium hydrogen carbonate (NaHCO₃) being soluble, its excess can make the stomach alkaline and trigger the production of even more acid.

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Narcotic analgesics which are obtained from opium poppy are called opiates. Examples are morphine and its derivatives like codeine and heroin (morphine diacetate).

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The narcotic drugs relieve pain and produce sleep. Therefore, these are commonly used for the relief of postoperative pain, cardiac pain and pain of terminal cancer and in child birth.

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Drugs that bind to the receptor site and inhibit its natural function are called antagonistic drugs. For example, cimetidine antacid drug.

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Antimicrobial drugs can kill the microorganism such as bacteria, fungi, viruses or other parasites. They can, alternatively inhibit the pathogenic action of microbes.

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Glycerol is obtained as a side product during the formation of soaps.

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Bathing soaps are potassium salts of long chain fatty acids. They are usually soft and also free from unused alkali. While washing soaps are sodium salts of long chain fatty acids. They are usually hard and also contain some residual alkali.

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Transparent soaps are prepared by dissolving the soap in ethanol and then evaporating the excess solvent.

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Antacids neutralise the acid produced in the stomach. They do not control the cause of production of excess acid. Therefore, antacids control only the symptoms but not the cause. On the other hand, antihistamines are the drugs which suppress the action of histamine which is the chemical responsible for stimulation of secretion of pepsin and HCl in the stomach. These influence and prevent the binding of histamine with the receptors present in the stomach wall resulting in lower acid production and therefore, better treatment. This is the advantage of antihistamines over antacids.

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Histamine is a potent vasodilator. It contracts muscles in the gut and bronchi. It relaxes some other muscles e.g., in the'walls of fine blood vessels. Histamine is also responsible for congestion in the nose associated with common cold and allergies. Histamine stimulates the release of pepsin and hydrochloric acid in the stomach.

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Noradrenaline plays an important role in mood change. If the level of noradrenaline is low, the person suffers from depression.

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Enzymes have active sites that bind the substrate for effective and quick chemical reaction. The functional groups present at the active site of enzyme react with functional groups of substrate via .ionic bonding, van there Waals' interaction, etc. Some drugs interfere with this interaction by blocking the binding site of enzyme and also prevent the binding of actual substrate with enzyme. This inhibits the catalytic activity of the enzyme. Therefore, these are called inhibitors.

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Some substances are added to soap to affect the properties in order to make it useful for a particular application, are called fillers. For example, glycerol is added in shaving soaps, to prevent it from rapid drying. Laundry soaps contain fillers like sodium rosinate, sodium silicate, borax and sodium carbonate to increase their leather forming ability. In medicated soaps, substances of medicinal value are added. In some soaps deodorants are also added.

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In low calorie drinks, some artificial sweetening agents (like aspartame, alitame, sucralose, saccharin etc.) are present which are often many hundred times sweeter than sugar but do not metabolise and hence, do not produce any energy.

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Table salt, sugar vegetable oils and sodium benzoate, etc. are used as preservatives. These do not allow moisture and air to enter the material and hence, bacteria cannot thrive on them. Therefore, pickles do not get spoiled for months.

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Saccharin (o-sulpho benzoicimide) is an artificial sweetener, whereas saccharic acid (dicarboxylic acid) is obtained by the oxidation of glucose with cone. HNO₃ or by bacterial oxidation.

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Sucralose is trichloro derivative of sucrose. It is about 600 times sweeter than sucrose. However, it neither provides calories nor causes tooth decay.

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Aspartic acid and phenylalanine are two a-amino acids which form the methyl ester of dipeptide and named as aspartame (an artificial sweetener) which is 100 times more sweet than cane sugar.

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Since aspartame is unstable and decomposes at cooking temperature, therefore, it is used as a sweetening agent in cold foods and soft drinks.

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Sodium salts of benzoic acid, sorbic acid and propanoic acid, etc., are used as food preservatives.

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Some drugs do not bind to the enzyme's active site. These bind to a different site of enzyme which is called allosteric site. This bonding of inhibitor at allosteric site changes the shape of the active site in such a way that substrate cannot recognise it. As a result, the affinity of the substrate for the active site is reduced.

It may be noted that if the bond formed between enzyme and inhibitor is strong covalent bond and therefore cannot be broken easily, then the enzyme gets blocked permanently. The body then degrades the enzyme inhibitor complex and synthesizes new enzyme.

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Receptor proteins are embedded in cell membranes in such a way that their small part possessing active sites projects out of the surface of the membrane and opens on the outside region of the cell membrane.

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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 synthesises the new enzyme.

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(i) → (c) (ii) → (d) (iii) → (a) (iv) → (b)

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(i) → (b) (ii) → (a) (iii) → (d) (iv) → (c)

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(i) → (c) (ii) → (d) (iii) → (b) (iv) → (a)

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(i) → (c) (ii) → (d) (iii) → (b) (iv) → (a)

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(i) → (b) (ii) → (d) (iii) → (a) (iv) → (e) (v) → (c)

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(i) → (e) (ii) → (f) (iii) → (d) (iv) → (g) (v) → (b) (vi) → (a) (vii) → (c)

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(c) Penicillin (G) is not a broad spectrum antibiotic so it is not effective against some gram positive and gram negative bacteria.

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(d) Salvarsan is an antibacterial drug containing arsenic and it does not contain sulphonamide group.

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  (a) Neurotransmitters are small molecular which bind to the receptor for a very short time to transfer message to it and depart quickly unchanged after transferring the message, the receptor then forwards the message inside the cell. Receptors are proteins and they participate in the communication system of our body.

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(d) Drugs compete with natural substrate by attaching by weak bonds such as ionic bonding. H-bonding, van there Waals interaction, etc., to the active site of the enzyme.

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  (d) Chemicals bind to the receptors sites present on the surface of the membrane on the cell, but never enter the cell through receptor.

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  (d) Ethanol removes air and moisture which scatter light.

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  (a) Hydrolysis of esters of long chain fatty acids by alkali gives soap a colloid. The process is called saponification.
Sodium chloride is added to precipitate soap which is in colloidal form.

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(d) In competitive inhibition, inhibitor binds to the active site of the enzyme.

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  (e) Non-competitive inhibitors inhibit the catalytic activity of enzyme by binding with its allosteric site.

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(b) Chemical messenger gives message to the cell without entering the cell because it is received at the binding site of the receptor.

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  (d) Chemical messenger binds the receptor site and gives the message to the cell without entering the cell.

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(c) Chemicals which are added to food items to prevent them from spoiling against bacteria yeast and moulds are called food preservatives. They do not increase nutritive value of food.

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(b) Preservatives are added to the food items because they inhibit the growth of microorganisms.

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(b) Artificial sweeteners do not provide any calories because they are inert and do not metabolise in the body.

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Both prontosil and Salvarsan and antibacterial drugs (antimicrobials) discovered by Paul Ehrlich. Salvarsan is also known as arsphenamine. It is an organoarsenic molecule and has -As = As- double bond.

Salvarsan and prontosil show similarity in their structure. Both of these drugs are antimicrobials. Salvarsan contains -As = As- linkage whereas prontosil has -N = N- linkage.

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Enzymes catalyse many reactions by

(i) Holding the substrate for a chemical reaction. Active sites hold the substrate molecule in a suitable positions So that it can be attacked by the reagent effectively. Substrates bind to the active site of enzyme through ionic or hydrogen bonding or van there Waals or dipole-dipole, interactions.

(ii) Enzyme provides functional groups that will attack the substrate to carry out the chemical reaction. This function is carried out chemical reaction: This function iscarried out by some other amino acid residues of protein present on the active site of the enzyme. These free amino group to attack the substrate and bring about chemical reaction. Drugs can inhibit these activities by blocking site of enzyme and prevent the binding of substrate. Such drugs are called enzyme inhibitors.

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Synthetic detergents are cleansing agents which have all the properties of soaps, but which actually do not contain any soap. These can be used both in soft and hard water as they given foam even in hard water. Detergents can be classified into three groups according their chemical nature.

(i) Anionic detergents – These are sodium salts of sulphonated long chain alcohols or hydrocarbons and sodium alkyl benzene sulphonates. e.g., CH₃ (CH₂)₁₀CH₂OSO₃^– Na⁺
Anionic part of these detergents is involved in cleansing action.

(ii) Cationic detergents – These are quaternary ammonium salts of amines with acetates, chlorides or bromides as anions.

(iii) Non-ionic detergents – These do not contain any ion in their constitution, e.g., detergent formed by steric acid and polyethylene glycol. CH₃ (CH₂)₁₆C00 (CH₂CH₂0)_nCH₂CH₂OH.

 

Pollution by synthetic detergents can be minimized by reducing the branching of hydrocarbon chain or using unbranched hydrocarbons.

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Enzyme inhibitors block the binding site of enzyme and prevent the binding of substrate and then inhibit the catalytic activity of enzyme. They act in two different ways.

(i) Drugs which compete with substrate for their attachment on the active sites of enzymes are called competitive inhibitor.

(ii) Some drugs bind to a different site of enzyme called allosteric site. It changes the shape of the active site and substrate cannot recognize it. Such enzymes are called non-competitive inhibitor the bond formed between enzyme and an inhibitor is strong covalent bond then enzyme is blocked permanently.