Chemistry Important Questions: Chemistry in Everyday Life (3 Marks)

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Section C – Questions of 3 Marks (SA II)

Q1. Define the term Drug. State the ways of classification of drugs.

  • The word dug is derived from a French word drogue which means a dry herb. Drugs are chemicals of low molecular mass which interact with macromolecular targets and produce a biological response.
  • Example: Aspirin, Naproxen

Classification  Based on Pharmacological Effects:

  • This classification of drugs is based on the choice of drug and its pharmacological effect. This classification gives a whole range of drugs available for the treatment of a particular type of health disorder. Hence this classification is useful for doctors.
  • Analgesics: Pain killing effect
  • Antibiotics: To arrest the growth and kill bacteria
  • Antiseptics: To arrest the growth and kill bacteria
  • Tranquilizers: To reduce mental stress

Classification Based on the Action of Drugs:

  • These drugs are diseases oriented and have a different biological mode.
  • Examples: painkillers, antiarthritic, antihistamines medicines. All antihistamines inhibit the (stops) action of the compound histamine which produces allergic reaction such as inflammation in the body.

Classification Based on Chemical Structure:

  • This classification of drugs is based on the assumption that the drugs having similar chemical structure are expected to have similar pharmacological properties.
  • Examples: All sulphonamides having the similar type of chemical structure show antibacterial activity.


Classification Based on Molecular Targets:

  • Drugs interact with biomolecules like carbohydrates, proteins, lipids, nucleic acids etc. These are target molecules and the drugs are called target oriented drugs.
  • This classification is useful for medicinal chemists.
  • Examples: Many enzymes and receptors in cells have molecular targets.

Classification of Drugs by Lay Public:

  • This is not a scientific classification but commonly used by the lay public. This classification is based on the action of the drug and not on the chemistry of a drug or biological action of the drug.
  • Examples: Cough syrups, analgesics, laxatives, and purgatives.

Q2. Explain drug-enzyme interaction.

  • The enzymes are biological catalysts. They provide active sites which hold the substrate molecule in a suitable position so that it can be attacked by the reagent effectively. The substrate binds to amino acids of the protein present on active site through interactions like ionic bonding, hydrogen bonding, van der Waals’ interaction or dipole-dipole interaction.

Action of drugs 01

  • Enzyme provides functional groups that will attack the substrate and carry out a chemical reaction.
  • Drugs inhibit the action of enzymes. Such drugs are called enzyme inhibitors. Thus enzyme inhibitors block the binding site and prevent binding of substrate. They also inhibit the catalytic action of enzymes.

Drug – Enzyme Interaction:

  • Drugs inhibit the attachment of substrate on active site of enzymes in two ways.

Competitive inhibitor’s action:

  • Such inhibitors compete with the natural substrate for the active site. Hence such inhibitors are called competitive inhibitors.
  • In such cases, the drug occupies the position available for the substrate and thus prevent the substrate to occupy the active site on the enzyme. Thus the action of the enzyme is inhibited.

Action of drugs 02

Noncompetitive inhibitors action:

  • Some drugs do not bind to active site but bind to a different site of enzyme which is called allosteric site. Doing this it changes the shape of the active site.
  • Due to the change in the shape of the active site, the substrate can not recognize the active site. These inhibitors are called noncompetitive inhibitors.

Action of drugs 03

  • Note:
  • If the bond formed between the drug and the enzyme is strong covalent bond and can not be broken easily then the enzyme is blocked permanently. Then body degrades the blocked enzyme and synthesizes new enzyme.

Q3. Explain three physical methods for preservation of food.

By Removal of Heat (Cooling):

  • This method involves refrigeration, freezing, dehydro-freezing or carbonation.
  • At low temperature, the growth of the organism is inhibited. Cooling lowers the temperature of the substance which prevents the growth of the microorganisms
  • Fresh fruits, vegetables are preserved by this method.

By Addition of Heat:

  • This method involves pasteurization or sterilization. This process is also called canning or heat processing.
  • Heating kills microorganisms. Hence solid and liquid foods can be preserved by heating it.
  • Pasteurization is a sterilization process for preserving food by addition of heat or by increasing temperature. Pasteurization of milk is an example of this process.

By Removal of Water (Dehydration):

  • This process involves sun drying, freeze drying, and puff drying.
  • As water is removed the growth of the organisms is prevented.
  • Fishes, fruits, vegetables, and food grains are preserved by this method.

By Irradiation:

  • This method involves ultraviolet or ionizing radiation.
  • Irradiation controls the growth of microorganisms.
  • High energy electromagnetic radiation produces desired effects without inducing radioactivity in food.
  • Bakery products are preserved by this method.

Q4. Describe three chemical methods for preservation of food.

By Addition of Sugar:

  • In this method, sugar is added to the food which is to be preserved and is then heated.
  • This method is simple and cheap.
  • This method is used to preserve fruit jams, jellies, and marmalades.

By Addition of salt:

  • Salt is added during the preparation of the product.
  • Making pickles of raw mango, lemon, chilies, and preservation of fish products involve this method.

By Addition of Vinegar:

  • Dilute acetic acid commonly known as vinegar is added to food for preservation.
  • This method is used for preservation of pickles of raw mango, lemon, chilies salad dressing and preservation of fishes.

By Addition of Chemicals:

  • Sodium benzoate, salt o the ascorbic acid and propionic acid etc. are used as food preservatives. They inhibit the growth of microorganisms. These are added in small quantities to a food like jams, jellies, and juices.

Q5. State the uses of sulphur dioxide and sulphite as antioxidants.

  • The salts of sodium and potassium sulphite and bisulphites are used as antioxidants.
  • Sulphur dioxide is widely used as preservative and antioxidant in food and beverage industries.
  • Sulphites are used as antioxidants. They reduce discolorization of fruits, vegetables, and dehydrated potatoes.
  • Sulphites are used to preserve wine, dairy products, sauces, jams jellies etc.
  • They are used as food additives as antimicrobial agents, structure modifiers, enzyme inhibitors.

Q6. Explain the different types of detergents.

  • Detergents are sodium salts of long chain alkyl sulphates or a long chain of alkyl benzene sulphonate.
  • Synthetic detergents are mainly classified into three categories: Anionic detergents, Cationic detergents, and Non-ionic detergents

Anionic Detergents:

    • Anionic detergents are sodium salts of sulphonated long chain alcohols or hydrocarbons.
    • Example: Sodium n-dodecyl benzene sulphonate
    • Alkyl hydrogen sulphates formed by treating long chain alcohols with concentrated sulphuric acid and neutralized with alkali to form anionic detergents. Similarly, alkyl benzene sulphonates are obtained by neutralising alkyl benzene sulphonic acids with alkali.
  • In anionic detergents, the anionic part of the molecule is involved in the cleansing action. Sodium salts of alkyl benzene sulphonates are an important class of anionic detergents. They are mostly used for household work. Anionic detergents are also used in toothpaste.

Cationic Detergents:

  • Cationic detergents are quarternary ammonium salts of amines with acetates, chlorides or bromides as anions. Cationic part possesses a long hydrocarbon chain and a positive charge on the nitrogen atom. Hence, these are called cationic detergents.
  • Example: Cetyltrimethylammonium bromide. It is a popular cationic detergent and is used in hair conditioners.
  • Cationic detergents have germicidal properties and are expensive, therefore, these are of limited use.

Non-ionic Detergents:

  • Non-ionic detergents do not contain any ion in their constitution.
  • Example: Pentaerythrityl stearate
  • Liquid dishwashing detergents are a non-ionic type.
  • Mechanism of cleansing action of this type of detergents is the same as that of soaps. These also remove grease and oil by micelle formation.
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  1. Hi! The content is really helpful, but I'm unable to access the short answer(II) questions of chemistry in everyday life. Please make it available asap, thank you 🙂

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