Chemistry in Everyday Life Class 12 Chapter Notes

Key Definitions

Drugs (Medicines)

Chemical substances of low molecular mass (<500 amu) that interact with macromolecular targets and produce a biological response, used for diagnosis, prevention, or cure of diseases.

Chemotherapy

The use of chemicals for therapeutic effect, i.e., treatment of diseases.

Drug Target

Biological macromolecules (like proteins, nucleic acids, lipids, carbohydrates) in the body that drugs bind to and interact with to produce a therapeutic effect.

Antacids

Chemical substances that neutralize excess acid in the stomach and raise the pH to an appropriate level, relieving acidity and heartburn.

Antihistamines

Drugs that inhibit the action of histamine, a chemical responsible for allergic reactions (e.g., cold, hay fever) and also stimulates the secretion of pepsin and HCl in the stomach.

Analgesics

Drugs that reduce or abolish pain without causing impairment of consciousness, mental confusion, incoordination, or paralysis.

Antiseptics

Chemicals applied to living tissues (skin, wounds, mucous membranes) to prevent the growth of microorganisms or to kill them.

Disinfectants

Chemicals applied to inanimate objects (floors, instruments, sewage systems) to kill microorganisms but are harmful to living tissues.

Artificial Sweeteners

Chemical substances that sweeten food but add minimal or no calories, used as sugar substitutes for diabetics and calorie-conscious individuals.

Drugs and Their Classification

Drugs are potent chemical substances designed to elicit a specific biological response within the body. Their effectiveness hinges on their ability to interact with specific macromolecular targets, which are typically proteins (like enzymes or receptors), nucleic acids, or lipids. The classification of drugs is crucial for understanding their action and application.

Drugs can be broadly classified based on several criteria:

1. On the basis of Pharmacological Effect: This classification is based on the therapeutic action of the drug. For example, analgesics reduce pain, antiseptics kill or prevent the growth of microorganisms, and antihistamines block the action of histamine. This is useful for doctors as it tells them what a drug does for a particular ailment.

1. On the basis of Drug Action: This classification is based on the action of a drug on a particular biochemical process. For instance, drugs that inhibit the action of histamine (antihistamines) act on specific histamine receptors. This is more specific than pharmacological effect and helps understand how the drug works at a molecular level.

1. On the basis of Chemical Structure: Drugs that share similar structural features often have similar pharmacological activities. For example, sulphonamides are a class of antibiotics that all contain the sulphonamide functional group. This is useful for medicinal chemists to design new drugs with similar properties.

1. On the basis of Molecular Targets: This is the most fundamental classification. Drugs primarily interact with biological macromolecules such as enzymes and receptors.

• Enzymes act as catalysts in biochemical reactions. Drugs can inhibit enzyme activity (enzyme inhibitors) by blocking the active site or by binding to an allosteric site, altering the enzyme's shape. This prevents the substrate from binding or the reaction from occurring.
• Receptors are proteins that are crucial for communication systems in the body. They are usually embedded in the cell membrane. Drugs bind to these receptor sites to either mimic the natural messenger (agonists) or block the messenger's binding (antagonists), thereby initiating or inhibiting a cellular response. Understanding these molecular interactions is key to modern drug design and development.

Types of Therapeutic Drugs

Key Points to Remember

• Antacids vs. Antihistamines: Cimetidine and Ranitidine are technically antihistamines that block the interaction of histamine with receptors in the stomach wall, reducing acid production. Simple antacids like Mg(OH)₂ or Al(OH)₃ only neutralize existing acid.
• Antiseptics vs. Disinfectants: Antiseptics (e.g., Dettol, Savlon) are safe for living tissues; disinfectants (e.g., 1% phenol solution, chlorine in high conc.) are for inanimate objects.
• Broad-spectrum vs. Narrow-spectrum Antibiotics: Broad-spectrum (e.g., Chloramphenicol, Ampicillin) kill or inhibit a wide range of Gram-positive and Gram-negative bacteria. Narrow-spectrum (e.g., Penicillin G) are effective against a limited range.
• Narcotic vs. Non-narcotic Analgesics: Non-narcotic (e.g., Aspirin, Paracetamol) are non-addictive and reduce fever. Narcotic (e.g., Morphine, Codeine) are addictive, used for severe pain, and produce sleep/unconsciousness.
• Artificial Sweeteners: Saccharin, Aspartame, Sucralose, Alitame. Aspartame is unstable at cooking temperatures. Sucralose is stable at high temperatures.
• Food Preservatives: Prevent food spoilage due to microbial growth. Examples: Sodium benzoate, Sodium metabisulphite, common salt, sugar, vegetable oil.
• Soaps vs. Synthetic Detergents: Soaps are sodium/potassium salts of long-chain fatty acids. Detergents are superior, work in hard water, and are derived from hydrocarbons. They can be anionic, cationic, or non-ionic.
• Biodegradable vs. Non-biodegradable Detergents: Biodegradable detergents have straight hydrocarbon chains that can be easily decomposed by bacteria. Non-biodegradable ones have branched chains, causing environmental pollution.

Section 5

For this chapter, focus on memorizing specific drug names and their classifications. Pay close attention to distinguishing similar terms like antiseptics vs. disinfectants, and broad-spectrum vs. narrow-spectrum antibiotics. Questions often test your ability to correctly identify the category a given drug belongs to or to provide examples for a specific therapeutic class. Create a table for revision with Drug Name, Class, and Key Function/Application. Understand the basic working principle (e.g., how an antacid works, or how an artificial sweetener provides sweetness without calories). Structure-activity relationship is generally not deeply tested, but knowing functional groups associated with certain drug classes can be helpful.

Practice Questions with Solutions

• Q: Give one example each of an antiseptic and a disinfectant. Can phenol act as both? A: Antiseptic: Dettol (chloroxylenol + terpineol). Disinfectant: 1% solution of phenol. Yes, phenol can act as both: 0.2% solution is an antiseptic, while 1% solution is a disinfectant.
• Q: Why is aspartame not used in baking or cooking? A: Aspartame is unstable at cooking temperatures and decomposes, losing its sweetness. Sucralose is a better choice for high-temperature applications.
• Q: Name two broad-spectrum antibiotics and explain their significance. A: Chloramphenicol and Ampicillin. Their significance lies in their effectiveness against a wide range of both Gram-positive and Gram-negative bacteria, making them useful when the exact bacterial pathogen is not immediately known.
• Q: How do tranquilizers differ from analgesics in their primary function? A: Tranquilizers primarily reduce anxiety, stress, and mental tension, inducing a sense of well-being. Analgesics primarily relieve pain without affecting consciousness or mental state.

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