CBSE Class 12 Chemistry Chapter 16: Chemistry in Everyday Life NCERT Solutions

Classifying drugs is essential for several reasons, providing different perspectives that are useful for various medical professionals and researchers:

1. On the basis of pharmacological effect: This classification helps doctors by presenting a comprehensive range of drugs available to treat a specific medical condition. It aids in selecting the most effective treatment option.
2. On the basis of drug action: This method categorizes drugs based on how they affect particular biochemical processes within the body. Understanding the specific action is crucial for predicting outcomes and side effects.
3. On the basis of chemical structure: Grouping drugs by their chemical structure reveals similarities in their molecular makeup. Drugs with similar structures often exhibit similar pharmacological activities, which can guide the development of new drugs.
4. On the basis of molecular targets: This classification is particularly valuable for medicinal chemists. It groups drugs that act on the same molecular targets (like specific enzymes or receptors) through similar mechanisms of action, facilitating drug design and understanding of biological pathways.

In medicinal chemistry, drug targets refer to specific molecules within the body, usually macromolecules, that play a critical role in the progression of a disease. These targets are often essential components of metabolic pathways that, when disrupted, lead to specific pathological conditions.

Common examples of drug targets include proteins (like enzymes and receptors), carbohydrates, lipids, and nucleic acids. Medicinal chemists design drugs as chemical agents that can selectively bind to these target molecules. By binding to the active sites or specific regions of these targets, drugs can either inhibit or enhance their function, thereby modulating the biochemical processes involved in the disease and producing a therapeutic effect.

The primary macromolecules that are commonly chosen as drug targets in medicinal chemistry are:

• Carbohydrates
• Lipids
• Proteins
• Nucleic acids

These molecules are fundamental to cellular function and are often implicated in disease processes, making them ideal sites for drug intervention.

Medicines should not be taken without consulting a doctor due to the following critical reasons:

• Multiple Receptor Interactions: A single drug molecule can often bind to more than one type of receptor site in the body. While it might be designed to interact with a specific target for therapeutic benefit, it could also bind to other sites, potentially causing unintended and harmful effects (toxicity).
• Dose-Dependent Toxicity: Most medicines are effective and safe only within a specific dosage range. Taking higher doses than recommended can lead to severe adverse effects, turning a beneficial drug into a poison.

Therefore, a doctor's expertise is necessary to determine the correct medication, appropriate dosage, and duration of treatment, ensuring efficacy while minimizing risks.

Chemotherapy is defined as the use of chemical substances for the purpose of achieving a therapeutic effect. This broad definition encompasses the application of chemicals in the diagnosis, prevention, and treatment of diseases. It is a cornerstone of modern medicine, particularly in areas like cancer treatment and infectious diseases.

Drugs bind to the active sites of enzymes through various types of intermolecular forces. These forces are crucial for the drug's ability to interact with and modulate the enzyme's activity. The forces commonly involved are:

1. Ionic bonding: Occurs between oppositely charged groups on the drug and the enzyme.
2. Hydrogen bonding: Involves the attraction between a hydrogen atom bonded to a highly electronegative atom (like O or N) and another electronegative atom nearby.
3. Dipole–dipole interaction: Arises from the attraction between the positive end of one polar molecule and the negative end of another.
4. van der Waals forces: These are weak, short-range electrostatic forces that occur between all molecules, including nonpolar ones, due to temporary fluctuations in electron distribution.

Antacids and antiallergic drugs do not interfere with each other's function because they target different types of receptors or molecules, even though both might be related to histamine's effects in some way.

Antacids work by neutralizing the excess acid in the stomach, primarily targeting the parietal cells' proton pumps or directly reacting with hydrochloric acid. They do not significantly interact with histamine receptors involved in allergic responses.

Antiallergic drugs, such as antihistamines, specifically block histamine receptors (like H1 receptors) that are involved in triggering allergic reactions. While histamine can also stimulate acid secretion in the stomach (acting on H2 receptors), modern antiallergic drugs are designed to be selective for the H1 receptors responsible for allergy symptoms. Therefore, antacids, which focus on stomach acid neutralization, and antiallergic drugs, which block H1 receptors, operate on distinct biological mechanisms and target sites, preventing interference with each other's primary functions.