CHAPTER 5

CHEMISTRY IN EVERYDAY LIFE

Syllabus

Chemicals in medicines: analgesics, tranquillizers, antiseptics, disinfectants, antimicrobials, antifertility drugs, antibiotics, antacids, antihistamines.

Chemicals in food – preservatives, artificial sweetening agents, elementary idea of antioxidants.

Cleansing agents – soaps and detergents, cleansing action.

Chapter Analysis

2016 2017 2018

List of Topics D OD OD D/OD

Definitions 1Q 1Q

(3 marks) (3 marks)

Soap 1Q

(3 marks)*

Antiseptics 1Q

(3 marks)*

Food Preservatives 1Q

(3 marks)*

• One question of 3 marks with one question each of 1 mark on Soap, Tincture of Iodine and Food Preservative was asked.

On the basis of above analysis it can be said that from exam point of view, Soap, Antiseptics and Food Preservatives and definitions of various drugs with their examples are the most important topics of the chapter.

Revision Notes

➣ Drugs: Drugs are the chemical substances of low molecular mass, interacting with macromolecular targets and produce a biological response.

➣ Medicines: Drugs which produce a therapeutic and useful response.

➣ Chemotherapy: It is the science in which chemicals are used in the treatment of diseases due to bacterial invasion. These chemicals destroy the microorganisms without affecting any material extent (the tissues of the host).

➣ Classification of Drugs:

1. On the basis of pharmacological effect: Most useful for doctors as it provides the whole range of drugs available for the treatment of a particular type of problem. e.g., analgesics have pain killing effect, antiseptics kill or arrest the growth of microorganisms.

1. On the basis of drug action: It is based on the action of a drug on a particular biochemical process. e.g., all histamines inhibit the action of the compound histamines, which causes inflammation of the body.
2. On the basis of chemical structure: Drugs which have common structural features and often have similar pharmacological activity. e.g., sulphonamides have common structural feature.

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344 Oswaal CBSE Chapterwise & Topicwise Question Bank, CHEMISTRY, Class – XII

1. On the basis of molecular targets: Drugs generally interact with biological macromolecules such as carbohydrates, proteins, lipids and nucleic acids called target molecules. This classification is based upon the type of the molecular target with which the drug interacts.

➣ Enzymes are the proteins which perform the role of biological catalysts in the body. Carrier proteins carry polar molecules across the cell membrane.

➣ Catalytic action of enzymes:

1. The prime 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, such that it can be attacked by the reagents effectively. Substrates bind to the active site of the enzymes through many kinds of interactions like ionic bonding, hydrogen bonding, van der Waals or dipole-dipole interactions.

1. The second function of an enzymes is to provide functional groups that will attack the substrate and carry out chemical reaction.

Active site (a) <math display="block">Fig.\ 1: (a)\ Active\ site\ of\ an\ enzyme, (b)\ Substrate, (c)\ Enzyme\ holding\ the\ substrate</math>

➣ Drug-enzyme interactions: Drugs can block the binding site of the enzyme and prevent the binding of substrate, or can inhibit the catalytic activity of the enzyme. Such drugs are called enzyme inhibitors. Drugs inhibit the attachment of substrate on active site of enzymes in two ways:

Drugs compete with natural substrate for their attachment on the active sites of enzymes. Such drugs are called competitive inhibitors. <math>\langle \cdot \rangle</math>

Active site _Drug- Drug

Enzyme Substrate Enzyme Substrate

Drug and substrate competing Drug blocks the active

for active site of enzyme site of enzyme

Fig. 2: Drug and substrate competing for active site

1. Instead of joining to the enzyme's active site, some drugs bind to a different site of enzyme which is called allosteric site. This can change the shape of the active site in such a way that the substrate can't recognize 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 synthesises the new enzyme.

Active site with

Active site changed shape

Enzyme Allosteric site Inhibitor occupying

← Inhibitor allosteric site

Fig. 3: Non-competitive inhibitor changes the active site of enzyme after binding all allosteric site