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Q1.   The most useful classification of drugs for medicinal chemist is  

• 1) On the basis of pharmacological effect
• 2) On the basis of drug action
• 3) On the basis of chemical structure
• 4) On the basis of molecular targets

Solution

The most useful classification of drugs for medicinal chemist is on the basis of molecular targets.

Q2. Which class of drugs share common structural features and often have similar pharmacological activity?

• 1) Caffine
• 2) Sulphonamides
• 3) Paracetamol
• 4) Aspirin

Solution

Sulphonamides are the drugs which share common structural features and often have similar pharmacological activity.

Q3. Why are cleansing agents such as detergents preferred over soap?

Solution

Detergents are cleansing agents which have all the properties of soaps, but which actually do not contain any soap. Detergents are preferred over soap as it works on hard water i.e. it forms foam in both hard and soft water, unlike soap. Some of the detergents give foam even in ice cold water.

Q4. Explain Drug-enzyme interaction.

Solution

Drug-enzyme interactionDrugs inhibit any of the above mentioned activities of enzymes. These 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 different ways;(i) Drugs compete with the natural substrate for their attachment on the active sites of enzymes. Such drugs are called competitive inhibitors. (ii) 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 binding of inhibitor at allosteric site changes the shape of the active site in such a way that substrate cannot recognise 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.

Q5. Explain the role of receptors as drug target? How the receptor receives the chemical messenger?

Solution

Receptors are proteins that are crucial to body's communication process. Majority of these are embedded in cell membranes.Message between two neurons and that between neurons to muscles, in the body is communicated through certain chemicals known as chemical messengers. These are received at the binding sites of the receptor proteins. Shape of the receptor site changes when it accommodates a messenger so as to ease the transfer of message to the cell. Thus even without entering the cell the chemical messenger passes the message.Based on the shape, structure and amino acid composition of the binding site, the receptors shows selectivity for the chemical messengers. Hence different receptors in the body interact with different chemical receptors.

Q6. What are Antagonists and Agonists in drug action?

Solution

Antagonists are the drugs that binds to the receptor site to inhibit its function and are useful when blocking of message is required. Agonists are the drugs that mimic the natural messenger by switching on the receptor and are useful when there is lack of natural chemical messenger.

Q7. Write a note on catalytic action of enzymes.

Solution

Catalytic action of enzymesFor understanding the interaction between a drug and an enzyme, it is important to know how do enzymes catalyse the reaction. In their catalytic activity, enzymes perform two major functions:1. The first 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, so that it can be attacked by the reagent effectively. Substrates bind to the active site of the enzyme through a variety of interactions such as ionic bonding, hydrogen bonding, van der Waals interaction or dipole-dipole interaction. 2. The second function of an enzyme is to provide functional groups that will attack the substrate and carry out chemical reaction.

Q8. Give an example of artificial sweetening agent?

Solution

Aspartame, Saccharin, Sucralose, Alitame etc. are artificial sweetening agent.

Q9. Write a brief note on classification of drugs.

Solution

Drugs can be classified mainly on criteria outlined as follows:(a) On the basis of pharmacological effectThis classification is based on pharmacological effect of the drugs. It is useful for doctors because it provides them the whole range of drugs available for the treatment of a particular type of problem. For example, analgesics have pain killing effect, antiseptics kill or arrest the growth of microorganisms.(b) On the basis of drug actionIt is based on the action of a drug on a particular biochemical process. For example, all antihistamines inhibit the action of the compound, histamine which causes inflammation in the body. There are various ways in which action of histamines can be blocked. (c) On the basis of chemical structureIt is based on the chemical structure of the drug. Drugs classified in this way share common structural features and often have similar pharmacological activity. For example, sulphonamides have common structural feature, given below. Structural Features of Sulphonamides(d) On the basis of molecular targetsDrugs usually interact with biomolecules such as carbohydrates, lipids, proteins and nucleic acids. These are called target molecules or drug targets. Drugs possessing some common structural features may have the same mechanism of action on targets. The classification based on molecular targets is the most useful classification for medicinal chemists.

Q10. What are cationic detergents? Which cationic detergent is used in hair conditioner?

Solution

Cationic detergents are quarternary ammonium salts of amines with acetates, chlorides or bromides as anions. Cationic part possess a long hydrocarbon chain and a positive charge on nitrogen atom. Hence, these are called cationic  detergents. Cetyltrimethylammonium bromide is a popular cationic detergent and is used in hair conditioners.

Q11. What are non-ionic detergents?

Solution

Detergents which does not contain any ion in their constitution are non-ionic detergents. Example of such a detergent is formed when Stearic acid reacts with Polyethylene glycol. Liquid dishwashing detergents are non-ionic type.

Q12. What is the need of artificial-sweetening agents?

Solution

Artificial sweetening agents are useful to diabetic person and to people who need to control intake of calories.