Chemistry IN Every DAY Life flash cards

1. 1.What are drugs in the chemical/pharmacological sense?

   Drugs are chemicals of low molecular mass ($\sim 100$ to $500\ u$) that interact with macromolecular targets and produce a biological response; when the response is therapeutic and useful they are used in medicines (chemotherapy).

   Hint: Low MW chemicals producing a biological response.

2. 2.Define chemotherapy.

   The use of chemicals (drugs) for the treatment of diseases.

   Hint: Chemicals + therapy.

3. 3.Why must the drug dose be carefully controlled?

   Because most drugs are toxic; they are useful (medicines) only in appropriate small doses, and higher doses can be harmful or poisonous.

   Hint: Right amount = medicine; excess = poison.

4. 4.List the four common bases for classification of drugs.

   (i) On pharmacological effect, (ii) on the drug action (mechanism at target), (iii) on the chemical structure, (iv) on the molecular target it acts on.

   Hint: Effect, action, structure, target.

5. 5.Classification of drugs on the basis of pharmacological effect — what does it give and who uses it?

   It groups drugs by the biological effect they produce (e.g. all analgesics reduce pain, all antiseptics kill microbes). It is useful for doctors because it provides the whole range of drugs available for a given type of problem.

   Hint: Useful for the doctor.

6. 6.Classification on the basis of drug action is based on what?

   On the action of the drug on a particular biochemical process (e.g. antihistamines inhibit the action of the compound histamine).

   Hint: Which biochemical process it blocks.

7. 7.Classification on the basis of chemical structure groups drugs how?

   Drugs with a common structural feature (and often similar pharmacological activity) are put together, e.g. the sulpha drugs (sulphonamides).

   Hint: Shared structural skeleton.

8. 8.Classification on the basis of molecular target is the most useful for whom, and why?

   Most useful for medicinal chemists, because it correlates the drug with its biomolecular target and helps in rational drug design.

   Hint: Useful for the chemist designing drugs.

9. 9.What are the main macromolecular targets (drug targets) in the body?

   Proteins such as enzymes, receptors, carrier proteins, and nucleic acids (as in genetic material) — these are the biomolecules on which drugs act.

   Hint: Enzymes, receptors, carrier proteins, nucleic acids.

10. 10.What is the active site of an enzyme, and how do drugs interfere with it?

    The active site is the region where the substrate binds and the reaction is catalysed. Drugs can block this site (compete with the substrate) so the substrate cannot bind, or bind elsewhere to change the enzyme's shape.

    Hint: Where the substrate normally binds.

11. 11.Distinguish a competitive inhibitor from a non-competitive (allosteric) inhibitor of an enzyme.

    A competitive inhibitor resembles the substrate and competes for the same active site. A non-competitive inhibitor binds at a different (allosteric) site, changing the shape of the active site so the substrate no longer fits.

    Hint: Same site (competes) vs different site (allosteric).

12. 12.How do enzyme inhibitors generally work as drugs?

    They inhibit an enzyme's catalytic activity by blocking the active site (competitive) or by binding to an allosteric site and distorting the active site, thereby preventing the substrate from binding.

    Hint: Block the active site or distort it.

13. 13.What decides whether the binding of a drug to an enzyme's active site is reversible or irreversible?

    If the drug binds through weak forces (H-bonds, van der Waals, ionic) the inhibition is reversible; if it binds by strong covalent bonds the enzyme is permanently blocked (irreversible inhibition).

    Hint: Weak bonds = reversible; covalent = permanent.

14. 14.What are receptors as drug targets?

    Receptors are proteins (mostly embedded in cell membranes) that receive chemical messengers and transmit the message into the cell, triggering a biological response.

    Hint: Proteins that receive chemical messengers.

15. 15.How does chemical communication between neurons/across a receptor occur?

    A chemical messenger (e.g. a neurotransmitter) is released from one cell, crosses the gap, and binds to the receptor site of the next cell — its shape/structure fitting the receptor — opening a message pathway.

    Hint: Messenger binds the receptor's binding site.

16. 16.Define agonist drugs.

    Drugs that mimic the natural chemical messenger by binding to the receptor and switching on its response; they are useful when the natural messenger is deficient.

    Hint: Mimic the natural messenger (switch ON).

17. 17.Define antagonist drugs.

    Drugs that bind to the receptor site and block (inhibit) its natural function, preventing the natural messenger from acting; useful when the natural message needs to be stopped.

    Hint: Block the receptor (switch OFF).

18. 18.Why is the exact three-dimensional shape of a drug so important for its action?

    Because drugs must fit their target (active site or receptor) like a key in a lock; only a molecule with the right shape and functional groups binds and produces the response.

    Hint: Lock-and-key fit.

19. 19.What are antacids?

    Substances that neutralise excess acid in the stomach (raise the pH to an appropriate level) and thereby relieve hyperacidity, pain and irritation.

    Hint: Neutralise excess stomach HCl.

20. 20.Give examples of simple (weak-base) antacids.

    Sodium hydrogen carbonate (baking soda), magnesium hydroxide (milk of magnesia), aluminium hydroxide, magnesium carbonate — mild bases that neutralise acid.

    Hint: Baking soda, milk of magnesia, Al(OH)3.

21. 21.What is the drawback of using $NaHCO_3$ as an antacid?

    Excess sodium hydrogen carbonate can make the stomach alkaline, which triggers the production of even more acid (rebound acidity); metal hydroxides are better as they do not overshoot.

    Hint: Can make stomach too alkaline → more acid.

22. 22.Why were antacids that only neutralise acid found inadequate for ulcers, and what replaced them?

    They only treat the symptom (excess acid) not the cause. The breakthrough was drugs that prevent excess acid formation by acting on the receptor that triggers acid release, e.g. cimetidine (Tagamet) and ranitidine (Zantac).

    Hint: Cimetidine and ranitidine — control acid release.

23. 23.How do cimetidine and ranitidine reduce acid, and what class are they?

    They are histamine ($H_2$) receptor antagonists: they prevent histamine from binding to the receptors in the stomach wall that stimulate secretion of hydrochloric acid, so less acid is produced.

    Hint: Block histamine H2 receptors in the stomach.

24. 24.A newer approach to hyperacidity uses proton pump inhibitors like omeprazole. What do they do?

    They inhibit the enzyme (proton pump / $H^+/K^+$ ATPase) that pumps $H^+$ into the stomach, thereby switching off acid production at the final step.

    Hint: Inhibit the acid-pumping enzyme.

25. 25.What is histamine and what does it do in the body?

    Histamine is a potent vasodilator released in the body that contracts smooth muscle in the bronchi and gut, dilates capillaries, and causes the symptoms of allergy, nasal congestion and inflammation.

    Hint: Mediator of allergy and inflammation.

26. 26.What are antihistamines, and how do they work?

    Antihistamines (antiallergic drugs) interfere with the natural action of histamine by competing with it for the binding sites of the $H_1$ receptor, thereby preventing allergic symptoms.

    Hint: Compete with histamine for its receptor.

27. 27.Give common examples of antihistamine drugs.

    Brompheniramine (Dimetapp), terfenadine (Seldane), diphenhydramine, and cetirizine.

    Hint: Brompheniramine, terfenadine.

28. 28.Antihistamines relieve allergy but do not reduce stomach acid, while cimetidine reduces acid but not allergy. Why?

    Because they act on different receptors: antihistamines block the $H_1$ receptors (allergy), while cimetidine/ranitidine block the $H_2$ receptors in the stomach (acid). The same messenger (histamine) works through different receptors in different tissues.

    Hint: H1 receptors (allergy) vs H2 receptors (acid).

29. 29.What are neurologically active drugs / tranquilizers?

    Tranquilizers are a class of chemicals used to treat stress, mild and severe mental diseases; they relieve anxiety, stress, irritability and excitement and are an essential component of sleeping pills.

    Hint: Reduce anxiety/stress; part of sleeping pills.

30. 30.How do many tranquilizers act on the brain chemically?

    They affect the message-transfer mechanism from nerve to receptor — many act by influencing neurotransmitters (e.g. inhibiting enzymes that degrade noradrenaline, or enhancing the calming neurotransmitter), inducing a feeling of well-being.

    Hint: Alter neurotransmitter action in the brain.

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