B.Pharmacy 6th Semester Medicinal Chemistry-III Important Question Answer
B.Pharmacy 6th Semester Medicinal Chemistry Important Question Answer
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Medicinal Chemistry-III Very Short Answer [2 Marks]
1. Define Sulphonamides.
Answer:
Sulphonamides are synthetic antimicrobial agents that contain the sulfonamide group (-SO₂NH₂). They act by inhibiting bacterial synthesis of folic acid.
General structure:
2. What is bioisosterism?
Answer:
Bioisosterism is the replacement of an atom or group in a drug molecule with another that has similar physical or chemical properties, without affecting its biological activity. This is used to improve potency, reduce toxicity, or enhance pharmacokinetics.
3. Name any two drugs used in the treatment of tuberculosis.
Answer:
Isoniazid
Rifampicin
These are first-line antitubercular agents used in combination therapy.
4. Write uses of Chloroquine.
Answer:
Chloroquine is used for the prevention and treatment of malaria. It is also used in the treatment of autoimmune diseases like rheumatoid arthritis and lupus erythematosus.
5. Define Antiseptics.
Answer:
Antiseptics are chemical substances that inhibit the growth of or kill microorganisms on living tissues (like skin, wounds) without harming them. Examples include iodine and chlorhexidine.
6. Define term Antibiotic, bactericidal and bacteriostatic.
Answer:
Antibiotic: A substance produced by microorganisms that inhibits or kills other microbes.
Bactericidal: Kills bacteria (e.g., penicillin).
Bacteriostatic: Inhibits bacterial growth (e.g., tetracycline).
7. Write mechanism of action of Tetracyclines.
Answer:
Tetracyclines inhibit bacterial protein synthesis by binding to the 30S ribosomal subunit, preventing the attachment of aminoacyl-tRNA to the mRNA-ribosome complex.
8. What are monoclonals? Name one recombinant antibiotic.
Answer:
Monoclonal antibodies (mAbs) are identical antibodies produced from a single B-cell clone, designed to bind to specific antigens.
Example of recombinant antibiotic: Interferon-alpha.
9. Give mechanism of action of Ciprofloxacin.
Answer:
Ciprofloxacin inhibits bacterial DNA gyrase and topoisomerase IV, enzymes essential for DNA replication, transcription, and repair, leading to bacterial death.
10. Give mechanism of action of Amphotericin B.
Answer:
Amphotericin B binds to ergosterol in fungal cell membranes, creating pores that increase permeability, leading to leakage of cellular contents and cell death.
11. Outline synthesis of Dapsone.
Answer:
Synthesis of Dapsone involves:
Nitration of benzene to form 1,4-dinitrobenzene.
Reduction of nitro groups to amines forming 4,4'-diaminodiphenylsulfone (Dapsone).
Structure of Dapsone:
12. What is Pharmacophore?
Answer:
A pharmacophore is the abstract arrangement of atoms or groups in a molecule essential for biological activity. It includes features like hydrogen bond donors/acceptors, aromatic rings, and hydrophobic centers that interact with a biological target.
13. Outline synthesis of Metronidazole.
Answer:
Synthesis Steps:
Nitration of imidazole ring.
Alkylation with ethylene oxide or chloropropanol.
Final compound is Metronidazole.
Structure of Metronidazole:
14. Write mechanism of action of Sulphonamides.
Answer:
Sulphonamides inhibit dihydropteroate synthase, blocking the conversion of PABA to dihydrofolic acid in bacteria, thereby halting DNA synthesis.
15. What is Docking?
Answer:
Docking is a computer-based technique in drug design that predicts the preferred orientation of a drug (ligand) when bound to a protein (target) to form a stable complex.
16. Give the structure and mechanism of Miconazole.
Answer:
Structure of Miconazole:
Mechanism:
Miconazole inhibits fungal lanosterol 14-α-demethylase, impairing ergosterol synthesis and compromising membrane integrity.
17. Give the structure and mechanism of Ampicillin.
Answer:
Structure of Ampicillin:
Mechanism:
Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis.
18. Synthesis of Primaquine.
Answer:
Primaquine is synthesized by:
Condensation of 8-aminoquinoline with appropriate side chain (e.g., 2-methoxy-3-methylbutylamine).
Purification and isolation.
Structure of Primaquine:
19. Give the structure and mechanism of Azithromycin.
Answer:
Structure of Azithromycin:
Mechanism:
Binds to the 50S ribosomal subunit, inhibiting bacterial protein synthesis.
20. Synthesis of Isoniazid.
Answer:
Reaction of isonicotinic acid with hydrazine hydrate.
Produces isonicotinic acid hydrazide (Isoniazid).
Structure of Isoniazid:
21. Give the structure and mechanism of Albendazole.
Structure:
Mechanism:
Albendazole binds to β-tubulin of parasites, inhibiting microtubule polymerization and glucose uptake, leading to energy depletion and death.
22. Give the structure and uses of Dapsone.
Structure:
Uses:
Used in the treatment of leprosy, dermatitis herpetiformis, and as a prophylactic agent in HIV-related infections.
23. Give the structure and mechanism of Mebendazole.
Structure:
Mechanism:
Inhibits microtubule synthesis in intestinal helminths, disrupting glucose uptake and causing death.
24. What do you mean by solid phase synthesis?
Answer:
Solid phase synthesis involves anchoring a starting molecule to a solid resin. Reagents are added sequentially, allowing easy purification by washing. Used commonly for peptides and oligonucleotides.
25. Enlist the approaches of drug design.
Answer:
Ligand-based drug design
Structure-based drug design
De novo drug design
Computer-aided drug design (CADD)
26. Write the mechanism of action of Tetracyclines.
Answer:
Tetracyclines bind to the 30S ribosomal subunit, preventing aminoacyl-tRNA attachment, thus inhibiting protein synthesis in bacteria.
27. Draw a structure of benzyl penicillin.
Structure:
28. Write the mechanism of action of Isoniazid.
Answer:
Isoniazid inhibits mycolic acid synthesis by blocking the enzyme InhA, essential for mycobacterial cell wall formation.
29. Halides used as an antiseptic agent.
Answer:
Iodine (as tincture, povidone-iodine)
Chlorine (in hypochlorite solutions)
Used for disinfection of skin, wounds, and water.
30. Mention the name of any two antibiotics.
Answer:
Penicillin
Streptomycin
Both are naturally derived antibiotics effective against various bacterial infections.
31. Outline the synthesis of any one antitubercular drug.
Example: Isoniazid
Isonicotinic acid reacts with hydrazine hydrate.
Forms isonicotinic acid hydrazide (Isoniazid).
Structure:
32. Cyclopentanol comes under which heterocyclic moiety in structure?
Answer:
Cyclopentanol is not a heterocyclic compound itself but may appear as a substituent in heterocyclic compounds. It contains a five-membered carbocyclic ring with a hydroxyl group.
33. Give any two examples of antineoplastic agents.
Answer:
Cyclophosphamide
Doxorubicin
These are used in the treatment of various cancers.
34. Write the biological source of Streptomycin.
Answer:
Streptomycin is obtained from Streptomyces griseus, a species of actinobacteria.
35. Name any two software used for molecular modeling and docking studies.
Answer:
AutoDock
MOE (Molecular Operating Environment)
Both are widely used in structure-based drug design.
36. Name any two β-Lactamase inhibitors.
Answer:
Clavulanic acid
Sulbactam
These are combined with β-lactam antibiotics to overcome resistance.
37. Give the degradation products of Penicillin.
Answer:
Penicilloic acid (via hydrolysis of β-lactam ring)
Penilloic acid (from further degradation)
These are inactive and allergenic.
38. Discuss mechanism of action of sulphonamides.
Answer:
Sulphonamides act by competitively inhibiting the enzyme dihydropteroate synthase, blocking PABA utilization in folic acid synthesis, leading to inhibition of bacterial DNA replication.
39. What is lead compound?
Answer:
A lead compound is a chemical structure that exhibits pharmacological activity and serves as a starting point for further modification to develop a drug candidate.
40. Write the synthesis of Isoniazid.
Same as Q31
React isonicotinic acid with hydrazine hydrate → Isoniazid.
41. Give the structure of Chloroquine.
Structure:
42. Give the structures of derivatives of Artemisinin.
Examples:
Artemether
Artesunate
Artemether Structure:
Artesunate Structure:
43. Elaborate Cotrimoxazole.
Answer:
Cotrimoxazole is a combination of sulfamethoxazole and trimethoprim in a 5:1 ratio.
Sulfamethoxazole inhibits dihydropteroate synthase.
Trimethoprim inhibits dihydrofolate reductase.
Together, they block bacterial folic acid synthesis synergistically.
44. Name any two antibiotics used as anti-tubercular.
Answer:
Rifampicin
Streptomycin
Used in combination therapy for TB.
45. Give the structure and mechanism of action of Acyclovir.
Structure:
Mechanism:
Acyclovir is converted to its triphosphate form, which inhibits viral DNA polymerase and incorporates into viral DNA, causing chain termination.
46. Falls under the drug category of antibacterial agents.
Example Answer:
Ciprofloxacin (Fluoroquinolone class)
Ampicillin (β-lactam antibiotic)
Both are antibacterial agents effective against bacterial infections.
47. Give etiology of malaria.
Answer:
Malaria is caused by Plasmodium species (P. falciparum, P. vivax, P. malariae, P. ovale), transmitted through the bite of female Anopheles mosquitoes.
48. Name any four drugs under the category of Tetracyclines.
Answer:
Tetracycline
Doxycycline
Minocycline
Oxytetracycline
All are broad-spectrum antibiotics.
49. Define folate reductase inhibitors with examples.
Answer:
Folate reductase inhibitors block dihydrofolate reductase, preventing the formation of tetrahydrofolate, essential for DNA synthesis.
Examples: Trimethoprim, Pyrimethamine.
50. Why is formalin packed in antibacterial caps?
Answer:
Formalin (aqueous formaldehyde) is packed in antibacterial caps to prevent microbial contamination and maintain its sterilizing activity, as it is prone to polymerization and degradation.
51. Name any four drugs belonging to N₄ and N₁ substituted sulphonamides.
Answer:
N₁-substituted:
Sulfisoxazole
Sulfamethizole
N₄-substituted:
3. Sulfadiazine
4. Sulfamethoxazole
These substitutions affect solubility and activity.
52. Define Antiprotozoal agents with examples.
Answer:
Antiprotozoal agents are drugs that kill or inhibit protozoa, the causative organisms of diseases like malaria and amoebiasis.
Examples:
Metronidazole
Chloroquine
53. Write synthesis of Proguanil.
Answer:
React 4-chlorophenyl biguanide with isopropyl isocyanate.
Final product: Proguanil (a prodrug of cycloguanil).
Structure of Proguanil:
54. Enlist the drugs used as Anthelmintics.
Answer:
Albendazole
Mebendazole
Ivermectin
Pyrantel pamoate
Used to treat worm infestations.
55. Write down the synthetic procedure for Nitrofurantoin.
Answer:
React 5-nitrofuraldehyde with semicarbazide to form intermediate.
Cyclize to form Nitrofurantoin.
Structure of Nitrofurantoin:
56. What is Chromophore?
Answer:
A chromophore is a part of a molecule responsible for its color, due to absorption of light in the UV-visible spectrum.
Examples include –NO₂, –N=N–, and –C=C– groups.
57. Give two examples of amino penicillins.
Answer:
Ampicillin
Amoxicillin
Both are broad-spectrum β-lactam antibiotics with amino groups.
58. Explain the function of Biparatides.
Answer:
Biparatides are monoclonal antibodies that bind to two different epitopes of the same or different antigens, improving targeting efficiency in therapies like cancer or autoimmune diseases.
59. Define partition coefficient.
Answer:
Partition coefficient (P) is the ratio of a compound’s concentration in a lipophilic phase (usually octanol) to its concentration in a hydrophilic phase (usually water).
It indicates lipophilicity and membrane permeability.
60. What is Posaconazole?
Answer:
Posaconazole is a triazole antifungal agent used to treat invasive fungal infections like aspergillosis and candidiasis.
It inhibits lanosterol 14-α-demethylase, blocking ergosterol synthesis.
Structure of Posaconazole:
B.Pharmacy 6th Semester All Subject Important Short Question Answer
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