Classification of secondary metabolites MCQs With Answer is a concise, exam-oriented guide for B.Pharm students focused on the chemical classes, biosynthetic pathways and pharmacological relevance of secondary metabolites. This introduction highlights keywords like secondary metabolites, classification, alkaloids, terpenoids, phenolics, shikimate pathway, mevalonate pathway, biosynthesis, pharmacognosy and bioactive natural products. Emphasis is placed on structural families, diagnostic chemical tests, representative drug examples and ecological functions such as defense and signaling. The material is tailored to deepen conceptual understanding and support applied learning in medicinal chemistry and pharmacognosy. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What best defines secondary metabolites?
- Primary biomolecules indispensable for growth and reproduction
- Non-essential compounds involved in defense and ecological interactions
- Only proteins and carbohydrates used for energy
- Metabolites produced exclusively during seed germination
Correct Answer: Non-essential compounds involved in defense and ecological interactions
Q2. Which of the following lists major classes of secondary metabolites?
- Carbohydrates, proteins, nucleic acids
- Alkaloids, terpenoids, phenolics, glycosides
- Vitamins, minerals, lipids
- Enzymes, cofactors, prosthetic groups
Correct Answer: Alkaloids, terpenoids, phenolics, glycosides
Q3. Which precursor is central to terpenoid biosynthesis?
- Shikimic acid
- Isopentenyl diphosphate (IPP)
- Amino acids like tryptophan
- Glucose-6-phosphate
Correct Answer: Isopentenyl diphosphate (IPP)
Q4. Which pathways produce isoprenoid precursors for terpenoids?
- Glycolysis and pentose phosphate pathways
- Mevalonate (MVA) and MEP/DOXP pathways
- Urea cycle and β-oxidation
- Shikimate and Calvin cycles
Correct Answer: Mevalonate (MVA) and MEP/DOXP pathways
Q5. Alkaloids are generally biosynthesized from which type of precursor?
- Isoprene units
- Amino acids
- Fatty acids
- Nucleotide bases
Correct Answer: Amino acids
Q6. Which alkaloid is a classic opioid analgesic derived from Papaver somniferum?
- Quinine
- Morphine
- Atropine
- Caffeine
Correct Answer: Morphine
Q7. Which cardiac glycoside is obtained from Digitalis species and used clinically?
- Digoxin
- Reserpine
- Codeine
- Artemisinin
Correct Answer: Digoxin
Q8. Phenolic compounds commonly originate from which biosynthetic pathway?
- Mevalonate pathway
- Shikimate pathway
- Beta-oxidation of fatty acids
- Glycolysis exclusively
Correct Answer: Shikimate pathway
Q9. Flavonoids belong to which chemical class?
- Terpenoids
- Alkaloids
- Polyphenolics
- Polyketides
Correct Answer: Polyphenolics
Q10. Monoterpenes consist of how many carbon atoms?
- 5 carbons
- 10 carbons
- 15 carbons
- 20 carbons
Correct Answer: 10 carbons
Q11. Which reagent is commonly used to detect alkaloids in plant extracts?
- Fehling’s reagent
- Dragendorff’s reagent
- Salkowski reagent
- Benedict’s reagent
Correct Answer: Dragendorff’s reagent
Q12. Which chemical test is used for anthraquinone glycosides?
- Borntrager’s test
- Kjeldahl test
- Molisch test
- Biuret test
Correct Answer: Borntrager’s test
Q13. Which property is characteristic of saponins?
- Form stable foams and show hemolytic activity
- Strongly basic and precipitate with tannic acid
- Volatile aromatic molecules only
- Unable to form emulsions
Correct Answer: Form stable foams and show hemolytic activity
Q14. Polyketides are mainly synthesized from which building blocks?
- Isopentenyl diphosphate units
- Acetyl-CoA and malonyl-CoA extender units
- Amino acid decarboxylation products
- Monosaccharide units
Correct Answer: Acetyl-CoA and malonyl-CoA extender units
Q15. Which terpenoid is an important anticancer drug isolated from Taxus species?
- Resveratrol
- Paclitaxel (Taxol)
- Curcumin
- Quinine
Correct Answer: Paclitaxel (Taxol)
Q16. Quinine, used against malaria, is classified as which type of secondary metabolite?
- A terpenoid
- An alkaloid
- A flavonoid
- A glycoside of a steroid
Correct Answer: An alkaloid
Q17. Secondary metabolites serve ecological roles; which is NOT a common role?
- Defense against herbivores and pathogens
- Attraction of pollinators via pigmentation
- Primary ATP production for cellular metabolism
- Allelopathic interactions with neighboring plants
Correct Answer: Primary ATP production for cellular metabolism
Q18. Hydrolysis of a glycoside yields which products?
- Two carbohydrates
- An aglycone and a sugar
- Two amino acids
- Only CO2 and water
Correct Answer: An aglycone and a sugar
Q19. Tannins are broadly classified into which two groups?
- Saponins and alkaloids
- Hydrolyzable and condensed tannins
- Monoterpenes and diterpenes
- Glycosides and aglycones
Correct Answer: Hydrolyzable and condensed tannins
Q20. Lignans are formed by the dimerization of which units?
- Isoprene units
- Phenylpropanoid units
- Monosaccharides
- Fatty acid methyl esters
Correct Answer: Phenylpropanoid units
Q21. Indole alkaloids are biosynthesized from which amino acid precursor?
- Tyrosine
- Tryptophan
- Phenylalanine
- Lysine
Correct Answer: Tryptophan
Q22. The aglycone of cardiac glycosides typically contains which core structure?
- Flavone nucleus
- Steroid nucleus (cardenolide/bufadienolide)
- Indole ring system
- Monoterpene skeleton
Correct Answer: Steroid nucleus (cardenolide/bufadienolide)
Q23. Which phenolic compound is a well-known antioxidant found in many fruits?
- Quercetin
- Atropine
- Nicotine
- Digitoxin
Correct Answer: Quercetin
Q24. Which pathway is responsible for biosynthesis of aromatic amino acids (phenylalanine, tyrosine, tryptophan)?
- MVA pathway
- Shikimate pathway
- Urea cycle
- Glyoxylate cycle
Correct Answer: Shikimate pathway
Q25. How do secondary metabolites differ from primary metabolites?
- They are essential for basic cell survival
- They are produced only in microorganisms
- They are not essential for basic growth but confer adaptive advantages
- They are identical across all species
Correct Answer: They are not essential for basic growth but confer adaptive advantages
Q26. Which statement about alkaloids is true?
- They are neutral lipids without nitrogen
- They are basic nitrogen-containing compounds often pharmacologically active
- They are polymers of isoprene units
- They are exclusively carbohydrates
Correct Answer: They are basic nitrogen-containing compounds often pharmacologically active
Q27. Terpenoids are biosynthetically assembled from which repeating unit?
- Glucose monomers
- Isoprene (C5) units
- Amino acid dimers
- Acetate only
Correct Answer: Isoprene (C5) units
Q28. Polyketide natural products are typically synthesized by which enzyme system?
- Polyketide synthases (PKS)
- Ribonuclease complexes
- Peroxisomal oxidases only
- ATP synthase
Correct Answer: Polyketide synthases (PKS)
Q29. Atropine is a tropane alkaloid classically isolated from which plant?
- Cinchona officinalis
- Atropa belladonna (deadly nightshade)
- Digitalis purpurea
- Taxus baccata
Correct Answer: Atropa belladonna (deadly nightshade)
Q30. Which analytical technique is most commonly used for initial screening and qualitative separation of plant secondary metabolites?
- Nuclear magnetic resonance (NMR) spectroscopy
- TLC (Thin Layer Chromatography)
- X-ray crystallography
- Mass spectrometry only
Correct Answer: TLC (Thin Layer Chromatography)
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