Understanding the Shikimic acid pathway is essential for B. Pharm students because the shikimate pathway (shikimic acid pathway) produces aromatic amino acids (phenylalanine, tyrosine, tryptophan) and many secondary metabolites, and is a key target in drug and herbicide development. This concise review highlights critical enzymes (DAHP synthase, shikimate dehydrogenase, shikimate kinase, EPSP synthase, chorismate synthase), intermediates (DAHP, shikimate-3-phosphate, EPSP, chorismate), regulation, and pharmaceutical implications including enzyme inhibitors like glyphosate. These Shikimic acid pathway MCQs With Answer emphasize mechanism, regulation, enzyme targets, and clinical relevance to strengthen exam preparation and problem-solving skills for B. Pharm students. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which two central metabolites condense to form the first committed intermediate in the shikimate pathway?
- Glucose and fructose-6-phosphate
- Phosphoenolpyruvate (PEP) and erythrose-4-phosphate (E4P)
- Acetyl-CoA and malonyl-CoA
- Pyruvate and glyceraldehyde-3-phosphate
Correct Answer: Phosphoenolpyruvate (PEP) and erythrose-4-phosphate (E4P)
Q2. Which enzyme catalyzes formation of 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP), the first committed step of the shikimate pathway?
- Shikimate kinase
- DAHP synthase
- EPSP synthase
- Chorismate synthase
Correct Answer: DAHP synthase
Q3. What is the direct product formed by DAHP synthase action?
- Shikimate
- Chorismate
- 3-Deoxy-D-arabino-heptulosonate-7-phosphate (DAHP)
- 5-Enolpyruvylshikimate-3-phosphate (EPSP)
Correct Answer: 3-Deoxy-D-arabino-heptulosonate-7-phosphate (DAHP)
Q4. Which enzyme phosphorylates shikimate to form shikimate-3-phosphate?
- Shikimate dehydrogenase
- Shikimate kinase
- EPSP synthase
- DAHP synthase
Correct Answer: Shikimate kinase
Q5. Which enzyme in the shikimate pathway is the primary target of the herbicide glyphosate?
- Shikimate dehydrogenase
- DAHP synthase
- EPSP synthase (5-enolpyruvylshikimate-3-phosphate synthase)
- Chorismate mutase
Correct Answer: EPSP synthase (5-enolpyruvylshikimate-3-phosphate synthase)
Q6. Which statement best explains why the shikimate pathway is an attractive drug target?
- It is present and essential in humans, allowing direct metabolic inhibition
- It is absent in humans but present in microorganisms and plants, enabling selective toxicity
- It directly generates nucleotides required for DNA synthesis in humans
- It is the main pathway for lipid biosynthesis in mammals
Correct Answer: It is absent in humans but present in microorganisms and plants, enabling selective toxicity
Q7. What is the key branchpoint metabolite at the end of the shikimate pathway that gives rise to aromatic amino acids?
- Shikimate-3-phosphate
- 5-Enolpyruvylshikimate-3-phosphate (EPSP)
- Chorismate
- DAHP
Correct Answer: Chorismate
Q8. Which enzyme converts chorismate into anthranilate, the first committed step toward tryptophan biosynthesis?
- Chorismate mutase
- Anthranilate synthase
- Prephenate dehydratase
- Tryptophan synthase
Correct Answer: Anthranilate synthase
Q9. EPSP synthase catalyzes the formation of EPSP from shikimate-3-phosphate and which other substrate?
- ATP
- Phosphoenolpyruvate (PEP)
- NADPH
- Pyruvate
Correct Answer: Phosphoenolpyruvate (PEP)
Q10. Which cofactor is required by shikimate dehydrogenase to reduce 3-dehydroshikimate to shikimate?
- ATP
- NADH
- NADPH
- FAD
Correct Answer: NADPH
Q11. Chorismate mutase catalyzes the conversion of chorismate into which intermediate for phenylalanine and tyrosine biosynthesis?
- Shikimate
- Prephenate
- Anthranilate
- EPSP
Correct Answer: Prephenate
Q12. In many bacteria, which gene designation commonly corresponds to EPSP synthase?
- aroB
- aroA
- trpE
- aroC
Correct Answer: aroA
Q13. Which enzyme catalyzes dehydration of 3-dehydroquinate to form 3-dehydroshikimate?
- 3-Dehydroquinate synthase
- 3-Dehydroquinate dehydratase
- Shikimate dehydrogenase
- Shikimate kinase
Correct Answer: 3-Dehydroquinate dehydratase
Q14. Which aromatic amino acid biosynthesis branch begins with anthranilate formation from chorismate?
- Phenylalanine
- Tyrosine
- Tryptophan
- Histidine
Correct Answer: Tryptophan
Q15. Which enzyme catalyzes the conversion of EPSP to chorismate?
- EPSP synthase
- Chorismate synthase
- Shikimate kinase
- DAHP synthase
Correct Answer: Chorismate synthase
Q16. Which of the following is the active herbicidal inhibitor of EPSP synthase widely known in agriculture?
- Paraquat
- Glyphosate
- Atrazine
- 2,4-Dichlorophenoxyacetic acid
Correct Answer: Glyphosate
Q17. DAHP synthase activity is typically regulated by feedback inhibition from which molecules?
- ATP and ADP
- Aromatic amino acids (phenylalanine, tyrosine, tryptophan)
- Fatty acids
- Glucose-6-phosphate
Correct Answer: Aromatic amino acids (phenylalanine, tyrosine, tryptophan)
Q18. Shikimate kinase requires which of the following to catalyze phosphorylation of shikimate?
- Only ATP
- ATP and Mg2+
- NADH and Mg2+
- FAD and ATP
Correct Answer: ATP and Mg2+
Q19. In plant cells, in which subcellular compartment does the shikimate pathway primarily occur?
- Cytosol
- Mitochondria
- Plastids (chloroplasts)
- Peroxisomes
Correct Answer: Plastids (chloroplasts)
Q20. Why must humans obtain aromatic amino acids from the diet?
- Humans rapidly degrade aromatic amino acids so they must be eaten continuously
- Humans lack the shikimate pathway and cannot synthesize these amino acids
- Dietary uptake is required for protein folding in humans
- Humans can synthesize them but prefer dietary sources
Correct Answer: Humans lack the shikimate pathway and cannot synthesize these amino acids
Q21. Chorismate is a precursor for which class of biomolecules?
- Branched-chain amino acids
- Aromatic amino acids and related aromatic compounds
- Pyrimidine nucleotides
- Triglycerides
Correct Answer: Aromatic amino acids and related aromatic compounds
Q22. Which enzyme class best describes EPSP synthase based on its catalytic action?
- Oxidoreductase
- Ligase
- Transferase
- Isomerase
Correct Answer: Transferase
Q23. Which compound acts as a transition-state mimic and inhibits EPSP synthase?
- Chloramphenicol
- Glyphosate
- Penicillin
- Streptomycin
Correct Answer: Glyphosate
Q24. Which intermediate is reduced by shikimate dehydrogenase to give shikimate?
- DAHP
- 3-Dehydroshikimate
- EPSP
- Chorismate
Correct Answer: 3-Dehydroshikimate
Q25. What is the primary function of chorismate mutase in aromatic amino acid biosynthesis?
- Converting chorismate to prephenate for phenylalanine and tyrosine synthesis
- Phosphorylating shikimate to shikimate-3-phosphate
- Reducing 3-dehydroshikimate to shikimate
- Synthesizing anthranilate for tryptophan
Correct Answer: Converting chorismate to prephenate for phenylalanine and tyrosine synthesis
Q26. Genes designated as aro in bacteria typically encode enzymes of which metabolic pathway?
- Glycolysis
- Shikimate (aromatic amino acid) pathway
- TCA cycle
- Pentose phosphate pathway
Correct Answer: Shikimate (aromatic amino acid) pathway
Q27. Anthranilate synthase uses which amino acid as the nitrogen donor in conversion of chorismate to anthranilate?
- Asparagine
- Glutamine
- Lysine
- Arginine
Correct Answer: Glutamine
Q28. Chorismate is a metabolic precursor for p-aminobenzoate (PABA), which is a key precursor for which vitamin?
- Vitamin B12
- Folate (Vitamin B9)
- Vitamin C
- Biotin (Vitamin B7)
Correct Answer: Folate (Vitamin B9)
Q29. Chorismate synthase belongs to which enzyme class based on the reaction it catalyzes?
- Isomerase
- Lyase
- Hydrolase
- Oxidoreductase
Correct Answer: Lyase
Q30. Which statement best summarizes why inhibitors of the shikimate pathway can be selectively toxic to microbes and plants but safe for humans?
- Humans possess redundant shikimate enzymes making inhibitors ineffective
- The pathway is absent in humans but essential in microbes and plants, allowing selective inhibition
- Inhibitors cannot cross human cell membranes
- Human enzymes rapidly degrade such inhibitors
Correct Answer: The pathway is absent in humans but essential in microbes and plants, allowing selective inhibition
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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