Acetate pathway MCQs With Answer

Acetate pathway MCQs With Answer

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Acetate pathway MCQs With Answer

The acetate pathway encompasses biochemical routes that produce or consume acetate, including the bacterial phosphotransacetylase–acetate kinase (Pta–Ack) system, acetyl-CoA synthetase reactions, and the Wood–Ljungdahl (reductive acetyl‑CoA) pathway in acetogens. For B. Pharm students, understanding enzymes (acetate kinase, phosphotransacetylase, acetyl‑CoA synthetase), cofactors (CoA, ATP, TPP), bioenergetics, metabolic regulation, and links to fatty acid synthesis and drug-relevant acetylation is essential. These MCQs focus on mechanisms, regulation, cellular roles, and clinical or pharmaceutical relevance of acetate metabolism to build applied competence. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which enzyme catalyzes the conversion of acetyl phosphate to acetate, generating ATP in many bacteria?

  • Phosphotransacetylase
  • Acetyl‑CoA synthetase
  • Acetate kinase
  • Pyruvate dehydrogenase

Correct Answer: Acetate kinase

Q2. The combined Pta–Ack pathway in bacteria refers to which pair of enzymes?

  • Pyruvate oxidase and lactate dehydrogenase
  • Phosphotransacetylase and acetate kinase
  • Acetyl‑CoA synthetase and citrate synthase
  • Acetyltransferase and carboxylase

Correct Answer: Phosphotransacetylase and acetate kinase

Q3. Acetyl‑CoA synthetase (AMP‑forming) activates acetate to acetyl‑CoA using which stoichiometry?

  • ATP → ADP + Pi
  • ATP → AMP + PPi
  • GTP → GDP + Pi
  • ATP + CoA → acetyl‑phosphate

Correct Answer: ATP → AMP + PPi

Q4. The Wood–Ljungdahl pathway is primarily used by which group of organisms?

  • Facultative aerobes that oxidize glucose
  • Acetogenic bacteria that fix CO2 to acetate
  • Animals during fatty acid synthesis
  • Yeasts during ethanol fermentation

Correct Answer: Acetogenic bacteria that fix CO2 to acetate

Q5. Which high‑energy intermediate links acetyl‑CoA to ATP production in the acetate pathway?

  • Acetyl phosphate
  • Acetyl‑carnitine
  • Malonyl‑CoA
  • Succinyl‑CoA

Correct Answer: Acetyl phosphate

Q6. In E. coli under anaerobic fermentation, pyruvate is converted into acetate via which immediate acetyl‑CoA forming step?

  • Pyruvate → lactate via lactate dehydrogenase
  • Pyruvate → acetyl‑CoA via pyruvate dehydrogenase/pyruvate formate‑lyase
  • Pyruvate → oxaloacetate via pyruvate carboxylase
  • Pyruvate → ethanol via alcohol dehydrogenase

Correct Answer: Pyruvate → acetyl‑CoA via pyruvate dehydrogenase/pyruvate formate‑lyase

Q7. Which cofactor is essential for pyruvate dehydrogenase complex to form acetyl‑CoA from pyruvate?

  • Biotin
  • Thiamine pyrophosphate (TPP)
  • FAD only
  • Nicotinamide riboside

Correct Answer: Thiamine pyrophosphate (TPP)

Q8. Activation of acetate in eukaryotic cells for lipid synthesis is mainly catalyzed by which enzyme?

  • Acetate kinase
  • Acetyl‑CoA synthetase (ACS)
  • Acetyl‑phosphate hydrolase
  • Acyl‑CoA oxidase

Correct Answer: Acetyl‑CoA synthetase (ACS)

Q9. Which vitamin is the biochemical precursor for coenzyme A (CoA), required in acetate and acetyl‑CoA metabolism?

  • Riboflavin (B2)
  • Pantothenic acid (B5)
  • Niacin (B3)
  • Folate (B9)

Correct Answer: Pantothenic acid (B5)

Q10. Formation of acetate from acetyl‑CoA via the Pta–Ack pathway yields what direct energetic benefit to the cell?

  • Generation of NADH
  • Substrate‑level phosphorylation producing ATP
  • Production of FADH2 for oxidative phosphorylation
  • Net consumption of ATP

Correct Answer: Substrate‑level phosphorylation producing ATP

Q11. Which metabolite serves as the methyl donor during the methyl branch of the Wood–Ljungdahl pathway?

  • S‑adenosylmethionine (SAM)
  • Methyl‑tetrahydrofolate (methyl‑THF)
  • Methyl‑B12 independent carrier
  • Acetyl‑CoA

Correct Answer: Methyl‑tetrahydrofolate (methyl‑THF)

Q12. Acetyl phosphate can act as a phosphoryl donor in bacteria for which regulatory system?

  • Glyoxylate shunt induction
  • Two‑component response regulator phosphorylation
  • Electron transport chain complex I activation
  • Ribosomal protein synthesis initiation

Correct Answer: Two‑component response regulator phosphorylation

Q13. Which cellular transporter primarily mediates uptake and release of short‑chain fatty acids like acetate in mammalian cells?

  • ABC transporter A1
  • Monocarboxylate transporter (MCT) family
  • Sodium–glucose cotransporter (SGLT)
  • Glucose transporter (GLUT) family

Correct Answer: Monocarboxylate transporter (MCT) family

Q14. In the context of histone modification, acetate is transferred from acetyl‑CoA to lysine residues by which enzyme class?

  • Histone deacetylases (HDACs)
  • Histone acetyltransferases (HATs)
  • Kinases
  • Methyltransferases

Correct Answer: Histone acetyltransferases (HATs)

Q15. Which statement best describes the net ATP yield difference between converting glucose to acetate versus complete oxidation to CO2 via TCA/oxidative phosphorylation?

  • Conversion to acetate yields more ATP per glucose than complete oxidation
  • Both yield equal ATP per glucose
  • Complete oxidation to CO2 yields significantly more ATP than fermentation to acetate
  • ATP yield depends only on oxygen concentration, not pathway

Correct Answer: Complete oxidation to CO2 yields significantly more ATP than fermentation to acetate

Q16. Which enzyme produces acetyl phosphate from acetyl‑CoA in the bacterial acetate pathway?

  • Acetate kinase
  • Phosphotransacetylase
  • Acetyl‑CoA carboxylase
  • Acetyl transferase I

Correct Answer: Phosphotransacetylase

Q17. During ethanol metabolism in the liver, ethanol is ultimately converted to acetate via acetaldehyde; which enzyme converts acetate to acetyl‑CoA for entry into the TCA cycle?

  • Acetaldehyde dehydrogenase
  • Acetyl‑CoA synthetase (ACS)
  • Alcohol dehydrogenase
  • Acetate kinase

Correct Answer: Acetyl‑CoA synthetase (ACS)

Q18. Which metabolite derived from acetyl‑CoA is the immediate two‑carbon donor used in fatty acid chain elongation?

  • Malonyl‑CoA
  • Acetyl‑phosphate
  • Acetyl‑carnitine
  • Succinyl‑CoA

Correct Answer: Malonyl‑CoA

Q19. Which enzyme activity is absent in many eukaryotes, making the bacterial Pta–Ack route uncommon in higher organisms?

  • Phosphotransacetylase and acetate kinase activities
  • ATP synthase activity
  • Pyruvate carboxylase activity
  • Acetyl‑CoA carboxylase activity

Correct Answer: Phosphotransacetylase and acetate kinase activities

Q20. The primary electron donor for CO2 reduction in many acetogens operating the Wood–Ljungdahl pathway is typically:

  • Oxygen
  • Molecular hydrogen (H2)
  • NADPH only
  • Glucose

Correct Answer: Molecular hydrogen (H2)

Q21. Accumulation of acetyl phosphate in bacteria can lead to which downstream effect?

  • Inactivation of two‑component signaling by dephosphorylation
  • Non‑enzymatic phosphorylation of response regulators altering gene expression
  • Direct use in fatty acid elongation
  • Export out of cell as an energy waste product

Correct Answer: Non‑enzymatic phosphorylation of response regulators altering gene expression

Q22. Which enzyme converts acetyl‑CoA into malonyl‑CoA, committing carbon to fatty acid biosynthesis?

  • Acetyl‑CoA carboxylase (ACC)
  • Acetate kinase
  • Citrate synthase
  • Malate dehydrogenase

Correct Answer: Acetyl‑CoA carboxylase (ACC)

Q23. In bacterial genetics, knockout of the ackA gene encoding acetate kinase would most likely cause accumulation of which metabolite?

  • Acetate
  • Acetyl phosphate
  • Acetyl‑CoA synthetase
  • Malonyl‑CoA

Correct Answer: Acetyl phosphate

Q24. Which cellular compartment in mammalian liver primarily converts acetate to acetyl‑CoA for ketone body synthesis?

  • Peroxisome
  • Mitochondrion
  • Endoplasmic reticulum
  • Golgi apparatus

Correct Answer: Mitochondrion

Q25. Which of the following best describes the role of acetyl‑CoA in central metabolism?

  • Terminal electron acceptor in respiration
  • Central two‑carbon donor linking carbohydrate, lipid and protein metabolism
  • Primary storage form of energy in cells
  • Unique metabolite only produced in bacteria

Correct Answer: Central two‑carbon donor linking carbohydrate, lipid and protein metabolism

Q26. Which prosthetic group is essential in enzymes that carry acyl groups as thioesters, such as acetyl‑CoA dependent enzymes?

  • Pyridoxal phosphate (PLP)
  • Coenzyme A (CoA) derived from pantothenate
  • Heme group
  • Biotin

Correct Answer: Coenzyme A (CoA) derived from pantothenate

Q27. In microbial bioenergetics, why is conversion of acetyl‑CoA to acetate sometimes favored under anaerobic conditions?

  • It conserves carbon for biomass only
  • It generates substrate‑level ATP and regenerates electron carriers
  • It consumes oxygen to increase energy yield
  • It prevents formation of acetyl phosphate

Correct Answer: It generates substrate‑level ATP and regenerates electron carriers

Q28. Which of the following enzymes is directly responsible for releasing free acetate (not acetyl‑CoA) in bacteria?

  • Citrate lyase
  • Acetate kinase acting on acetyl phosphate
  • Acetyl‑CoA carboxylase
  • Isocitrate dehydrogenase

Correct Answer: Acetate kinase acting on acetyl phosphate

Q29. Which receptor in mammalian cells senses short‑chain fatty acids like acetate and can mediate signaling relevant to metabolism and immunity?

  • GPR43 (FFAR2)
  • Insulin receptor
  • Toll‑like receptor 4 (TLR4)
  • Glucagon receptor

Correct Answer: GPR43 (FFAR2)

Q30. In metabolic engineering to boost acetate production from glucose in bacteria, increasing flux through which enzyme would be most directly effective?

  • Acetyl‑CoA carboxylase
  • Phosphotransacetylase
  • Isocitrate lyase
  • Malate synthase

Correct Answer: Phosphotransacetylase

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