Formation of ketone bodies MCQs With Answer

Formation of ketone bodies MCQs With Answer is a focused study resource designed for B. Pharm students to master ketogenesis, regulation, clinical implications, and biochemical pathways. This introduction covers ketone body synthesis in liver mitochondria, key enzymes like mitochondrial HMG‑CoA synthase and HMG‑CoA lyase, major products (acetoacetate, β‑hydroxybutyrate, acetone), hormonal control by insulin and glucagon, and the metabolic context of fasting, diabetes, and alcohol. Emphasis on mechanisms, enzyme regulation, NADH/NAD+ effects, and diagnostic tests will help pharmacy students understand therapeutic and clinical relevance. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Where are ketone bodies primarily synthesized?

• Liver mitochondria
• Adipose tissue cytosol
• Pancreatic beta cells
• Skeletal muscle sarcoplasm

Correct Answer: Liver mitochondria

Q2. Which enzyme is considered the rate-limiting enzyme of ketogenesis?

• Mitochondrial HMG‑CoA synthase
• HMG‑CoA reductase
• Acetoacetyl‑CoA thiolase
• Succinyl‑CoA:3‑ketoacid CoA transferase (thiophorase)

Correct Answer: Mitochondrial HMG‑CoA synthase

Q3. HMG‑CoA lyase catalyzes the formation of which primary ketone body?

• Acetoacetate
• Glucose
• Malonyl‑CoA
• Citrate

Correct Answer: Acetoacetate

Q4. Which of the following are the major ketone bodies produced in the liver?

• Acetoacetate, β‑hydroxybutyrate, and acetone
• Acetyl‑CoA, malonyl‑CoA, and citrate
• Pyruvate, lactate, and alanine
• Cholesterol, bile acids, and triglycerides

Correct Answer: Acetoacetate, β‑hydroxybutyrate, and acetone

Q5. Which enzyme reduces acetoacetate to β‑hydroxybutyrate?

• β‑Hydroxybutyrate dehydrogenase
• Acetyl‑CoA carboxylase
• HMG‑CoA reductase
• Pyruvate dehydrogenase

Correct Answer: β‑Hydroxybutyrate dehydrogenase

Q6. An increased NADH/NAD+ ratio in the liver will shift ketone production toward which compound?

• β‑Hydroxybutyrate
• Acetoacetate
• Acetone
• Oxaloacetate

Correct Answer: β‑Hydroxybutyrate

Q7. Which tissue can adapt to use ketone bodies as a major fuel during prolonged fasting?

• Brain
• Red blood cells
• Adipose tissue (for release)
• Hepatocytes (for oxidation)

Correct Answer: Brain

Q8. Which enzyme required for ketone utilization is absent in liver, preventing hepatic oxidation of ketone bodies?

• Succinyl‑CoA:3‑ketoacid CoA transferase (thiophorase)
• β‑Hydroxybutyrate dehydrogenase
• Acetoacetyl‑CoA thiolase
• HMG‑CoA lyase

Correct Answer: Succinyl‑CoA:3‑ketoacid CoA transferase (thiophorase)

Q9. The nitroprusside reagent (acetest) detects which ketone bodies in urine?

• Acetoacetate and acetone
• β‑Hydroxybutyrate only
• All three: acetoacetate, β‑hydroxybutyrate, and acetone
• None of the ketone bodies

Correct Answer: Acetoacetate and acetone

Q10. Which hormonal change most strongly promotes hepatic ketogenesis?

• Low insulin and high glucagon
• High insulin and low glucagon
• Elevated thyroid hormone only
• High growth hormone alone

Correct Answer: Low insulin and high glucagon

Q11. The carbon source for ketone body synthesis is primarily:

• Acetyl‑CoA derived from fatty acid β‑oxidation and ketogenic amino acids
• Glucose from glycolysis
• Oxaloacetate from the TCA cycle
• Fructose from the liver

Correct Answer: Acetyl‑CoA derived from fatty acid β‑oxidation and ketogenic amino acids

Q12. Uncontrolled type 1 diabetes leads to increased ketogenesis because of:

• Absolute insulin deficiency and increased lipolysis
• Excessive insulin action
• Increased glycogen synthesis
• Decreased glucagon secretion

Correct Answer: Absolute insulin deficiency and increased lipolysis

Q13. Acetone is formed from acetoacetate by which process?

• Spontaneous decarboxylation (non‑enzymatic)
• HMG‑CoA synthase action
• Succinyl‑CoA transferase reaction
• β‑Oxidation in mitochondria

Correct Answer: Spontaneous decarboxylation (non‑enzymatic)

Q14. Clinical ketosis refers to which of the following?

• Elevated levels of ketone bodies in blood and urine
• Low blood glucose with normal ketone levels
• Increased glycogen storage
• Excess insulin causing hypoglycemia

Correct Answer: Elevated levels of ketone bodies in blood and urine

Q15. Which hormone directly inhibits ketogenesis?

• Insulin
• Glucagon
• Epinephrine
• Cortisol

Correct Answer: Insulin

Q16. Which amino acids are exclusively ketogenic?

• Leucine and lysine
• Alanine and glycine
• Glutamine and asparagine
• Serine and cysteine

Correct Answer: Leucine and lysine

Q17. The enzyme that condenses two acetyl‑CoA molecules to form acetoacetyl‑CoA is:

• Acetoacetyl‑CoA thiolase (thiolase)
• HMG‑CoA lyase
• Pyruvate carboxylase
• Malate dehydrogenase

Correct Answer: Acetoacetyl‑CoA thiolase (thiolase)

Q18. Oxaloacetate depletion favors ketogenesis because:

• Acetyl‑CoA cannot enter the TCA cycle and is diverted to ketone synthesis
• It directly activates HMG‑CoA lyase
• It increases glycolysis
• It enhances glycogen synthesis

Correct Answer: Acetyl‑CoA cannot enter the TCA cycle and is diverted to ketone synthesis

Q19. The primary metabolic source of acetyl‑CoA for ketogenesis is:

• Fatty acid β‑oxidation
• Glycogenolysis
• Pentose phosphate pathway
• Gluconeogenesis from lactate

Correct Answer: Fatty acid β‑oxidation

Q20. Alcoholic ketoacidosis often shows a high β‑hydroxybutyrate to acetoacetate ratio because alcohol metabolism:

• Increases the hepatic NADH/NAD+ ratio
• Decreases NADH production
• Inhibits alcohol dehydrogenase
• Increases insulin secretion

Correct Answer: Increases the hepatic NADH/NAD+ ratio

Q21. For accurate clinical measurement of ketone burden in diabetic ketoacidosis, which analyte is preferred?

• Blood β‑hydroxybutyrate concentration
• Urine nitroprusside test only
• Breath acetone level only
• Blood acetoacetate concentration only

Correct Answer: Blood β‑hydroxybutyrate concentration

Q22. Which organ is unable to utilize ketone bodies for energy due to lack of thiophorase?

• Liver
• Heart
• Skeletal muscle
• Kidney cortex

Correct Answer: Liver

Q23. After the onset of prolonged fasting, approximately how many days until the brain significantly uses ketone bodies?

• About 3 days
• Immediately within hours
• After 2 weeks only
• Never; brain cannot use ketones

Correct Answer: About 3 days

Q24. How are ketone bodies transported in the blood?

• They are water‑soluble and circulate dissolved in plasma
• They are bound tightly to albumin
• They are transported within lipoprotein particles
• They require specific carrier proteins like hemoglobin

Correct Answer: They are water‑soluble and circulate dissolved in plasma

Q25. Ketone bodies cross the blood–brain barrier primarily via:

• Monocarboxylate transporters (MCTs)
• Glucose transporters (GLUTs)
• Fatty acid transport proteins
• Endocytosis only

Correct Answer: Monocarboxylate transporters (MCTs)

Q26. There are isoforms of HMG‑CoA synthase. Which isoform is involved in ketogenesis?

• Mitochondrial HMG‑CoA synthase (HMGCS2)
• Cytosolic HMG‑CoA synthase for cholesterol synthesis
• Peroxisomal HMG‑CoA synthase
• Endoplasmic reticulum HMG‑CoA synthase

Correct Answer: Mitochondrial HMG‑CoA synthase (HMGCS2)

Q27. The cofactor used by β‑hydroxybutyrate dehydrogenase for the reversible reaction is:

• NAD+/NADH
• FAD/FADH2
• Biotin
• PLP (pyridoxal phosphate)

Correct Answer: NAD+/NADH

Q28. Acetone is clinically significant because it is:

• Volatile and gives a fruity odor on the breath
• Used as the main energy substrate for the brain
• Detected by nitroprusside test only
• A high‑energy metabolite converted to ATP

Correct Answer: Volatile and gives a fruity odor on the breath

Q29. During diabetic ketoacidosis (DKA), which ketone is usually predominant?

• β‑Hydroxybutyrate
• Acetoacetate
• Acetone
• Acetyl‑CoA

Correct Answer: β‑Hydroxybutyrate

Q30. Which of the following laboratory tests can underestimate total ketone burden in DKA?

• Nitroprusside urine test
• Blood β‑hydroxybutyrate assay
• Arterial blood gas for pH
• Serum electrolyte panel

Correct Answer: Nitroprusside urine test

Q31. Which amino acid is both glucogenic and ketogenic?

• Isoleucine
• Leucine (only ketogenic)
• Lysine (only ketogenic)
• Alanine (only glucogenic)

Correct Answer: Isoleucine

Q32. In peripheral tissues, which enzyme converts acetoacetate to acetoacetyl‑CoA for oxidation?

• Succinyl‑CoA:3‑ketoacid CoA transferase (thiophorase)
• HMG‑CoA lyase
• HMG‑CoA synthase
• Acetoacetate decarboxylase

Correct Answer: Succinyl‑CoA:3‑ketoacid CoA transferase (thiophorase)

Q33. Ketogenesis is increased in which nutritional state?

• Prolonged fasting
• Fed state after carbohydrate meal
• High‑insulin infusion
• Postprandial lipogenesis

Correct Answer: Prolonged fasting

Q34. Which statement about hepatic ketone metabolism is true?

• Liver produces ketone bodies but does not oxidize them due to lack of thiophorase
• Liver both produces and extensively oxidizes ketone bodies
• Liver cannot produce ketone bodies at all
• Liver converts ketones back to glucose directly

Correct Answer: Liver produces ketone bodies but does not oxidize them due to lack of thiophorase

Q35. A primary carnitine deficiency would have what effect on ketone body formation?

• Decrease ketone body production due to impaired fatty acid entry into mitochondria
• Increase ketone production due to excess fatty acid oxidation
• No effect on ketogenesis
• Convert ketogenesis to cholesterol synthesis

Correct Answer: Decrease ketone body production due to impaired fatty acid entry into mitochondria

Q36. Inhibition of carnitine palmitoyltransferase I (CPT I) would cause:

• Reduced hepatic ketogenesis
• Increased ketone body production
• No change in fatty acid oxidation
• Enhanced transport of fatty acids into mitochondria

Correct Answer: Reduced hepatic ketogenesis

Q37. HMG‑CoA lyase is localized in which cellular compartment?

• Mitochondrial matrix
• Endoplasmic reticulum lumen
• Cytosol
• Peroxisome

Correct Answer: Mitochondrial matrix

Q38. Which metabolic change favors conversion of acetoacetate to β‑hydroxybutyrate?

• High mitochondrial NADH
• High mitochondrial NAD+
• Low acetyl‑CoA levels
• High oxaloacetate concentration

Correct Answer: High mitochondrial NADH

Q39. Why can the nitroprusside test lead to false reassurance in severe DKA?

• It does not detect β‑hydroxybutyrate, which may predominate
• It is overly sensitive to β‑hydroxybutyrate
• It measures blood glucose instead of ketones
• It detects only cholesterol derivatives

Correct Answer: It does not detect β‑hydroxybutyrate, which may predominate

Q40. Accumulation of ketone bodies can lead to metabolic acidosis because:

• They are acidic and release protons in blood
• They raise blood bicarbonate levels
• They directly increase insulin secretion
• They convert to ammonia

Correct Answer: They are acidic and release protons in blood

Q41. Which of the following is NOT a ketone body?

• Acetyl‑CoA
• Acetoacetate
• β‑Hydroxybutyrate
• Acetone

Correct Answer: Acetyl‑CoA

Q42. Insulin reduces ketogenesis primarily by:

• Decreasing lipolysis and fatty acid supply to the liver
• Activating HMG‑CoA synthase
• Increasing hepatic fatty acid oxidation
• Stimulating glucagon release

Correct Answer: Decreasing lipolysis and fatty acid supply to the liver

Q43. A therapeutic ketogenic diet increases ketone production and is used clinically for which condition?

• Refractory epilepsy
• Acute bacterial infections
• Hyperinsulinemic hypoglycemia
• Acute pancreatitis

Correct Answer: Refractory epilepsy

Q44. Which cofactor provides the CoA necessary for conversion of acetoacetate into acetoacetyl‑CoA in peripheral tissues?

• Succinyl‑CoA donates CoA via thiophorase
• Free coenzyme Q10 directly supplies CoA
• Biotin supplies the CoA group
• PLP transfers CoA

Correct Answer: Succinyl‑CoA donates CoA via thiophorase

Q45. What initiates increased hepatic ketone synthesis during fasting?

• Enhanced mobilization and β‑oxidation of fatty acids
• Immediate rise in blood glucose
• Decreased glucagon secretion
• Increased dietary carbohydrate intake

Correct Answer: Enhanced mobilization and β‑oxidation of fatty acids

Q46. How does mitochondrial HMG‑CoA synthase differ functionally from the cytosolic HMG‑CoA pathway?

• Mitochondrial HMG‑CoA synthase participates in ketone synthesis, cytosolic pathway supplies cholesterol precursors
• Both isoforms produce ketone bodies equally
• Cytosolic HMG‑CoA synthase makes acetoacetate for ketogenesis
• Only cytosolic HMG‑CoA synthase is regulated by fasting

Correct Answer: Mitochondrial HMG‑CoA synthase participates in ketone synthesis, cytosolic pathway supplies cholesterol precursors

Q47. Which statement about acetone is correct?

• It is a volatile byproduct that is mostly exhaled or excreted and not used for major ATP production
• It is the primary ATP‑yielding ketone in muscle
• It is directly converted to glucose in the liver
• It is detected preferentially by the nitroprusside test

Correct Answer: It is a volatile byproduct that is mostly exhaled or excreted and not used for major ATP production

Q48. Why does the liver produce ketone bodies but not use them for its own energy?

• The liver lacks the thiophorase enzyme required for ketone utilization
• The liver has a special transporter that excludes ketones
• The liver converts all ketones immediately to cholesterol
• The liver uses only glucose as an energy source

Correct Answer: The liver lacks the thiophorase enzyme required for ketone utilization

Q49. Oxidation of odd‑chain fatty acids leads predominantly to products that:

• Enter gluconeogenesis (propionyl‑CoA → succinyl‑CoA)
• Directly form acetoacetate only
• Produce large amounts of acetone
• Are converted into cholesterol exclusively

Correct Answer: Enter gluconeogenesis (propionyl‑CoA → succinyl‑CoA)

Q50. For emergency monitoring of ketoacidosis in a hospital, which measurement is most reliable to track treatment response?

• Serial blood β‑hydroxybutyrate levels
• Single urine nitroprusside test at admission only
• Fasting blood glucose alone
• Breath acetone qualitative smell only

Correct Answer: Serial blood β‑hydroxybutyrate levels

G S Sachin

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.

Mail- Sachin@pharmacyfreak.com