Energy-rich compounds – classification MCQs With Answer

Energy-rich compounds – classification MCQs With Answer

Understanding energy-rich compounds is essential for B. Pharm students studying biochemical energetics, drug metabolism and pharmacology. This concise introduction covers classification of high-energy bonds, examples such as ATP, phosphagens, acyl-phosphates, thioesters, and principles like phosphate transfer potential, resonance stabilization and hydrolysis energetics. Key terms include high-energy phosphate bonds, substrate-level phosphorylation, oxidative phosphorylation, acetyl-CoA and clinical relevance in drug action and cellular bioenergetics. These focused MCQs will deepen your grasp of how different classes compare in energy yield, enzymatic formation and metabolic roles — vital for biopharmaceutics and medicinal chemistry applications. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which of the following is considered the primary cellular energy currency?

• Adenosine triphosphate (ATP)
• Creatine
• Acetyl-CoA
• Glucose-6-phosphate

Correct Answer: Adenosine triphosphate (ATP)

Q2. Which bond in ATP is typically described as a high-energy bond responsible for most energy release on hydrolysis?

• Glycosidic bond
• Phosphoanhydride bond
• Peptide bond
• Phosphoester bond

Correct Answer: Phosphoanhydride bond

Q3. Phosphocreatine is categorized as which type of energy-rich compound?

• Thioester
• Enol phosphate
• Phosphagen
• Acyl phosphate

Correct Answer: Phosphagen

Q4. Acetyl-CoA is an example of which class of high-energy compound?

• Enol phosphate
• Thioester
• Polyphosphate
• Phosphagen

Correct Answer: Thioester

Q5. Which compound has a higher phosphate transfer potential than ATP?

• Glucose
• Phosphoenolpyruvate (PEP)
• ADP
• Glycerol

Correct Answer: Phosphoenolpyruvate (PEP)

Q6. Hydrolysis of which bond yields inorganic phosphate (Pi) and ADP?

• ATP γ-phosphate hydrolysis
• ATP α-phosphate hydrolysis
• Peptide bond hydrolysis
• Phosphocreatine hydrolysis to creatine

Correct Answer: ATP γ-phosphate hydrolysis

Q7. Which factor contributes most to the high free energy of hydrolysis of ATP?

• Increased steric hindrance
• Resonance stabilization of products and charge repulsion relief
• Higher molecular weight of ADP
• Hydrophobicity of phosphate

Correct Answer: Resonance stabilization of products and charge repulsion relief

Q8. Which enzyme synthesizes ATP during oxidative phosphorylation?

• Pyruvate kinase
• ATP synthase (F0F1-ATPase)
• Hexokinase
• Lactate dehydrogenase

Correct Answer: ATP synthase (F0F1-ATPase)

Q9. In substrate-level phosphorylation, the direct donor of phosphate to ADP is typically which type of compound?

• Low-energy alcohol phosphate
• Energy-rich intermediate such as 1,3-bisphosphoglycerate or PEP
• Fatty acid
• Free inorganic phosphate alone

Correct Answer: Energy-rich intermediate such as 1,3-bisphosphoglycerate or PEP

Q10. Which nucleotide triphosphate serves as an energy source specifically in protein synthesis for activation of amino acids?

• CTP
• GTP
• UTP
• TTP

Correct Answer: GTP

Q11. Which statement best describes a thioester bond like that in acetyl-CoA?

• It is less reactive than an oxygen ester and stores little energy
• It is formed by a sulfur atom linking acyl group to coenzyme A and is energy-rich
• It contains a phosphoanhydride linkage
• It is found only in nucleotides

Correct Answer: It is formed by a sulfur atom linking acyl group to coenzyme A and is energy-rich

Q12. Which compound is an enol phosphate with a very high phosphoryl transfer potential used in glycolysis?

• 3-phosphoglycerate
• Phosphoenolpyruvate (PEP)
• Fructose-6-phosphate
• Ribose-5-phosphate

Correct Answer: Phosphoenolpyruvate (PEP)

Q13. Which property explains why inorganic pyrophosphate (PPi) hydrolysis drives many biosynthetic reactions?

• PPi hydrolysis is endergonic
• PPi hydrolysis has large negative ΔG and removal of PPi shifts equilibrium
• PPi hydrolysis generates free radicals
• PPi is hydrophobic and insoluble

Correct Answer: PPi hydrolysis has large negative ΔG and removal of PPi shifts equilibrium

Q14. Which of the following is NOT typically classified as an energy-rich compound?

• Adenosine diphosphate (ADP)
• Adenosine monophosphate (AMP)
• Acetyl-CoA
• Phosphocreatine

Correct Answer: Adenosine monophosphate (AMP)

Q15. The standard free energy change (ΔG°’) for ATP hydrolysis to ADP + Pi is approximately:

• +30 kJ/mol
• −30 kJ/mol
• 0 kJ/mol
• −100 kJ/mol

Correct Answer: −30 kJ/mol

Q16. Which molecule directly activates carboxyl groups in fatty acid synthesis via a high-energy bond?

• ATP alone
• Acyl carrier protein without activation
• Acyl-adenylate intermediate (acyl-AMP)
• Glucose-6-phosphate

Correct Answer: Acyl-adenylate intermediate (acyl-AMP)

Q17. Which high-energy compound stores energy in some bacteria as a polyphosphate chain?

• Polyphosphate (polyP)
• Triacylglycerol
• Phosphatidylcholine
• Cholesterol ester

Correct Answer: Polyphosphate (polyP)

Q18. Creatine kinase catalyzes the reversible transfer of phosphate between ATP and which compound?

• AMP
• Creatine
• Acetyl-CoA
• Glucose

Correct Answer: Creatine

Q19. Which of the following best describes why ATP hydrolysis is coupled to unfavorable reactions?

• ATP hydrolysis consumes water making reactions irreversible
• ATP hydrolysis provides a large negative ΔG that can make overall pathway favorable
• ATP binds irreversibly to enzymes
• ATP raises the pH to favor reactions

Correct Answer: ATP hydrolysis provides a large negative ΔG that can make overall pathway favorable

Q20. Which of the following is an acyl phosphate example involved in bacterial metabolism?

• Acetyl phosphate
• Glucose-1-phosphate
• Phosphocreatine
• Citrate

Correct Answer: Acetyl phosphate

Q21. Which class of compounds generally has higher phosphoryl transfer potential: acyl-phosphates or ordinary phosphoesters?

• Ordinary phosphoesters
• Acyl-phosphates
• Both are equal
• Neither transfers phosphate

Correct Answer: Acyl-phosphates

Q22. Which process regenerates ATP from ADP using a proton gradient across a membrane?

• Substrate-level phosphorylation
• Oxidative phosphorylation
• Fermentation
• Glycolysis alone

Correct Answer: Oxidative phosphorylation

Q23. Which factor does NOT directly increase the standard free energy of hydrolysis of an energy-rich compound?

• Resonance stabilization of products
• Relief of electrostatic repulsion
• Increased hydration of products
• Higher molecular mass of the reactant

Correct Answer: Higher molecular mass of the reactant

Q24. During glycolysis, which compound donates phosphate to ADP to form ATP via pyruvate kinase?

• 1,3-bisphosphoglycerate
• 2-phosphoglycerate
• Phosphoenolpyruvate (PEP)
• Fructose-6-phosphate

Correct Answer: Phosphoenolpyruvate (PEP)

Q25. Which molecule functions as a high-energy electron carrier closely linked to energy-rich compound metabolism?

• NADH
• Sucrose
• Urea
• Cholesterol

Correct Answer: NADH

Q26. Which high-energy functional group is characteristic of nucleotide triphosphates?

• Phosphoester only
• Phosphoanhydride linkages between phosphate groups
• Thioester linkage
• Ether linkage

Correct Answer: Phosphoanhydride linkages between phosphate groups

Q27. Which enzyme class transfers phosphate groups from ATP to substrates and is crucial for signaling?

• Hydrolases
• Kinases
• Ligases
• Isomerases

Correct Answer: Kinases

Q28. Which statement correctly relates ATP hydrolysis and activation energy of coupled reactions?

• ATP hydrolysis increases activation energy of reactions
• ATP hydrolysis supplies free energy to lower the overall ΔG but may not alter activation energy directly
• ATP hydrolysis always prevents enzyme catalysis
• ATP hydrolysis converts endergonic steps into exothermic reactions by heat alone

Correct Answer: ATP hydrolysis supplies free energy to lower the overall ΔG but may not alter activation energy directly

Q29. Which compound is produced from AMP by adding two phosphate groups enzymatically?

• ADP then ATP
• cAMP
• Urea
• Glucose

Correct Answer: ADP then ATP

Q30. Which of the following best defines “phosphate transfer potential”?

• Ability of a molecule to hold phosphorus atoms
• Tendency of a phosphorylated compound to transfer its phosphate to water
• Relative tendency to donate phosphate to ADP or another acceptor
• Speed of phosphate group migration within a molecule

Correct Answer: Relative tendency to donate phosphate to ADP or another acceptor

Q31. Which of the following reactions is an example of substrate-level phosphorylation?

• ATP synthesis by ATP synthase during oxidative phosphorylation
• Conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate forming ATP
• Formation of acetyl-CoA from pyruvate by pyruvate dehydrogenase complex
• Photophosphorylation in chloroplasts

Correct Answer: Conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate forming ATP

Q32. Which compound’s hydrolysis yields AMP and pyrophosphate, often used in biosynthetic activation?

• ATP forming ADP + Pi
• ATP forming AMP + PPi
• ADP forming AMP + Pi
• GTP forming GDP + Pi

Correct Answer: ATP forming AMP + PPi

Q33. In terms of biochemical classification, where would 1,3-bisphosphoglycerate be placed?

• Thioester
• Acyl-phosphate (acyl-phosphate intermediate)
• Phosphagen
• Polyphosphate

Correct Answer: Acyl-phosphate (acyl-phosphate intermediate)

Q34. Which high-energy compound is commonly analyzed to assess cellular energy charge?

• Amino acids pool
• ATP, ADP and AMP levels
• Cholesterol to phospholipid ratio
• Glycogen concentration

Correct Answer: ATP, ADP and AMP levels

Q35. Which of the following increases cellular AMP concentration and activates AMP-activated protein kinase (AMPK)?

• High ATP/ADP ratio
• Cellular energy deficit increasing AMP
• Excess glucose uptake
• Overproduction of NADPH

Correct Answer: Cellular energy deficit increasing AMP

Q36. Which compound contains a phosphoanhydride bond but is more stable than ATP under physiological conditions?

• ADP
• ATP
• Guanosine monophosphate (GMP)
• Phosphocreatine

Correct Answer: ADP

Q37. Which high-energy compound participates directly in gluconeogenesis by consuming ATP equivalents?

• Acetyl-CoA
• Phosphoenolpyruvate carboxykinase uses GTP
• Urea
• Cholesterol

Correct Answer: Phosphoenolpyruvate carboxykinase uses GTP

Q38. Which functional explanation accounts for thioesters having high free energy of hydrolysis?

• Strong resonance stabilization of the thioester reactant compared to products
• Poor resonance stabilization of thioester compared to carboxylate products leading to energy release
• Thioesters are more hydrophobic which generates heat on hydrolysis
• Thioesters form more hydrogen bonds on hydrolysis

Correct Answer: Poor resonance stabilization of thioester compared to carboxylate products leading to energy release

Q39. Which compound directly functions as a phosphate donor in glycogen synthesis?

• UDP-glucose (uridine diphosphate glucose)
• ATP only
• Free glucose
• cAMP

Correct Answer: UDP-glucose (uridine diphosphate glucose)

Q40. Which of the following energy-rich bonds is commonly hydrolyzed by kinases?

• Phosphoanhydride bond between β and γ phosphates of ATP
• Peptide bond in proteins
• Glycosidic bond in sugars
• Thioester in acetyl-CoA

Correct Answer: Phosphoanhydride bond between β and γ phosphates of ATP

Q41. Which high-energy intermediate is involved in activation of fatty acids prior to β-oxidation?

• Fatty acyl-CoA (acyl-CoA)
• Free fatty acid without activation
• Triacylglycerol
• Fatty alcohol

Correct Answer: Fatty acyl-CoA (acyl-CoA)

Q42. Which of the following best explains why acetyl-CoA is central to metabolism?

• It is stored as a long-term energy reserve like fat
• It links carbohydrate, fat and protein catabolism via its thioester high-energy bond
• It functions as an electron carrier like NADH
• It serves primarily as an osmolyte

Correct Answer: It links carbohydrate, fat and protein catabolism via its thioester high-energy bond

Q43. Which technique is commonly used to measure cellular ATP levels in the lab?

• Western blotting
• Luciferase-based bioluminescence assay
• Thin-layer chromatography for lipids
• Gram staining

Correct Answer: Luciferase-based bioluminescence assay

Q44. Which of the following is a consequence of hydrolyzing ATP to AMP and PPi in biosynthetic reactions?

• Reaction becomes less favorable due to PPi accumulation
• Hydrolysis of PPi to 2Pi makes the overall process irreversible and thermodynamically favorable
• No net energy change occurs
• AMP is immediately converted to cAMP increasing signaling

Correct Answer: Hydrolysis of PPi to 2Pi makes the overall process irreversible and thermodynamically favorable

Q45. Which compound is an example of a mixed anhydride high-energy compound found in metabolism?

• ATP only
• 1,3-bisphosphoglycerate
• Cholesterol ester
• Glucose

Correct Answer: 1,3-bisphosphoglycerate

Q46. Which statement best differentiates phosphoester and phosphoanhydride bonds in terms of energy?

• Phosphoesters generally have higher hydrolysis free energy than phosphoanhydrides
• Phosphoanhydrides generally store more free energy than phosphoesters
• They have identical free energy of hydrolysis
• Phosphoesters are completely inert biologically

Correct Answer: Phosphoanhydrides generally store more free energy than phosphoesters

Q47. Which high-energy compound provides the acetyl group for the tricarboxylic acid (TCA) cycle entry?

• Acetyl-CoA
• Pyruvate alone without activation
• ATP
• Glucose-6-phosphate

Correct Answer: Acetyl-CoA

Q48. Which enzyme catalyzes formation of ATP from ADP in glycolysis via substrate-level phosphorylation?

• Hexokinase
• Phosphoglycerate kinase and pyruvate kinase
• Aconitase
• Isocitrate dehydrogenase

Correct Answer: Phosphoglycerate kinase and pyruvate kinase

Q49. Which of the following is true about guanosine triphosphate (GTP) compared to ATP?

• GTP cannot be hydrolyzed by cells
• GTP functions as an energy source in specific reactions such as protein synthesis and gluconeogenesis
• GTP is only involved in lipid metabolism
• GTP has no phosphoryl transfer potential

Correct Answer: GTP functions as an energy source in specific reactions such as protein synthesis and gluconeogenesis

Q50. Which of the following accurately classifies energy-rich biological compounds into main groups?

• Only nucleotides and sugars
• Phosphagens, acyl-phosphates, enol-phosphates, thioesters and polyphosphates
• Lipids and water only
• Only amino acids and vitamins

Correct Answer: Phosphagens, acyl-phosphates, enol-phosphates, thioesters and polyphosphates

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.

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