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
