Free radical theory of ageing MCQs With Answer

Free radical theory of ageing MCQs With Answer — This focused review introduces B. Pharm students to the free radical theory of ageing, explaining how reactive oxygen species (ROS) and oxidative stress drive cellular senescence via mitochondrial dysfunction, lipid peroxidation, protein oxidation and DNA damage. Key biochemical pathways, such as Fenton and Haber–Weiss reactions, enzymatic antioxidants (SOD, catalase, glutathione peroxidase), and biomarkers like MDA and 8‑OHdG are covered. Therapeutic approaches, including antioxidant drugs, pro-oxidant hormesis, chelators and lifestyle interventions, are discussed for pharmacological relevance. Clear, clinically oriented MCQs with answers will reinforce mechanism-based learning. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which species is primarily described in the free radical theory of ageing as causing oxidative cellular damage?

• Reactive oxygen species (ROS)
• Glutathione
• ATP
• Insulin

Correct Answer: Reactive oxygen species (ROS)

Q2. The Fenton reaction involves which metal catalyzing the conversion of hydrogen peroxide to hydroxyl radical?

• Magnesium
• Iron
• Calcium
• Zinc

Correct Answer: Iron

Q3. Which enzyme catalyzes dismutation of superoxide anion into hydrogen peroxide and oxygen?

• Catalase
• Glutathione reductase
• Superoxide dismutase (SOD)
• Peroxidase

Correct Answer: Superoxide dismutase (SOD)

Q4. Malondialdehyde (MDA) is commonly measured as a biomarker of:

• Protein glycation
• Lipid peroxidation
• DNA methylation
• Carbohydrate metabolism

Correct Answer: Lipid peroxidation

Q5. 8‑OHdG (8‑hydroxy‑2′‑deoxyguanosine) is used as a marker for:

• Protein oxidation
• RNA synthesis
• Oxidative DNA damage
• Lipid peroxidation

Correct Answer: Oxidative DNA damage

Q6. Which of the following is a non-enzymatic antioxidant commonly studied in ageing research?

• Glutathione peroxidase
• Vitamin E (alpha-tocopherol)
• Superoxide dismutase
• Catalase

Correct Answer: Vitamin E (alpha-tocopherol)

Q7. Mitochondrial theory of ageing is closely linked to free radical theory because mitochondria are a major source of:

• Reactive oxygen species (ROS)
• Glucose
• Ribosomes
• Lysosomes

Correct Answer: Reactive oxygen species (ROS)

Q8. Which reaction describes the interaction between superoxide and nitric oxide producing peroxynitrite?

• Haber–Weiss reaction
• Fenton reaction
• Superoxide–nitric oxide reaction
• Oxidative phosphorylation

Correct Answer: Superoxide–nitric oxide reaction

Q9. Glutathione peroxidase requires which cofactor for activity in mammalian cells?

• Selenium
• Iron
• Copper
• Zinc

Correct Answer: Selenium

Q10. The Haber–Weiss reaction overall converts superoxide and hydrogen peroxide into which highly reactive species?

• Hydroxyl radical
• Singlet oxygen
• Hypochlorous acid
• Peroxide anion

Correct Answer: Hydroxyl radical

Q11. TBARS assay commonly measures which oxidative stress product?

• 8‑OHdG
• Malondialdehyde (MDA)
• Protein carbonyls
• Glutathione

Correct Answer: Malondialdehyde (MDA)

Q12. Which cellular macromolecule is LEAST susceptible to direct free radical attack compared to others?

• Polyunsaturated lipids
• DNA
• Proteins
• Glycogen

Correct Answer: Glycogen

Q13. Which pharmacological agent is used as a glutathione precursor and antioxidant in clinical practice?

• N‑acetylcysteine (NAC)
• Acetylsalicylic acid
• Propranolol
• Omeprazole

Correct Answer: N‑acetylcysteine (NAC)

Q14. ‘Hormesis’ in the context of oxidative stress refers to:

• High-dose antioxidants always preventing ageing
• Beneficial adaptive responses to low levels of stressors
• Irreversible cellular damage from ROS
• Complete absence of ROS in cells

Correct Answer: Beneficial adaptive responses to low levels of stressors

Q15. NADPH oxidase (NOX) contributes to ROS production primarily in:

• Mitochondrial matrix
• Plasma membrane and phagocytes
• Ribosomes
• Golgi apparatus

Correct Answer: Plasma membrane and phagocytes

Q16. Which of the following best describes chain propagation in lipid peroxidation?

• Initiation of radical formation by UV light only
• Lipid radical reacting with oxygen to form peroxyl radical that attacks other lipids
• Antioxidants producing radicals
• Proteins breaking down lipids enzymatically

Correct Answer: Lipid radical reacting with oxygen to form peroxyl radical that attacks other lipids

Q17. Which assay detects single- and double-strand DNA breaks due to oxidative stress at the single-cell level?

• ELISA for MDA
• Comet assay (single-cell gel electrophoresis)
• Western blot for SOD
• TBARS assay

Correct Answer: Comet assay (single-cell gel electrophoresis)

Q18. Chronic oxidative stress can accelerate cellular ageing by promoting which process associated with cell-cycle exit?

• Autophagy activation only
• Cellular senescence
• Uncontrolled proliferation
• Immediate apoptosis in all cells

Correct Answer: Cellular senescence

Q19. Which antioxidant enzyme converts hydrogen peroxide into water and oxygen?

• Superoxide dismutase (SOD)
• Catalase
• Glutathione reductase
• NADPH oxidase

Correct Answer: Catalase

Q20. Peroxynitrite (ONOO−) formation results from reaction between superoxide and which molecule, producing nitration of proteins?

• Nitric oxide (NO)
• Hydrogen peroxide (H2O2)
• Glutathione (GSH)
• Oxygen (O2)

Correct Answer: Nitric oxide (NO)

Q21. Which dietary antioxidant is lipid-soluble and protects membranes from peroxidation?

• Vitamin C (ascorbic acid)
• Vitamin E (alpha-tocopherol)
• Glutathione
• Uric acid

Correct Answer: Vitamin E (alpha-tocopherol)

Q22. Mitochondrial DNA (mtDNA) is more susceptible to oxidative damage than nuclear DNA mainly because:

• mtDNA is protected by histones
• mtDNA is close to ROS production sites and has limited repair mechanisms
• mtDNA is double-stranded while nuclear DNA is single-stranded
• mtDNA has superior antioxidant enzymes

Correct Answer: mtDNA is close to ROS production sites and has limited repair mechanisms

Q23. Which of the following enzymes regenerates reduced glutathione (GSH) from oxidized glutathione (GSSG)?

• Glutathione peroxidase
• Glutathione reductase
• Glutathione S‑transferase
• Catalase

Correct Answer: Glutathione reductase

Q24. In pharmacology, pro-oxidant anticancer strategies exploit ROS by:

• Reducing ROS to protect cancer cells
• Inducing excessive ROS to trigger cancer cell death
• Neutralizing all ROS systemically
• Stimulating mitochondrial biogenesis only

Correct Answer: Inducing excessive ROS to trigger cancer cell death

Q25. Which of these is a reactive nitrogen species implicated in nitrosative stress and ageing?

• Hydroxyl radical (•OH)
• Peroxynitrite (ONOO−)
• Singlet oxygen (1O2)
• Superoxide dismutase (SOD)

Correct Answer: Peroxynitrite (ONOO−)

Q26. Which pharmacological class includes metal chelators used to limit Fenton chemistry in oxidative stress?

• ACE inhibitors
• Iron chelators (e.g., deferoxamine)
• Beta blockers
• Statins

Correct Answer: Iron chelators (e.g., deferoxamine)

Q27. Telomere shortening linked to oxidative stress accelerates cellular ageing because:

• ROS lengthen telomeres by adding bases
• Oxidative damage impairs telomere replication and promotes shortening
• Telomeres are resistant to oxidative stress
• Telomerase is activated by ROS to elongate telomeres

Correct Answer: Oxidative damage impairs telomere replication and promotes shortening

Q28. Which clinical test would a pharmacologist choose to assess systemic antioxidant capacity in plasma?

• Ferric reducing antioxidant power (FRAP) assay
• PCR for mtDNA deletions
• Glucose tolerance test
• Complete blood count

Correct Answer: Ferric reducing antioxidant power (FRAP) assay

Q29. Which of the following statements best reflects limitations of exogenous antioxidant supplementation for ageing?

• All antioxidants uniformly extend lifespan in humans
• High-dose antioxidants can disrupt redox signaling and may be ineffective or harmful
• Antioxidants always accumulate in mitochondria without modification
• Antioxidants replace the need for endogenous enzymes entirely

Correct Answer: High-dose antioxidants can disrupt redox signaling and may be ineffective or harmful

Q30. Caloric restriction may slow ageing partly by reducing ROS through which mechanism?

• Increasing mitochondrial proton leak and improving efficiency, lowering ROS production
• Completely stopping mitochondrial respiration
• Increasing dietary iron absorption to neutralize ROS
• Inhibiting all antioxidant enzymes

Correct Answer: Increasing mitochondrial proton leak and improving efficiency, lowering ROS production

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