Introduction: This quiz set focuses on free radicals and their roles in diabetes, neurodegeneration, and cancer — topics critical for M.Pharm students studying Advanced Pharmacology-II. The questions emphasize mechanistic pathways of reactive oxygen and nitrogen species (ROS/RNS), key enzymatic defenses, biomarkers, and pharmacological strategies to modulate oxidative stress. Topics include mitochondrial ROS, NADPH oxidases, AGE–RAGE signaling, Nrf2-mediated responses, ferroptosis, and clinically relevant antioxidants and inhibitors. These MCQs are designed to deepen understanding of pathophysiology and therapeutic targets, sharpen reasoning for exams, and support evidence-based drug development perspectives in oxidative-stress–related diseases.
Q1. What is the principal intracellular source of excessive reactive oxygen species (ROS) in hyperglycemia associated with diabetes?
- Mitochondrial electron transport chain (complex I/III)
- NADPH oxidase (NOX) activation
- Xanthine oxidase induction
- Uncoupled endothelial nitric oxide synthase (eNOS)
Correct Answer: Mitochondrial electron transport chain (complex I/III)
Q2. Which hyperglycemia-driven pathways collectively contribute to elevated ROS generation in diabetic complications?
- Polyol pathway flux, protein kinase C activation, and formation of advanced glycation end products (AGEs)
- Hexosamine pathway activation only
- Mitochondrial biogenesis increase exclusively
- Decreased fatty acid oxidation alone
Correct Answer: Polyol pathway flux, protein kinase C activation, and formation of advanced glycation end products (AGEs)
Q3. Which biomarker is most commonly used to quantify oxidative DNA damage in clinical and experimental studies?
- Malondialdehyde (MDA)
- 8-hydroxy-2′-deoxyguanosine (8-OHdG)
- Protein carbonyl content
- Total antioxidant capacity (TAC)
Correct Answer: 8-hydroxy-2′-deoxyguanosine (8-OHdG)
Q4. Which enzyme catalyzes the dismutation of superoxide anion (O2•−) to hydrogen peroxide (H2O2) in cells?
- Glutathione peroxidase (GPx)
- Superoxide dismutase (SOD)
- Catalase
- Peroxiredoxin
Correct Answer: Superoxide dismutase (SOD)
Q5. Which transcription factor is the master regulator of inducible antioxidant and phase II detoxifying enzyme expression?
- NF-κB (nuclear factor kappa B)
- HIF-1α (hypoxia-inducible factor 1-alpha)
- Nrf2 (nuclear factor erythroid 2–related factor 2)
- AP-1 (activator protein 1)
Correct Answer: Nrf2 (nuclear factor erythroid 2–related factor 2)
Q6. Which pharmacological agent is used to supply cysteine for glutathione synthesis and is a clinically used antioxidant?
- Ascorbic acid (vitamin C)
- Alpha-tocopherol (vitamin E)
- N-acetylcysteine (NAC)
- Edaravone
Correct Answer: N-acetylcysteine (NAC)
Q7. Peroxynitrite (ONOO−), a potent reactive nitrogen species implicated in neurodegeneration, is formed by reaction between which two radicals?
- Hydroxyl radical (•OH) and nitrogen dioxide (•NO2)
- Hydrogen peroxide (H2O2) and nitrite (NO2−)
- Superoxide (O2•−) and nitric oxide (NO•)
- Lipid peroxyl radical (LOO•) and nitroxyl (HNO)
Correct Answer: Superoxide (O2•−) and nitric oxide (NO•)
Q8. Which of the following is a widely used lipid peroxidation marker measured in plasma and tissues?
- 8-OHdG
- Malondialdehyde (MDA)
- C-reactive protein (CRP)
- Glutathione-S-transferase (GST) activity
Correct Answer: Malondialdehyde (MDA)
Q9. How does oxidative stress primarily impair pancreatic beta-cell function in diabetes?
- By direct inhibition of insulin receptor signaling in peripheral tissues
- By oxidative damage to mitochondrial DNA and ATP production impairing insulin secretion
- By inducing excessive insulin gene transcription leading to ER stress
- By increasing beta-cell proliferation and dedifferentiation
Correct Answer: By oxidative damage to mitochondrial DNA and ATP production impairing insulin secretion
Q10. In Parkinson’s disease pathogenesis, what role does dopamine autoxidation play in oxidative injury?
- Dopamine autoxidation consumes iron and reduces oxidative burden
- Dopamine autoxidation generates hydrogen peroxide and toxic quinones that damage neurons
- Dopamine autoxidation increases glutathione synthesis and neuroprotection
- Dopamine autoxidation exclusively activates synaptic vesicle recycling
Correct Answer: Dopamine autoxidation generates hydrogen peroxide and toxic quinones that damage neurons
Q11. Advanced glycation end products (AGEs) enhance oxidative stress in diabetic vascular disease mainly by which mechanism?
- Directly scavenging superoxide and reducing ROS
- Binding to RAGE and activating NADPH oxidase signaling
- Inhibiting mitochondrial respiration to lower ROS production
- Stimulating insulin secretion to decrease glucose toxicity
Correct Answer: Binding to RAGE and activating NADPH oxidase signaling
Q12. Which molecular intervention is most likely to induce ferroptosis in cancer cells as a therapeutic strategy?
- Activation of catalase
- Inhibition of glutathione peroxidase 4 (GPX4)
- Overexpression of superoxide dismutase (SOD)
- Enhancement of mitochondrial complex I activity
Correct Answer: Inhibition of glutathione peroxidase 4 (GPX4)
Q13. Which key antioxidant enzyme is a selenium-containing selenoprotein essential for detoxifying hydrogen peroxide and lipid hydroperoxides?
- Glutathione peroxidase (GPx)
- Catalase
- Peroxiredoxin 6 (PRDX6)
- Thioredoxin reductase (TrxR)
Correct Answer: Glutathione peroxidase (GPx)
Q14. How do ROS contribute to both initiation and progression of cancer?
- By solely promoting apoptosis and tumor regression
- By inducing DNA damage and mutations while activating redox-sensitive proliferative signaling
- By preventing angiogenesis and inhibiting metastasis
- By exclusively blocking cell cycle progression at G0/G1
Correct Answer: By inducing DNA damage and mutations while activating redox-sensitive proliferative signaling
Q15. Which NADPH oxidase isoform is most consistently implicated in diabetic vascular oxidative stress and endothelial dysfunction?
- NOX2 only
- NOX1 only
- NOX4 (NADPH oxidase 4)
- NOX5 exclusively
Correct Answer: NOX4 (NADPH oxidase 4)
Q16. Excessive activation of poly(ADP-ribose) polymerase (PARP) during oxidative DNA damage leads to cell death primarily through which mechanism?
- Enhanced DNA repair capacity and cell survival
- Depletion of NAD+ and ATP causing energetic collapse and necrotic cell death
- Immediate activation of caspase-dependent apoptosis only
- Direct inhibition of mitochondrial respiration complexes increasing ATP production
Correct Answer: Depletion of NAD+ and ATP causing energetic collapse and necrotic cell death
Q17. Which assay is commonly used to detect intracellular ROS generation by fluorescent measurement in cell-based studies?
- Dichlorofluorescin diacetate (DCFDA) fluorescence assay
- ELISA for tumor necrosis factor-alpha (TNF-α)
- Western blot for catalase expression
- qPCR of antioxidant genes only
Correct Answer: Dichlorofluorescin diacetate (DCFDA) fluorescence assay
Q18. What is the consequence of mitochondrial permeability transition pore (mPTP) opening in response to oxidative stress?
- Enhanced ATP synthesis and improved cell survival
- Release of cytochrome c, loss of membrane potential, increased ROS and initiation of apoptosis/necrosis
- Immediate stabilization of mitochondrial DNA and reduced ROS
- Exclusive activation of autophagy without cell death
Correct Answer: Release of cytochrome c, loss of membrane potential, increased ROS and initiation of apoptosis/necrosis
Q19. Which free radical scavenger has demonstrated clinical benefit and is used acutely in ischemic stroke as a neuroprotective agent?
- Vitamin C (oral high dose)
- Edaravone (radical scavenger)
- Glutathione infusion
- Buthionine sulfoximine (BSO)
Correct Answer: Edaravone (radical scavenger)
Q20. Constitutive activation of Nrf2 in certain tumors contributes to chemoresistance primarily by which mechanism?
- Downregulation of glutathione and phase II enzymes
- Upregulation of antioxidant defenses and drug-detoxifying enzymes, lowering intracellular ROS and drug efficacy
- Increase in pro-oxidant enzyme expression only
- Induction of permanent cell cycle arrest that sensitizes cells to chemotherapy
Correct Answer: Upregulation of antioxidant defenses and drug-detoxifying enzymes, lowering intracellular ROS and drug efficacy
