Antioxidants and Minerals MCQs

Biochemistry · 17 free questions with answers & explanations.

1. A 25-year-old woman with Wilson's disease has liver cirrhosis and Kayser-Fleischer rings. The primary metabolic defect is impaired:
2. Superoxide dismutase (SOD) is a primary antioxidant enzyme that converts superoxide radicals to hydrogen peroxide. The subsequent detoxification of hydrogen peroxide in hepatocytes is primarily accomplished by:
3. A 3-year-old child from a low-income household has microcytic hypochromic anemia, poor wound healing, and perifollicular hemorrhages. Serum ferritin is normal. Which micronutrient deficiency best explains the full clinical picture?
4. Ceruloplasmin is a copper-containing plasma protein with ferroxidase activity. A patient with Wilson's disease (ATP7B mutation) has low serum ceruloplasmin and corneal Kayser-Fleischer rings from copper deposition. The ferroxidase activity of ceruloplasmin is clinically important because it:
5. Menkes disease (X-linked) causes severe neurodegeneration, kinky hair, seizures, and connective tissue defects in infant males due to copper deficiency despite adequate dietary intake. Which protein is defective, and how does its dysfunction cause the multi-system phenotype?
6. Selenium is an essential micronutrient incorporated as selenocysteine (Sec, the 21st amino acid) via a unique co-translational mechanism. Which feature of selenocysteine incorporation is biochemically unique?
7. Glutathione peroxidase (GPx) detoxifies H2O2 and lipid peroxides using reduced glutathione (GSH) as electron donor, generating oxidized glutathione (GSSG). Glutathione reductase restores GSH using NADPH. In G6PD deficiency, NADPH production is impaired, impairing GPx regeneration. A patient with G6PD deficiency takes primaquine (an oxidant drug) and develops hemolytic anemia. The RBC hemolysis is initiated by which molecular event?
8. Selenium is an essential trace element incorporated into selenoproteins via the amino acid selenocysteine (the 21st amino acid), encoded by UGA codon (normally a stop codon) with a special SECIS element in the 3'-UTR. Glutathione peroxidase (GPx1, GPx4) and thioredoxin reductase are selenoproteins. In severe selenium deficiency (Keshan disease — endemic in parts of China), myocardial involvement is characteristic. Selenium supplementation is also important in preventing which specific oxidative complication in premature neonates?
9. Superoxide dismutase (SOD) catalyzes the conversion of superoxide radical to hydrogen peroxide. In the cytosol, the primary SOD isoform is SOD1 (Cu/Zn-SOD). Mutations in the SOD1 gene are associated with which neurodegenerative disease?
10. Wilson's disease (hepatolenticular degeneration) is caused by mutations in ATP7B, a copper-transporting P-type ATPase. The biochemical consequence that produces the pathognomonic Kayser-Fleischer rings in the cornea is:
11. Superoxide dismutase (SOD) catalyzes the dismutation of superoxide radical (O2•-) to hydrogen peroxide (H2O2). There are three human SOD isoforms with different metal cofactors. Which isoform is located in the mitochondrial matrix and is the primary defense against mitochondrial superoxide generated by electron leakage?
12. Selenium is an essential trace element incorporated into selenocysteine in selenoproteins. Glutathione peroxidase (GPx) is the most important selenoprotein for cellular antioxidant defense. How does GPx work in concert with glutathione reductase to maintain the cellular redox state?
13. Superoxide dismutase (SOD) catalyses the dismutation of superoxide radical to hydrogen peroxide and oxygen. Three isoforms exist in human cells. Which metalloenzyme is the mitochondrial isoform (MnSOD/SOD2), and why is its upregulation important in cancer biology?
14. Wilson's disease results from mutations in ATP7B, a copper-transporting P-type ATPase located in hepatocyte trans-Golgi. Which two functions of ATP7B are impaired in Wilson's disease, and what accounts for the elevated free serum copper despite low ceruloplasmin?
15. Menkes disease (kinky hair disease) is caused by mutations in ATP7A, a copper-exporting ATPase in intestinal enterocytes. Which copper-dependent enzymes are deficient, producing the characteristic clinical features?
16. Selenium is an essential trace element incorporated as selenocysteine (the 21st amino acid) via a unique UGA codon read-through mechanism. The primary role of selenoproteins in antioxidant defence is:
17. A patient with Wilson's disease (hepatolenticular degeneration) has decreased serum ceruloplasmin and elevated free serum copper. Ceruloplasmin's primary biochemical function, beyond copper transport, involves which antioxidant enzyme activity?