Questions and Answers
What is the primary function of Glutathione Peroxidase in relation to hydrogen peroxide?
Which amino acid is specifically involved in the structure of reduced glutathione?
Which of the following describes the relationship between NADPH and glutathione reductase?
What is the consequence of the oxidation of the sulfhydryl group in glutathione?
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What type of electrons are involved in the biradical state of molecular oxygen?
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Which of the following reactive species is NOT formed from the partial reduction of molecular oxygen?
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What role does selenium play in the function of Glutathione Peroxidase?
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How does glutathione contribute to cellular defense against oxidative stress?
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What happens to glutathione after it detoxifies hydrogen peroxide?
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Which of the following describes a purpose of modifying a drug or xenobiotic?
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What role do hydroxyl groups play in the detoxification process?
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Which of the following is NOT a feature of the oxygen-dependent bacterial killing mechanisms?
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Which white blood cells are primarily involved in the phagocytic process?
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What is the main product generated by the myeloperoxidase system during the bacterial killing process?
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How do oxygen-independent systems contribute to bacterial killing?
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Which compound is generated from superoxide through enzymatic conversion in the bacterial killing mechanisms?
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What is the function of reactive oxygen species produced during phagocytosis?
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Which xenobiotic modification leads to increased solubility for excretion?
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What triggers the respiratory burst in neutrophils during phagocytosis?
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What is the primary function of NADPH in red blood cells?
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What consequence results from a glucose 6-phosphate dehydrogenase defect?
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Which of the following enzymes is NOT directly involved in antioxidant defense against reactive oxygen species (ROS)?
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Where in the body is the highest activity of antioxidant enzymes typically found?
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What role does glutathione play in redox biology?
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The accumulation of oxidized glutathione (G-S-S-G) indicates what in cellular physiology?
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Which of the following statements about cytochrome P450 enzymes is false?
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What effect does the nonreduction of oxidized glutathione have on red blood cells?
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Superoxide dismutase and catalase work together in which of the following ways?
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Which biological compartment is least likely to contain high levels of antioxidant enzymes?
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How does decreased G6PD activity affect red blood cells in terms of oxidative stress?
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What is the relationship between G6PD enzyme activity and the severity of the disease in patients?
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Which statement accurately reflects the role of G6PD in red blood cells?
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What is a consequence of mutant enzymes with altered kinetic properties due to G6PD mutations?
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How does a mutation leading to increased resistance to Falciparum Malaria impact G6PD status?
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What is the effect of decreased NADPH formation due to reduced G6PD activity?
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What is the primary function of cGMP in vascular smooth muscle relaxation?
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Which oxidant drug is NOT listed as a precipitating factor for hemolytic anemia in G6PD deficiency?
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Which substance is primarily synthesized by eNOS in endothelial cells?
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What is the expected time frame for hemolytic effects after the consumption of fava beans in G6PD deficient patients?
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Which of the following is NOT a result of the activation of protein kinase G by cGMP?
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Which class of drugs is associated with a hemolytic reaction in patients with G6PD deficiency?
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What is the main mechanism of action for sildenafil citrate in the body?
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What is primarily responsible for the decrease in blood pressure after the action of vasodilator nitrates?
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Which of the following conditions is aggravated by G6PD deficiency?
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What is the consequence of protein kinase G activation in smooth muscle cells?
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Study Notes
Glutathione Peroxidase
- Selenium-dependent enzyme crucial for reducing hydrogen peroxide (H2O2).
- H2O2 is a reactive oxygen species formed from the incomplete reduction of molecular oxygen.
- Transitions between reduced glutathione (a tripeptide) and oxidized glutathione utilizing glutathione reductase and NADPH.
Production of Glutathione
- The reduced form of glutathione (G-SH) can be oxidized to its disulfide form (G-S-S-G).
- The hexose monophosphate (HMP) pathway provides necessary NADPH for regeneration of reduced glutathione.
- Glucose 6-phosphate dehydrogenase deficiency linked to low NADPH leads to oxidized glutathione accumulation, causing H2O2 buildup and red blood cell instability.
Antioxidant Enzymes
- Superoxide dismutase and catalase also play significant roles in antioxidant defense.
- NADPH supplies reducing equivalents necessary for cytochrome P450 monooxygenase activity in liver metabolism.
- Antioxidant enzymes are predominantly active in the liver, adrenal glands, and kidneys.
Detoxification Mechanisms
- Glutathione acts as a nonenzymatic antioxidant detoxifying xenobiotics like drugs and pollutants.
- Modifications can activate/inactivate drugs and enhance water solubility for excretion.
- Conjugation sites introduced through hydroxyl groups facilitate increased solubility, aiding in elimination.
Phagocytosis and Reactive Oxygen Species (ROS)
- White blood cells (neutrophils, macrophages, monocytes) utilize phagocytosis to ingest pathogens and debris.
- Reactive oxygen species are generated during the respiratory burst, crucial for microbial killing.
- Mechanisms include activation of NADPH oxidase leading to superoxide production followed by H2O2 and myeloperoxidase activity generating hypochlorous acid (HOCl).
G6PD Deficiency Implications
- Most individuals with G6PD deficiency remain asymptomatic, clinical symptoms arise under stress factors like oxygen exposure or specific drugs.
- Drugs like sulfonamides, chloroquine, and fava beans can precipitate hemolytic anemia due to reduced antioxidant capacity.
- Mutations affecting G6PD can result in varied enzyme activity, stability, and altered affinity for substrates.
Importance of G6PD in Red Blood Cells
- G6PD is essential for maintaining NADPH levels, which protects red blood cells from oxidative stress.
- Deficiency leads to inadequate reduced glutathione, making RBCs prone to oxidative damage and hemolysis.
- Severity of hemolytic episodes correlates with the level of G6PD enzyme activity present in red blood cells.
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Description
Test your knowledge on glutathione peroxidase, a selenium-dependent enzyme important for reducing hydrogen peroxide. This quiz covers its function, structure, and role in oxidative stress. Perfect for students of biochemistry and cell biology.
