NRCC Toxicological Chemist Exam
1. What type of bond is formed by the sharing of electron pairs between atoms?
A. Ionic bond
B. Covalent bond
C. Hydrogen bond
D. Metallic bond
Answer: B. Covalent bond
Explanation: Covalent bonds involve the sharing of electrons between atoms, which is
fundamental in molecular formation.
2. Which of the following best describes a Lewis acid?
A. Electron pair donor
B. Electron pair acceptor
C. Proton donor
D. Proton acceptor
Answer: B. Electron pair acceptor
Explanation: A Lewis acid accepts an electron pair from a Lewis base during bond
formation.
3. What type of reaction is represented by A + B → AB + heat?
A. Endothermic
B. Exothermic
C. Photochemical
D. Equilibrium reaction
Answer: B. Exothermic
Explanation: The release of heat indicates an exothermic reaction where energy is released.
4. Which compound is a common reducing agent?
A. KMnO₄
B. KBrO₃
C. NaBH₄
D. H₂SO₄
Answer: C. NaBH₄
Explanation: Sodium borohydride (NaBH₄) is a powerful reducing agent used to donate
hydrogen atoms in reactions.
5. The pH of a solution measures:
A. The concentration of hydrogen ions
B. The concentration of sodium ions
C. The concentration of oxygen
D. The pKa of the acid
Answer: A. The concentration of hydrogen ions
Explanation: pH quantifies the acidity or basicity by measuring hydrogen ion concentration.
6. Which enzyme is crucial for the metabolism of acetaminophen into its toxic
metabolite?
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, NRCC Toxicological Chemist Exam
A. Alcohol dehydrogenase
B. Cytochrome P450 2E1
C. Acetylcholinesterase
D. Monoamine oxidase
Answer: B. Cytochrome P450 2E1
Explanation: CYP2E1 metabolizes acetaminophen into the reactive metabolite NAPQI,
which can cause liver damage if not detoxified.
7. Glutathione is important in detoxification because it:
A. Catalyzes lipid oxidation
B. Binds to toxic electrophilic compounds
C. Generates free radicals
D. Serves as a coenzyme for ATP production
Answer: B. Binds to toxic electrophilic compounds
Explanation: Glutathione conjugates with toxic substances, making them more water-soluble
for excretion.
8. The cytochrome P450 system primarily functions in:
A. Digestive enzyme production
B. Phase I metabolism of xenobiotics
C. Protein synthesis
D. Cellular respiration
Answer: B. Phase I metabolism of xenobiotics
Explanation: Cytochrome P450 enzymes oxidize xenobiotics during phase I metabolism to
increase their solubility.
9. Biotransformation of xenobiotics generally involves:
A. Phase I: Conjugation reactions
B. Phase II: Oxidation, reduction, and hydrolysis
C. Phase I: Oxidation, reduction, and hydrolysis
D. Phase III: Transport outside the cell
Answer: C. Phase I: Oxidation, reduction, and hydrolysis
Explanation: Phase I reactions introduce functional groups through oxidation, reduction, and
hydrolysis, preparing compounds for phase II conjugation.
10. Which cofactor is essential for alcohol dehydrogenase activity?
A. NAD⁺
B. FAD
C. Coenzyme A
D. Tetrahydrofolate
Answer: A. NAD⁺
Explanation: Alcohol dehydrogenase uses NAD⁺ as a cofactor to oxidize ethanol to
acetaldehyde.
11. The blood-brain barrier protects the brain from:
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, NRCC Toxicological Chemist Exam
A. High oxygen levels
B. Toxic substances and pathogens
C. Glucose
D. Normal ions
Answer: B. Toxic substances and pathogens
Explanation: The blood-brain barrier limits entry of harmful substances into the brain,
maintaining neural homeostasis.
12. Which organ is primarily responsible for the detoxification of chemicals?
A. Heart
B. Kidney
C. Liver
D. Lung
Answer: C. Liver
Explanation: The liver contains enzymes like cytochrome P450 to metabolize and detoxify
many xenobiotics.
13. Phase II reactions in the liver primarily occur in which cellular organelle?
A. Mitochondria
B. Nucleus
C. Endoplasmic reticulum
D. Cytosol
Answer: D. Cytosol
Explanation: Many phase II conjugation reactions occur in the cytosol where conjugating
enzymes like GST are located.
14. Which of the following is a common toxic effect of heavy metals like lead on the
human body?
A. Enhanced cognitive function
B. Anemia due to interference with heme synthesis
C. Increased bone density
D. Improved kidney function
Answer: B. Anemia due to interference with heme synthesis
Explanation: Lead interferes with enzymes in heme synthesis, leading to anemia and other
neurological effects.
15. The term “bioavailability” refers to:
A. The amount of a substance absorbed and available at the site of action
B. The potency of a drug
C. The molecular weight of a substance
D. The metabolic rate of a substance
Answer: A. The amount of a substance absorbed and available at the site of action
Explanation: Bioavailability measures the fraction of an administered dose that reaches
systemic circulation unchanged.
16. What effect does electron-donating substituent have on the reactivity of an aromatic
ring in electrophilic aromatic substitution?
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, NRCC Toxicological Chemist Exam
A. Decreases reactivity
B. Increases reactivity
C. No effect
D. Makes ring inert
Answer: B. Increases reactivity
Explanation: Electron-donating groups enhance the electron density on the aromatic ring,
making it more reactive towards electrophiles.
17. The rate of a chemical reaction is most influenced by:
A. The stoichiometric coefficients
B. The activation energy
C. The color of reactants
D. The size of the flask
Answer: B. The activation energy
Explanation: Lower activation energy typically results in a faster reaction rate as fewer
energy barriers exist.
18. In a polar solvent, which type of reaction mechanism is generally favored?
A. SN1
B. SN2
C. E2
D. Free radical
Answer: A. SN1
Explanation: Polar solvents stabilize carbocations, making SN1 reactions more favorable
compared to SN2 which prefer polar aprotic solvents.
19. A catalyst:
. Increases the activation energy
B. Decreases the activation energy
C. Changes the reaction equilibrium
D. Is consumed in the reaction
Answer: B. Decreases the activation energy
Explanation: Catalysts provide an alternative reaction pathway with lower activation energy,
speeding up the reaction without being consumed.
20. What is the primary characteristic of an amphiprotic substance?
A. Only accepts protons
B. Only donates protons
C. Can both donate and accept protons
D. Neither donates nor accepts protons
Answer: C. Can both donate and accept protons
Explanation: Amphiprotic substances, like HCO₃⁻, can act as both acids and bases
depending on the environment.
21. The primary function of the citric acid cycle is to:
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1. What type of bond is formed by the sharing of electron pairs between atoms?
A. Ionic bond
B. Covalent bond
C. Hydrogen bond
D. Metallic bond
Answer: B. Covalent bond
Explanation: Covalent bonds involve the sharing of electrons between atoms, which is
fundamental in molecular formation.
2. Which of the following best describes a Lewis acid?
A. Electron pair donor
B. Electron pair acceptor
C. Proton donor
D. Proton acceptor
Answer: B. Electron pair acceptor
Explanation: A Lewis acid accepts an electron pair from a Lewis base during bond
formation.
3. What type of reaction is represented by A + B → AB + heat?
A. Endothermic
B. Exothermic
C. Photochemical
D. Equilibrium reaction
Answer: B. Exothermic
Explanation: The release of heat indicates an exothermic reaction where energy is released.
4. Which compound is a common reducing agent?
A. KMnO₄
B. KBrO₃
C. NaBH₄
D. H₂SO₄
Answer: C. NaBH₄
Explanation: Sodium borohydride (NaBH₄) is a powerful reducing agent used to donate
hydrogen atoms in reactions.
5. The pH of a solution measures:
A. The concentration of hydrogen ions
B. The concentration of sodium ions
C. The concentration of oxygen
D. The pKa of the acid
Answer: A. The concentration of hydrogen ions
Explanation: pH quantifies the acidity or basicity by measuring hydrogen ion concentration.
6. Which enzyme is crucial for the metabolism of acetaminophen into its toxic
metabolite?
1
, NRCC Toxicological Chemist Exam
A. Alcohol dehydrogenase
B. Cytochrome P450 2E1
C. Acetylcholinesterase
D. Monoamine oxidase
Answer: B. Cytochrome P450 2E1
Explanation: CYP2E1 metabolizes acetaminophen into the reactive metabolite NAPQI,
which can cause liver damage if not detoxified.
7. Glutathione is important in detoxification because it:
A. Catalyzes lipid oxidation
B. Binds to toxic electrophilic compounds
C. Generates free radicals
D. Serves as a coenzyme for ATP production
Answer: B. Binds to toxic electrophilic compounds
Explanation: Glutathione conjugates with toxic substances, making them more water-soluble
for excretion.
8. The cytochrome P450 system primarily functions in:
A. Digestive enzyme production
B. Phase I metabolism of xenobiotics
C. Protein synthesis
D. Cellular respiration
Answer: B. Phase I metabolism of xenobiotics
Explanation: Cytochrome P450 enzymes oxidize xenobiotics during phase I metabolism to
increase their solubility.
9. Biotransformation of xenobiotics generally involves:
A. Phase I: Conjugation reactions
B. Phase II: Oxidation, reduction, and hydrolysis
C. Phase I: Oxidation, reduction, and hydrolysis
D. Phase III: Transport outside the cell
Answer: C. Phase I: Oxidation, reduction, and hydrolysis
Explanation: Phase I reactions introduce functional groups through oxidation, reduction, and
hydrolysis, preparing compounds for phase II conjugation.
10. Which cofactor is essential for alcohol dehydrogenase activity?
A. NAD⁺
B. FAD
C. Coenzyme A
D. Tetrahydrofolate
Answer: A. NAD⁺
Explanation: Alcohol dehydrogenase uses NAD⁺ as a cofactor to oxidize ethanol to
acetaldehyde.
11. The blood-brain barrier protects the brain from:
2
, NRCC Toxicological Chemist Exam
A. High oxygen levels
B. Toxic substances and pathogens
C. Glucose
D. Normal ions
Answer: B. Toxic substances and pathogens
Explanation: The blood-brain barrier limits entry of harmful substances into the brain,
maintaining neural homeostasis.
12. Which organ is primarily responsible for the detoxification of chemicals?
A. Heart
B. Kidney
C. Liver
D. Lung
Answer: C. Liver
Explanation: The liver contains enzymes like cytochrome P450 to metabolize and detoxify
many xenobiotics.
13. Phase II reactions in the liver primarily occur in which cellular organelle?
A. Mitochondria
B. Nucleus
C. Endoplasmic reticulum
D. Cytosol
Answer: D. Cytosol
Explanation: Many phase II conjugation reactions occur in the cytosol where conjugating
enzymes like GST are located.
14. Which of the following is a common toxic effect of heavy metals like lead on the
human body?
A. Enhanced cognitive function
B. Anemia due to interference with heme synthesis
C. Increased bone density
D. Improved kidney function
Answer: B. Anemia due to interference with heme synthesis
Explanation: Lead interferes with enzymes in heme synthesis, leading to anemia and other
neurological effects.
15. The term “bioavailability” refers to:
A. The amount of a substance absorbed and available at the site of action
B. The potency of a drug
C. The molecular weight of a substance
D. The metabolic rate of a substance
Answer: A. The amount of a substance absorbed and available at the site of action
Explanation: Bioavailability measures the fraction of an administered dose that reaches
systemic circulation unchanged.
16. What effect does electron-donating substituent have on the reactivity of an aromatic
ring in electrophilic aromatic substitution?
3
, NRCC Toxicological Chemist Exam
A. Decreases reactivity
B. Increases reactivity
C. No effect
D. Makes ring inert
Answer: B. Increases reactivity
Explanation: Electron-donating groups enhance the electron density on the aromatic ring,
making it more reactive towards electrophiles.
17. The rate of a chemical reaction is most influenced by:
A. The stoichiometric coefficients
B. The activation energy
C. The color of reactants
D. The size of the flask
Answer: B. The activation energy
Explanation: Lower activation energy typically results in a faster reaction rate as fewer
energy barriers exist.
18. In a polar solvent, which type of reaction mechanism is generally favored?
A. SN1
B. SN2
C. E2
D. Free radical
Answer: A. SN1
Explanation: Polar solvents stabilize carbocations, making SN1 reactions more favorable
compared to SN2 which prefer polar aprotic solvents.
19. A catalyst:
. Increases the activation energy
B. Decreases the activation energy
C. Changes the reaction equilibrium
D. Is consumed in the reaction
Answer: B. Decreases the activation energy
Explanation: Catalysts provide an alternative reaction pathway with lower activation energy,
speeding up the reaction without being consumed.
20. What is the primary characteristic of an amphiprotic substance?
A. Only accepts protons
B. Only donates protons
C. Can both donate and accept protons
D. Neither donates nor accepts protons
Answer: C. Can both donate and accept protons
Explanation: Amphiprotic substances, like HCO₃⁻, can act as both acids and bases
depending on the environment.
21. The primary function of the citric acid cycle is to:
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