Toxicokinetics II: Biotransformation of Toxicants

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What is the primary function of biotransformation in an organism?

To enhance the elimination and detoxification of chemicals (correct)

To increase the storage of toxicants in the body

To convert hydrophilic molecules to hydrophobic molecules

To decrease the polarity of lipophilic compounds

What is the result of Phase I metabolism in xenobiotic metabolism?

Increased biological activity of metabolites

Decreased polarity of metabolites

Increased excretability of metabolites (correct)

Increased water solubility of metabolites

What is the primary location of biotransformation reactions within the cell?

Mitochondria

Endoplasmic reticulum

Cytoplasm (correct)

Nucleus

What is the effect of storage on the body's ability to biotransform and eliminate toxicants?

It affects the body's ability to biotransform and eliminate toxicants Signup and view all the answers

What is the term for the 'build-up' process of biochemical reactions in metabolism?

Anabolism Signup and view all the answers

What is the primary purpose of Phase II metabolism in xenobiotic metabolism?

To increase the excretability of metabolites Signup and view all the answers

What is the result of biotransformation on the fate of lipophilic compounds in the body?

They become more hydrophilic Signup and view all the answers

What is the term for the process of converting chemicals to less toxic forms in biotransformation?

Detoxification Signup and view all the answers

What is the primary route of elimination of hydrophilic metabolites in the body?

Kidneys Signup and view all the answers

What is the primary goal of the detoxification process?

To convert toxicants into more water-soluble forms Signup and view all the answers

What is the main site of biotransformation in the body?

Liver Signup and view all the answers

What is the result of Phase I reactions in biotransformation?

Increase in hydrophilicity Signup and view all the answers

What is the purpose of biotransformation in the body?

To terminate the biological activity of chemicals Signup and view all the answers

What is the result of some chemicals being partially converted to more toxic products?

Increased toxicity of the parent substance Signup and view all the answers

What is the role of cytochrome P450 in biotransformation?

To add or unmask reactive side groups Signup and view all the answers

What is the primary mechanism for eliminating toxicants from the body?

Excretion through urine and feces Signup and view all the answers

What is the result of Phase II reactions in biotransformation?

Conjugation of reactive side groups Signup and view all the answers

What is the main organ responsible for the elimination of toxicants through excretion?

Kidney Signup and view all the answers

What is the primary effect of the oxidation reaction in Phase I metabolism?

Addition of oxygen and removal of hydrogen Signup and view all the answers

What is the role of the enzyme alcohol dehydrogenase in Phase I metabolism?

To catalyze oxidation reactions Signup and view all the answers

What is the effect of CYP450 enzyme induction on the metabolism of toxicants?

It increases the bioactivation of toxicants Signup and view all the answers

What is the primary function of the P450 system in Phase I metabolism?

To bioactivate non-toxic compounds Signup and view all the answers

What is the role of glutathione in the metabolism of paracetamol?

To conjugate with the reactive metabolite NAPQI Signup and view all the answers

What is the effect of a paracetamol overdose on the metabolism of NAPQI?

Conjugation with glutathione becomes saturated, leading to increased hepatocyte damage Signup and view all the answers

What is the effect of CYP450 enzyme induction on the composition of P450 enzymes?

It causes a marked increase (>20-fold) in the composition of P450 enzymes Signup and view all the answers

What is the role of esterases in Phase I metabolism?

To catalyze hydrolysis reactions Signup and view all the answers

What is the effect of rifampin on the expression of CYP450 enzymes?

It induces the expression of CYP3A Signup and view all the answers

What is the effect of induction on the therapeutic effect of drugs?

It decreases the therapeutic effect of drugs Signup and view all the answers

What is the role of P450 in biotransformation?

It is a phase I reaction enzyme that can be induced by toxicants Signup and view all the answers

What is the effect of conjugation reactions on molecular size and polarity?

It increases molecular size and polarity Signup and view all the answers

What is the role of CYP2E1 in the metabolism of vinyl chloride?

It converts vinyl chloride to chloroethylene oxide Signup and view all the answers

What is the effect of chronic low-level exposure to aflatoxins?

It increases the risk of liver cancer Signup and view all the answers

How does oltipraz prevent AFB1 toxicity?

It inhibits CYP450 and induces GST Signup and view all the answers

What is the result of biotransformation reactions?

It increases the polarity of compounds and decreases toxicity via metabolism of a toxic parent compound Signup and view all the answers

What is the role of CYP3A4 in the metabolism of aflatoxin B1?

It bioactivates aflatoxin B1 to its epoxide form Signup and view all the answers

What is the effect of induction on tolerance to toxicants?

It increases tolerance to some toxicants while enhancing the toxicity of others Signup and view all the answers