ENV MED - KINETICS, QUIZ 3 (WK 4) EXAMS WITH 100%
CORRECT VERIFIED ANSWERS UPDATED 2025/2026 BEST
GRADED A+ FOR SUCCESS
Biotransformation has nothing to do with the metabolic conversion of endogenous and
exogenous chemicals from more lipid soluble (absorbable, retainable) to more water-soluble
(transportable, excretable) compounds
False
True CORRECT ANSWERS
False
Phase II reactions involve hydrolysis, reduction, and oxidation. These reactions usually result in
only a small increase in hydrophilicity (tendency to dissolve in water); the goal is to expose or
introduce a functional group (--OH, --NH2, --SH, or –COOH) that is then acted upon in Phase I.
Phase I biotransformation reactions include glucuronidation, sulfonation (more commonly
called sulfation), acetylation, methylation, and conjugation with glutathione or an amino acid
(usually glycine, taurine, or glutamic acid) which usually results in greatly increased
hydrophilicity, transportability, and elimination.
Much of this is true, but there's a major mix up of I and II that is backwards.
True CORRECT ANSWERS
Much of this is true, but there's a major mix up of I and II that is backwards.
Human individuals vary in our ability to biotransform (detoxify) a particular potential poison.
One person may have an enzyme (whose job it is to biotransform a toxin) that is altered from
normal in structure, or a reduced ability to make the enzyme in adequate quantity. Or, one
person may not have enough of the requisite nutrient cofactors to support the enzyme's
function (e.g. could lack adequate methyl group donors, or vitamin B6, or sulfur donors). All of
this gives rise to one of the principal reasons different individuals have different tolerances for a
given poison: A biosystem that biotransforms and excretes a poison well will be less likely to
accumulate that poison to the point of toxicity. The cofactors of normal, efficient
biotransforming enzyme function can come from a healthy diet.
True
False CORRECT ANSWERS
True
, ENV MED - KINETICS, QUIZ 3 (WK 4) EXAMS WITH 100%
CORRECT VERIFIED ANSWERS UPDATED 2025/2026 BEST
GRADED A+ FOR SUCCESS
The following is/are true about how and where in our bodies toxins are biotransformed:
- Biotransformational enzymes are located and do their work primarily in the smooth
Endoplasmic Reticulum (microsomal) and in the cytosol (fluid portion of cytoplasm); they are
located in lesser amounts in mitochondria, nuclei, and lysosomes.
- Often a single toxin goes through a series of 2-3 Phase I reactions before it is ready for Phase
II, and these may occur in different parts of the cell (e.g. microsomes → cytosol → lysosomes →
Phase II), increasing opportunities for a toxic intermediate to encounter a target molecule and
have a toxic effect during the transitions (see below).
- Biotransforming enzymes are present in virtually all tissues, are most concentrated in the liver,
next most in skin, lung, nasal mucosa, kidney, eye, and GI mucosa.
- Intestinal microflora play various roles in biotransformation. For one, they can
de- CORRECT ANSWERS
All of these statements are true about how and where in our bodies toxins are biotransformed.
Phase I enzymes and their substrates and end products include:
- Except for the enzymes of sulfonation, which is a Phase II system, all of these are Phase I
enzymes and their substrates or end products
- the cytochrome p450 system, with it's myriad enzymes and substrates
- Monoamine oxidase and epinephrine, norepinephrine, and serotonin
- enzymes of sulfonation
- xanthine oxidase, purines and uric acid CORRECT ANSWERS
Except for the enzymes of sulfonation, which is a Phase II system, all of these are Phase I
enzymes and their substrates or end products
One Phase II pathway is glucuronidation, in which a glucose-like carboxylic acid -- glucuronic
acid, is enzymatically attached to a potentially toxic waste material to make it more water
soluble (hydrophilic) and excretable. The following is true of such glucuronidation reactions:
- substrates (molecules that are acted upon) include many medical drugs, and many
environmental chemicals
- some waste steroid molecules are glucuronidated in the liver for excretion, including
estrogens, making hepatic glucuronidation a necessary function for maintaining normal blood
level of estrogens.
CORRECT VERIFIED ANSWERS UPDATED 2025/2026 BEST
GRADED A+ FOR SUCCESS
Biotransformation has nothing to do with the metabolic conversion of endogenous and
exogenous chemicals from more lipid soluble (absorbable, retainable) to more water-soluble
(transportable, excretable) compounds
False
True CORRECT ANSWERS
False
Phase II reactions involve hydrolysis, reduction, and oxidation. These reactions usually result in
only a small increase in hydrophilicity (tendency to dissolve in water); the goal is to expose or
introduce a functional group (--OH, --NH2, --SH, or –COOH) that is then acted upon in Phase I.
Phase I biotransformation reactions include glucuronidation, sulfonation (more commonly
called sulfation), acetylation, methylation, and conjugation with glutathione or an amino acid
(usually glycine, taurine, or glutamic acid) which usually results in greatly increased
hydrophilicity, transportability, and elimination.
Much of this is true, but there's a major mix up of I and II that is backwards.
True CORRECT ANSWERS
Much of this is true, but there's a major mix up of I and II that is backwards.
Human individuals vary in our ability to biotransform (detoxify) a particular potential poison.
One person may have an enzyme (whose job it is to biotransform a toxin) that is altered from
normal in structure, or a reduced ability to make the enzyme in adequate quantity. Or, one
person may not have enough of the requisite nutrient cofactors to support the enzyme's
function (e.g. could lack adequate methyl group donors, or vitamin B6, or sulfur donors). All of
this gives rise to one of the principal reasons different individuals have different tolerances for a
given poison: A biosystem that biotransforms and excretes a poison well will be less likely to
accumulate that poison to the point of toxicity. The cofactors of normal, efficient
biotransforming enzyme function can come from a healthy diet.
True
False CORRECT ANSWERS
True
, ENV MED - KINETICS, QUIZ 3 (WK 4) EXAMS WITH 100%
CORRECT VERIFIED ANSWERS UPDATED 2025/2026 BEST
GRADED A+ FOR SUCCESS
The following is/are true about how and where in our bodies toxins are biotransformed:
- Biotransformational enzymes are located and do their work primarily in the smooth
Endoplasmic Reticulum (microsomal) and in the cytosol (fluid portion of cytoplasm); they are
located in lesser amounts in mitochondria, nuclei, and lysosomes.
- Often a single toxin goes through a series of 2-3 Phase I reactions before it is ready for Phase
II, and these may occur in different parts of the cell (e.g. microsomes → cytosol → lysosomes →
Phase II), increasing opportunities for a toxic intermediate to encounter a target molecule and
have a toxic effect during the transitions (see below).
- Biotransforming enzymes are present in virtually all tissues, are most concentrated in the liver,
next most in skin, lung, nasal mucosa, kidney, eye, and GI mucosa.
- Intestinal microflora play various roles in biotransformation. For one, they can
de- CORRECT ANSWERS
All of these statements are true about how and where in our bodies toxins are biotransformed.
Phase I enzymes and their substrates and end products include:
- Except for the enzymes of sulfonation, which is a Phase II system, all of these are Phase I
enzymes and their substrates or end products
- the cytochrome p450 system, with it's myriad enzymes and substrates
- Monoamine oxidase and epinephrine, norepinephrine, and serotonin
- enzymes of sulfonation
- xanthine oxidase, purines and uric acid CORRECT ANSWERS
Except for the enzymes of sulfonation, which is a Phase II system, all of these are Phase I
enzymes and their substrates or end products
One Phase II pathway is glucuronidation, in which a glucose-like carboxylic acid -- glucuronic
acid, is enzymatically attached to a potentially toxic waste material to make it more water
soluble (hydrophilic) and excretable. The following is true of such glucuronidation reactions:
- substrates (molecules that are acted upon) include many medical drugs, and many
environmental chemicals
- some waste steroid molecules are glucuronidated in the liver for excretion, including
estrogens, making hepatic glucuronidation a necessary function for maintaining normal blood
level of estrogens.
