Toxicology Exam 2 with Complete
Solutions
• xenobiotic - a foreign chemical substance. Metabolism (i.e., biotransformation) applies
to endogenous chemicals as well - ANSWER-Phase I
General
• include microsomal mono-oxygenations, cytosolic and mitochondrial oxidations
• All of these reactions, with the exception of reductions, introduce polar groups to the
molecule that, in most cases, can be conjugated during phase II metabolism.
o Phase I reactions are functionalization reactions
adding a new oxygen atom (e.g. -OH group) (polar groups)
exposing an existing functional group (e.g. hydrolysis of ester linkage)
functionalization = introduction of a new functional group)
A dose - ANSWER-an amount of chemical
A primary active transport - ANSWER-process is one in which molecules move through
transport proteins that have been activated by ATP
A Threshold dose - ANSWER-a dose, below which no effect is observed or measured.
Absorption and Distribution of Toxicants - ANSWER-Absorption->Distribution-
>Metabolism->Elimination
Aflatoxin B1 - ANSWER-an aflatoxin produced by Aspergillus flavus and A. parasiticus.
It is an incredibly potent carcinogen with a TD50 0.0032 mg/kg/day in rats.[1] This
carcinogenic potency varies across species with some, such as rats, seemingly much
more susceptible than others, such as monkeys.[2] Aflatoxin B1 is a common
contaminant in a variety of foods including peanuts, cottonseed meal, corn, and other
grains;[3] as well as animal feeds.
Amino acids are filtered out of the blood in the glomerulus of the kidney, but amino
acids are not a waste product. The body needs the amino acids, so they are reabsorbed
from the filtrate back into the tubule cells of the kidney. After the amino acids are
concentrated in the tubule cells they must be transported back into blood. What type of
transport is used to move the amino acids from the filtrate to the inside of the kidney
cells? - ANSWER-active transport:
Amino acids are moved into the kidney cells using secondary active transport. They are
being moved against a concentration gradient from an area of low concentration to an
area of high concentration.
, An effective dose - ANSWER-a dose (above threshold) that produces the desired effect.
An epoxide - ANSWER-a cyclic ether with a three-atom ring. This ring approximates an
equilateral triangle, which makes it strained, and hence highly reactive, more so than
other ethers. They are produced on a large scale for many applications. In general, low
molecular weight epoxides are colourless and nonpolar, and often volatile
apoptosis - ANSWER-the death of cells that occurs as a normal and controlled part of
an organism's growth or development.
Bottom line: - ANSWER-A soluble gas will keep entering tissues until it becomes
saturated at this point the pressure in the tissues pushes back against the pressure in
the lungs (atmosphere). A non-soluble gas does the same thing, but reaches (push
back or equilibrium) faster. Therefore less gas goes into the tissues.
Cisplatin - ANSWER-a chemotherapy medication used to treat a number of cancers.[1]
This includes testicular cancer, ovarian cancer, cervical cancer, breast cancer, bladder
cancer, head and neck cancer, esophageal cancer, lung cancer, mesothelioma, brain
tumors and neuroblastoma.[1] It is used by injection into a vein.
Determine the rate of diffusion (flux) for aspirin dissolving through the stomach lining.
C1= 50 mg/L and C2 = 290 mg/L.
The diffusivity constant of aspirin is 0.29×10-9 cm2/s
the thickness of the stomach lining is approximately 0.5 cm. - ANSWER-Using Fick's
first law:
J = -D(dc/dx)
Where:
J = unknown flux
D = 0.29×10-9 cm2/s
dc = (C1 - C2) = 50mg/L - 290mg/L = -240mg/L, which is equivalent to
-240mg/1000cm3 =-0.24mg/cm3
dx = 0.5cm
Facilitated diffusion - ANSWER-the process of spontaneous passive transport (as
opposed to active transport) of molecules or ions across a biological membrane via
specific transmembrane integral proteins.
Fick's 1st Law of Diffusion - ANSWER-Diffusion occurs in response to a concentration
gradient expressed as the change in concentration due to a change in position
Fick's 1st Law of Diffusion Formula - ANSWER-J = -D ΔC/Δd Where
J = # of molecules/ area(time) or moles / cm2 (s)
Solutions
• xenobiotic - a foreign chemical substance. Metabolism (i.e., biotransformation) applies
to endogenous chemicals as well - ANSWER-Phase I
General
• include microsomal mono-oxygenations, cytosolic and mitochondrial oxidations
• All of these reactions, with the exception of reductions, introduce polar groups to the
molecule that, in most cases, can be conjugated during phase II metabolism.
o Phase I reactions are functionalization reactions
adding a new oxygen atom (e.g. -OH group) (polar groups)
exposing an existing functional group (e.g. hydrolysis of ester linkage)
functionalization = introduction of a new functional group)
A dose - ANSWER-an amount of chemical
A primary active transport - ANSWER-process is one in which molecules move through
transport proteins that have been activated by ATP
A Threshold dose - ANSWER-a dose, below which no effect is observed or measured.
Absorption and Distribution of Toxicants - ANSWER-Absorption->Distribution-
>Metabolism->Elimination
Aflatoxin B1 - ANSWER-an aflatoxin produced by Aspergillus flavus and A. parasiticus.
It is an incredibly potent carcinogen with a TD50 0.0032 mg/kg/day in rats.[1] This
carcinogenic potency varies across species with some, such as rats, seemingly much
more susceptible than others, such as monkeys.[2] Aflatoxin B1 is a common
contaminant in a variety of foods including peanuts, cottonseed meal, corn, and other
grains;[3] as well as animal feeds.
Amino acids are filtered out of the blood in the glomerulus of the kidney, but amino
acids are not a waste product. The body needs the amino acids, so they are reabsorbed
from the filtrate back into the tubule cells of the kidney. After the amino acids are
concentrated in the tubule cells they must be transported back into blood. What type of
transport is used to move the amino acids from the filtrate to the inside of the kidney
cells? - ANSWER-active transport:
Amino acids are moved into the kidney cells using secondary active transport. They are
being moved against a concentration gradient from an area of low concentration to an
area of high concentration.
, An effective dose - ANSWER-a dose (above threshold) that produces the desired effect.
An epoxide - ANSWER-a cyclic ether with a three-atom ring. This ring approximates an
equilateral triangle, which makes it strained, and hence highly reactive, more so than
other ethers. They are produced on a large scale for many applications. In general, low
molecular weight epoxides are colourless and nonpolar, and often volatile
apoptosis - ANSWER-the death of cells that occurs as a normal and controlled part of
an organism's growth or development.
Bottom line: - ANSWER-A soluble gas will keep entering tissues until it becomes
saturated at this point the pressure in the tissues pushes back against the pressure in
the lungs (atmosphere). A non-soluble gas does the same thing, but reaches (push
back or equilibrium) faster. Therefore less gas goes into the tissues.
Cisplatin - ANSWER-a chemotherapy medication used to treat a number of cancers.[1]
This includes testicular cancer, ovarian cancer, cervical cancer, breast cancer, bladder
cancer, head and neck cancer, esophageal cancer, lung cancer, mesothelioma, brain
tumors and neuroblastoma.[1] It is used by injection into a vein.
Determine the rate of diffusion (flux) for aspirin dissolving through the stomach lining.
C1= 50 mg/L and C2 = 290 mg/L.
The diffusivity constant of aspirin is 0.29×10-9 cm2/s
the thickness of the stomach lining is approximately 0.5 cm. - ANSWER-Using Fick's
first law:
J = -D(dc/dx)
Where:
J = unknown flux
D = 0.29×10-9 cm2/s
dc = (C1 - C2) = 50mg/L - 290mg/L = -240mg/L, which is equivalent to
-240mg/1000cm3 =-0.24mg/cm3
dx = 0.5cm
Facilitated diffusion - ANSWER-the process of spontaneous passive transport (as
opposed to active transport) of molecules or ions across a biological membrane via
specific transmembrane integral proteins.
Fick's 1st Law of Diffusion - ANSWER-Diffusion occurs in response to a concentration
gradient expressed as the change in concentration due to a change in position
Fick's 1st Law of Diffusion Formula - ANSWER-J = -D ΔC/Δd Where
J = # of molecules/ area(time) or moles / cm2 (s)
