Introductory Toxicology Quiz

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Questions and Answers

What is the initial product formed when a free electron is passed to another unsaturated lipid?

Aldehydes

Lipid peroxide

Peroxyl radical (correct)

Reactive oxygen species

What is one of the critical mechanisms by which toxicants disrupt cell function?

Increase in mitochondrial energy output

Controlled ion pump activity

ATP depletion (correct)

Enhanced oxidative phosphorylation

How do some small molecules or ions inhibit proper function of proteins?

By enhancing their activity

By binding to reactive sites (correct)

By acting as ATP substitutes

By forming new proteins

What effect does the overproduction of reactive oxygen species (ROS) have on cells?

Fosters apoptosis (A) Signup and view all the answers

What process occurs in the mitochondria to produce ATP in the presence of oxygen?

TCA cycle and oxidative phosphorylation (B) Signup and view all the answers

What happens when an ion channel remains open due to the action of a toxicant like DDT?

Disrupted ion homeostasis (B) Signup and view all the answers

What is the primary role of ATP in maintaining cell function?

To drive ion pumps for homeostasis (C) Signup and view all the answers

What can be a consequence of altering the function of target molecules by toxicants?

Dysregulation of cellular function (A) Signup and view all the answers

What must occur for a toxic effect to manifest after a toxicant interacts with a cell or tissue?

The toxicant must reach a sufficient concentration at the cellular target. (C) Signup and view all the answers

Which of the following describes a mechanism by which toxicity can occur?

Inhibition of normal cellular processes. (C) Signup and view all the answers

What is meant by 'toxication' in the context of mechanisms of toxicity?

Biotransformation that increases toxicity. (C) Signup and view all the answers

What effect can a toxicant have on target molecules?

They can lead to neoantigen formation due to mutations. (B) Signup and view all the answers

How can a toxicant alter the biological microenvironment of a cell?

By occupying essential cellular sites. (C) Signup and view all the answers

Alterations in gene expression due to toxicant exposure can lead to what kind of outcome?

Increased likelihood of cellular dysfunction. (C) Signup and view all the answers

What is one of the roles of detoxication in toxicity management?

To prevent formation or eliminate a toxic metabolite. (D) Signup and view all the answers

Which of the following is a factor that could increase delivery of a toxicant to its target?

High cellular receptor affinity. (D) Signup and view all the answers

What is the main consequence of TFM accumulation in the tissues of sea lamprey?

Necrosis due to energy depletion (D) Signup and view all the answers

What major consequence follows ATP depletion in a cell?

Failure to maintain homeostasis (A) Signup and view all the answers

What is a potential harmful outcome of inappropriate repair mechanisms?

Development of tissue necrosis (B) Signup and view all the answers

Which of the following can occur due to increased cytosolic calcium levels?

Activation of hydrolytic enzymes (C) Signup and view all the answers

Which of the following describes a mechanism of adaptation?

Increased sequestration by intracellular binding proteins (A) Signup and view all the answers

How does high Ca2+ levels in mitochondria contribute to free radical formation?

By increasing electron flow to oxygen or nitrogen (A) Signup and view all the answers

Which situation represents a failure of repair mechanisms?

Repair mechanisms becoming overwhelmed or exhausted (A) Signup and view all the answers

What role do chaperones play during the repair process?

Aid in the repair of misfolded proteins (A) Signup and view all the answers

What is the principal effect of ATP depletion on the endoplasmic reticulum?

It deprives calcium pumps of necessary fuel (D) Signup and view all the answers

What leads to the destabilization of the cytoskeleton in a cell experiencing high levels of cytosolic calcium?

Elevated Ca2+ concentration (A) Signup and view all the answers

Carcinogenesis is primarily caused by which of the following?

Uncontrolled cell division (D) Signup and view all the answers

What is one of the risks of prolonged adaptive mechanisms?

Increased toxicity (B) Signup and view all the answers

How does the overproduction of reactive oxygen species (ROS) affect calcium pumping mechanisms?

It can impact pumps that normally regulate calcium levels (B) Signup and view all the answers

What is the effect of sustained elevated [Ca2+] on ATP production?

It depletes ATP levels (A) Signup and view all the answers

Which of the following describes a repair mechanism?

Reversal of chemical alterations (D) Signup and view all the answers

What is the main determinant for a cell undergoing necrosis versus apoptosis?

The extent of mitochondrial damage (A) Signup and view all the answers

What role does the mitochondrial membrane potential play in ATP synthesis?

It is crucial for H+ separation contributing to ATP synthesis (A) Signup and view all the answers

What role does Cytochrome C play in the process of apoptosis?

It activates executioner caspases. (B) Signup and view all the answers

What role do tumor suppressor genes play in cell regulation?

They signal DNA repair or prevent cell cycle progression. (A), They trigger apoptosis in damaged cells. (B) Signup and view all the answers

What happens during mitochondrial permeability transition (MPT)?

There is an increase in inner mitochondrial membrane permeability. (B) Signup and view all the answers

How can a mutation in an oncogene lead to cancer?

By altering its regulation to promote excessive cell division. (C) Signup and view all the answers

Which statement is true regarding mutagens and carcinogens?

Not all mutagens affect critical genes related to cancer. (D) Signup and view all the answers

What initiates necrosis at a cellular level?

Depletion of ATP levels (D) Signup and view all the answers

What leads to cellular leakage of ions and damage to membranes?

Direct damage from ROS and RNS species (C) Signup and view all the answers

What can increase the likelihood of cellular mutations during DNA replication?

Presence of toxicants that kill cells. (B) Signup and view all the answers

What are the consequences of DNA adducts formed by mutagens?

They can introduce mutations during the repair process. (C) Signup and view all the answers

What is the outcome of excessive free radicals released into the cytosol?

Cell membrane permeability changes (B) Signup and view all the answers

What natural process causes programmed cell death?

Apoptosis (A) Signup and view all the answers

What is the fundamental difference between an initiated cell and a normal cell?

Initiated cells contain acquired mutations. (D) Signup and view all the answers

What is the consequence of TFM being detoxified in fishes?

Conversion to less harmful compounds (D) Signup and view all the answers

How can directly damaging DNA lead to cancer development?

By fostering mutations that can accumulate over time. (C) Signup and view all the answers

What is a primary characteristic of the transition from focal lesion to full-on cancer?

It is irreversible and progresses over time. (B) Signup and view all the answers

Study Notes

Introductory Toxicology: Cellular and Tissue Targets of Toxicity

A toxicant interacts with a tissue or cell to cause a toxic effect.
This effect only occurs if the toxicant reaches a sufficient concentration at the cellular target.
Mechanisms of toxicity are simplified into four steps: Toxicokinetics, Interaction with target (or microenvironment), Progression to cellular dysfunction, and Inappropriate repair.

Toxicokinetics

Exposure: This includes absorption, distribution and metabolism of toxicants, storage of toxicants, and excretion.
Factors that decrease delivery to the target include presystemic elimination, distribution away from the target, excretion, and detoxication.
Factors that increase delivery to the target include absorption, distribution to the target, and reabsorption.
Biotransformation: This process can increase or decrease toxicity (metabolic activation). Detoxication prevents the formation or removes toxic metabolites

Interaction with Target

Interaction between the toxicant (T) and target molecule (M) can result in an altered target molecule.
Interaction occurs in several levels: Molecular level, Cellular level, Organ level and Organism level
Adverse effects that occur in a particular order include alteration of molecular targets, cellular responses then an overall organism response.

Progression to Cellular Dysfunction

Toxicants can alter gene expression by directly affecting certain genes through activating transcription factors.
Toxicants bind to certain membrane receptors, leading to signaling pathways, resulting in altered gene expression.
Some toxicants cause oxidative stress, which is due to reactive oxygen species (ROS). Reactive oxygen species are examples of superoxide.
Our cells have mechanisms to remove the ROS.
Lipid peroxidation can occur from ROS causing damage to lipids and forming lipid radicals.

Inappropriate Repair and Adaptation

Molecular repair: involves repairing proteins, lipids, and DNA. Reversal of chemical alterations helps this process. Removal of damaged cells helps by replacing with new synthesized units.
Cellular repair involves repairing cell organelles, repairing damaged axons, and regeneration.
Tissue repair includes deletion of injured cells, leading to tissue regeneration through proliferation.
Repair mechanisms can become overwhelmed causing impaired repair leading to toxicity.

Cellular Dysfunction Examples

ATP depletion is a crucial part of cellular dysfunction. Toxicants that interfere with aerobic metabolism will lead to decreasing ATP levels in cells. This impacts active transporters (ion pumps). Cells may lose the ability to maintain homeostasis. Toxicants can cause high levels of calcium in the cells and can disrupt the cytoskeleton.
Overproduction of ROS (Reactive Oxygen Species) and RNS (Reactive Nitrogen Species), resulting from inhibited ATP synthase or caused by calcium. These impact cellular function by damaging membranes, causing ion leakage, and further reducing ATP reserves hindering cellular function.

Carcinogenesis

Cell division is highly regulated.
Cancer results from uncontrolled cell division due to mutations in genes that normally signal the cell for cell cycle progression or mutations in genes that block cell cycle progression or signal DNA repair.
Oncogenes lead to cell cycle progression in cancer while tumour suppressors genes stop the cell cycle.
Mutagens can cause cancers by either directly damaging or binding to DNA leading to mutations in the DNA base sequence.

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Description

Test your knowledge on the cellular targets and mechanisms of toxicity in toxicology. This quiz covers essential concepts such as toxicokinetics, biotransformation, and the interplay between toxicants and biological systems. Understand how toxicants interact with cells and the progression of toxicity in tissues.