Toxic Effects of Metals

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Questions and Answers

What is the primary effect of lead exposure on the male reproductive system?

Testicular degeneration (correct)

Increased testosterone production

Leydig-cell hypertrophy

Spermatogenesis stimulation

Which metal-binding protein plays a crucial role in regulating the intracellular bioavailability of Cd, Cu, Hg, Zn, and Ag?

SH binding protein

Ligand

Cytosolic protein

Metallothionein (MT) (correct)

What is the duration of acute exposure to toxic heavy metals?

> 365 days

15-354 days

Variable duration

≤ 14 days (correct)

What is the primary characteristic of chronic exposure to toxic heavy metals?

Repeated/continuous exposure Signup and view all the answers

What is the term for arsenic combined with carbon and hydrogen?

Organic As Signup and view all the answers

What is a characteristic of white/colorless powders of arsenic?

They do not evaporate Signup and view all the answers

Which of the following is an example of chronic exposure to toxic heavy metals?

Contaminated food and water Signup and view all the answers

What is a source of arsenic release into the environment?

Manufacturing of chemicals and glasses Signup and view all the answers

What is the most toxic form of arsenic?

Arsine gas (AsH3) Signup and view all the answers

What is the term for the accumulation of toxic substances in the body?

Accumulation Signup and view all the answers

What is arsenic frequently referred to as?

A metal Signup and view all the answers

How do microorganisms in the environment affect arsenic compounds?

They convert arsenic compounds to dimethylarsenate Signup and view all the answers

Where can arsenic accumulate in the body?

In bone tissue Signup and view all the answers

What is a way arsenic distributes in the body?

Throughout the body within 24 hours of absorption Signup and view all the answers

What is a way arsenic affects the body?

It binds to SH groups of tissue protein Signup and view all the answers

What can happen to arsenic in the environment?

It can change its form or become attached to or separated from particles Signup and view all the answers

What is the primary mechanism of toxic effects of metals on the cellular target?

Interaction between free metal and specific biochemical processes Signup and view all the answers

What is the site of action for the toxic effects of metals on the nervous system?

Subcellular organelles Signup and view all the answers

Which of the following is a common mechanism of metal toxicity?

Enzyme inhibition Signup and view all the answers

What is the effect of metal interaction with sulfhydryl groups on enzymes?

Inhibition of enzymes Signup and view all the answers

What is the effect of Pb on the zinc-dependent enzyme δ-aminolevulinic acid dehydratase (ALAD)?

Inhibition of the enzyme Signup and view all the answers

What is the effect of metal interaction with subcellular organelles?

Disruption of the structure and function of organelles Signup and view all the answers

What is the effect of metal toxicity on the kidney?

Damage to kidney function Signup and view all the answers

What is the effect of some metals on carcinogenicity?

Induction of carcinogenicity Signup and view all the answers

What is one of the health effects of Cadmium?

Poor appetite Signup and view all the answers

What is the primary form of Mercury that is absorbed by the respiratory system?

Elemental mercury vapor Signup and view all the answers

What is the result of the degradation of CdMT complex?

Release of Cd2+ Signup and view all the answers

What is the primary location where Cadmium accumulates?

Lysosomes Signup and view all the answers

What is the primary route of exposure to Elemental mercury?

Inhalation Signup and view all the answers

What is the form of Mercury that is usually harmless when ingested?

Elemental mercury Signup and view all the answers

What is the result of Cadmium accumulation in the kidneys?

Kidney toxicity Signup and view all the answers

What is an example of a device that uses Mercury?

Thermometer Signup and view all the answers

What is the primary site of action of inorganic Hg salts?

Proximal tubular cells Signup and view all the answers

What is the effect of CH3Hg on the nervous system?

Affects the nervous system, with fetal brain being more sensitive Signup and view all the answers

What is the result of Hg binding to SH groups of membrane proteins?

Decreased membrane integrity Signup and view all the answers

What is Minamata disease?

A type of neurological disorder caused by Hg poisoning Signup and view all the answers

What is the effect of acute Hg exposure on the body?

Causes a range of symptoms including cough, sore throat, and abdominal pain Signup and view all the answers

What is the effect of chronic Hg exposure on the body?

Causes permanent damage to the central nervous system and kidneys Signup and view all the answers

How can Hg affect the fetus?

Hg can cross the placenta, and may affect the fetus Signup and view all the answers

What is the role of sulfate-reducing bacteria in the environment?

They convert inorganic Hg to CH3Hg Signup and view all the answers

Study Notes

Metal Toxicity

Metals can cause toxic effects by interacting with cellular targets, specifically biochemical processes and subcellular membranes, leading to enzyme inhibition/activation and endocrine/reproductive disorders.
Common mechanisms of metal toxicity include:
- Enzyme inhibition/activation by metal-binding to sulfhydryl (SH) groups.
- Disruption of organelle structure and function, particularly neurotoxicants.
- Carcinogenicity and accumulation in the kidney.

Metal-Binding Proteins

Metallothionein (MT) is a metal-binding protein that regulates intracellular bioavailability of metals like Cd, Cu, Hg, Zn, and Ag.
Ligands with many SH binding sites can outcompete other intracellular proteins, mediating metal bioavailability and toxicity.

Exposure to Toxic Heavy Metals

Classification of exposure:
- Acute: ≤ 14 days
- Intermediate: 15-354 days
- Chronic: > 365 days
Modes of exposure:
- Accidental spills, careless handling, or living near hazardous waste sites.
- Contaminated food, air, water, or dust.

Arsenic

Arsenic is a metalloid that can be organic (combined with C and H) or inorganic (combined with other elements like O, Cl, and S).
Arsenic is associated with ores containing metals like Cu and Pb, and can be released into the environment through smelting, manufacturing, and other processes.
Arsenic compounds occur in three forms: pentavalent (As+5), trivalent (As+3), and arsine gas (AsH3), which is the most toxic form.
Arsenic can be difficult to detect in food, water, or air, and can accumulate in fish and shellfish.

Cadmium

Cadmium (Cd) accumulates in the kidney, where it binds to metallothionein (CdMT) and disrupts lysosomal function, leading to cell injury.
Cd can replace phosphorus in bone tissue and be stored for years.

Mercury

Mercury exists in three forms: elemental (Hg0), inorganic (Hg+ and Hg2+), and organic (CH3Hg).
Elemental mercury can be generated naturally from the earth's crust, volcanic emissions, and human activities.
Organic mercury is highly toxic and can cross membranes, affecting the nervous system, particularly the fetal brain.
The Minamata disease (1950s) was a large episode of mercury poisoning, resulting in deaths and cases of cerebral palsy-like symptoms.

Health Effects of Mercury Exposure

Acute exposure: symptoms include cough, sore throat, shortness of breath, abdominal pain, nausea, vomiting, diarrhea, headaches, weakness, visual disturbances, tachycardia, and hypertension.
Chronic exposure: permanent damage to the central nervous system and kidneys, and potential effects on the fetus.

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Description

This quiz explores the toxic effects of metals, including their interaction with cellular targets, biochemical processes, and enzyme inhibition or activation.