class 7 Flashcards
What historical figure is associated with symptoms caused by mercury exposure in the hat-making industry?
The “Mad Hatter” character from Lewis Carroll’s “Alice’s Adventures in Wonderland” is associated with symptoms such as tremors and hallucinations, known as “Mad Hatter’s disease,” caused by mercury nitrate used in the felting process.
What are the primary forms of mercury in the environment, and how is methylmercury formed?
Mercury exists in several forms: elemental (Hg⁰), inorganic (Hg²⁺ and Hg⁺), and organic (methylmercury, MeHg). Methylmercury is formed when mercury is converted by microorganisms in water bodies.
How does methylmercury enter and biomagnify in the food chain?
Methylmercury enters the aquatic food chain, starting with phytoplankton, and biomagnifies at each trophic level, leading to the highest concentrations in top predators like large fish.
What is the mechanism by which methylmercury is absorbed and distributed in the human body?
Methylmercury is well absorbed from the gastrointestinal tract (estimated at 95% from fish), distributed to all tissues, including the brain, and accumulates in hair. It’s primarily excreted through feces.
Explain how methylmercury uses cysteine to cross the blood-brain barrier.
Methylmercury binds to the amino acid cysteine, forming a complex that mimics methionine. This allows it to trick transport systems, like the LAT1 transporter, to cross the blood-brain barrier and enter the brain.
methylmercury has a clever trick. It puts on a disguise by grabbing onto a helper named cysteine, which normally gets a free pass into the brain because it’s good for you. When methylmercury holds onto cysteine, it looks just like another good guy the brain needs, so the guard lets it through the gate.
Describe the role of oxidative stress in methylmercury-induced neurotoxicity.
Methylmercury induces oxidative stress by binding to glutathione (GSH), impairing its antioxidant function, and interfering with the mitochondrial respiratory chain, leading to increased production of reactive oxygen species (ROS) and cellular damage.
How does methylmercury exposure affect motor performance and oxidative stress in the brain?
Methylmercury preferentially targets the cerebellum, leading to motor performance deficits and increased oxidative stress, which may explain the observed impairments in individuals with methylmercury poisoning.
What effects does methylmercury have on brain development, particularly in fetal exposure?
Methylmercury crosses the placental barrier, affecting fetal brain development even at low levels, leading to decreased IQ, impaired movements, visuospatial perception deficits, and speech impairments, known as Fetal Minamata disease.
How does methylmercury disrupt neuronal migration during brain development?
Methylmercury may bind to proteins crucial for neuronal structure and movement, such as actin and cell adhesion molecules (CAMs), disrupting the neuronal migration process essential for proper circuit formation and leading to cognitive and movement impairments.
What strategies have shown potential in counteracting the negative effects of methylmercury exposure?
Consumption of fruits rich in antioxidants, such as acai, has shown potential in counteracting the negative effects of methylmercury exposure by reducing oxidative stress and improving motor performance.
What caused “Mad Hatter’s disease” in the hat-making industry?
Hat makers were exposed to mercury, which caused symptoms like shaking and hallucinations.
What happens to mercury when it gets into water bodies?
Tiny organisms in water turn mercury into methylmercury, a toxic form that builds up in fish.
How does methylmercury move up the food chain?
It starts in small water plants and moves up to big fish and animals, getting more concentrated at each step.
How does our body deal with methylmercury from fish?
Our stomach absorbs almost all of it, it spreads through our body, and can even get into our brain. It mostly leaves our body through poop.
How does methylmercury trick its way into the brain?
It attaches to a protein called cysteine, disguising itself as something the brain needs, so it gets let in.
What does methylmercury do to the brain’s defense system?
It grabs onto the brain’s cleanup crew, glutathione, stopping it from getting rid of harmful substances.
Why is methylmercury bad for our brain cells?
It creates too many harmful oxygen particles that damage cells, a bit like rusting metal.
How does methylmercury exposure affect movement?
It damages the part of the brain that helps control movement, leading to problems like clumsiness.
What’s so bad about babies being exposed to methylmercury?
It can harm the developing brain, leading to problems with IQ, movement, seeing shapes, and talking.
Can eating certain foods help against mercury damage?
Yes, foods high in antioxidants, like acai berries, can fight the damage mercury causes in the brain.
Why is mercury used in gold mining, and what environmental problem does this cause?
Mercury is used to extract gold from ore because it binds to gold, forming an amalgam. This causes environmental problems when mercury vapor is released into the air or when liquid mercury enters waterways, leading to contamination and toxic exposure for wildlife and humans.
How does methylmercury affect pregnant individuals and their unborn children differently from others?
Methylmercury crosses the placenta and can harm the developing brain of the fetus, leading to more severe and lasting impacts than in adults, including lower IQ and developmental delays, even at lower exposure levels.
What is “Minamata disease,” and how did it reveal the dangers of methylmercury?
Minamata disease is a neurological syndrome caused by severe mercury poisoning, identified in Minamata, Japan, where industrial wastewater contaminated local seafood. It highlighted the toxic effects of methylmercury on humans, especially the devastating impact on fetal brain development.
Explain the global mercury cycle and why mercury pollution is a worldwide concern.
The global mercury cycle describes how mercury moves through the environment, from air to water to living organisms. It’s a concern because mercury released in one place can travel long distances through the atmosphere, contaminating areas far from the original source and affecting global health and ecosystems.
