General mechanisms by which toxins damage cells (oxidative stress, enzyme inhibition, membrane disruption) tested at the introductory toxicology level.
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- What is oxidative stress?
- An imbalance between reactive oxygen species production and antioxidant defenses, favoring damage.
- What are reactive oxygen species (ROS)?
- Chemically reactive molecules containing oxygen, such as superoxide and hydroxyl radical.
- What is a free radical?
- A molecule with an unpaired electron, making it highly reactive.
- What is the primary intracellular antioxidant that protects cells from oxidative damage?
- Glutathione (GSH).
- What happens to a cell when its glutathione stores are depleted by a toxin?
- The cell becomes more vulnerable to oxidative damage.
- What is lipid peroxidation?
- Oxidative degradation of lipids in cell membranes by free radicals.
- What is the main consequence of lipid peroxidation for a cell membrane?
- Loss of membrane integrity and increased permeability.
- How does carbon tetrachloride cause liver cell injury?
- It is bioactivated to a trichloromethyl free radical that triggers lipid peroxidation.
- What is enzyme inhibition as a mechanism of cellular toxicity?
- A toxin binds to an enzyme and blocks its normal catalytic activity.
- Organophosphate pesticides inhibit which enzyme?
- Acetylcholinesterase.
- What happens when acetylcholinesterase is inhibited?
- Acetylcholine accumulates at synapses, causing overstimulation.
- How does cyanide poison cells?
- It inhibits cytochrome c oxidase (complex IV), blocking cellular respiration.
- What is the result of cytochrome c oxidase inhibition by cyanide?
- Cells cannot use oxygen to produce ATP, causing histotoxic hypoxia.
- How does carbon monoxide impair oxygen delivery to tissues?
- It binds hemoglobin with much higher affinity than oxygen, forming carboxyhemoglobin.
- What is membrane disruption as a toxic mechanism?
- Damage to the structural integrity of the cell membrane, causing loss of its selective permeability.